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Proceedings of the Chemical Society. May 1962 |
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Proceedings of the Chemical Society ,
Volume 1,
Issue May,
1962,
Page 165-196
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PROCEEDINGS OF THE CHEMICAL SOCIETY MAY 1962 LIVERSIDGE LECTURE* Stereospecific PoIymerisation By C. E. H. BAWN (THEUNIVERSITY, LIVERPOOL) ALTHOUGH the occurrence of stereoisomerism in the vinyl polymers had long been recognised it was not until the last few years that methods were discovered for the synthesis of stereoregular polymeric mole- cules. Schildkneckt in 1948 described two forms of polyvinyl isobutyl ether one of which was crystalline and recognised as stereoregular in structure. Little attention seem to have been paid to the develop- ment of this discovery until Natta showed that the catalysts developed by Zeigler for the polymerisa- tion of ethylene at room temperatures and pressures could be used to prepare crystalline polypropene and other crystalline polyolefins.Since 1955 progress in this field-which has been important and significant both in regard to the fundamental and the techno- logical science of polymers-has been so rapid and is still continuing at such a rate that even today it is difficult to present a true up-to-the-minute picture of progress. It has thus been necessary to restrict the scope of this Lecture to the methods of synthesis of stereoregular polymers and in particular to the nature of the catalyst used and the mechanism of the reaction. Other aspects of this subject such as mole-cular structure and properties of stereopolymers measurement of tacticity technological applications etc. which have shown equally spectacular develop- ments and each of which could itself be the subject of a lecture have had to be omitted.Nattal recognised two regular arrangements dis-tinguishable by the disposition of units on the polymer chain. He defined an isotactic polymer as having every asymmetric carbon atom in the main polymer chain with the same configuration i.e. having asymmetric carbon atoms with an all (+)-configuration or an all (-)-configuration. Syndio-tactic polymer molecules have alternate asymmetric carbon atoms with the same configuration. Atactic polymer molecules have a random arrangement of asymmetric carbon atoms. More recently Natta2 and Breslow3 and their collaborators have succeeded in polymerising 1,2-di- substituted ethylenes of the type CHR=CHR’. This kind of monomer gives rise to polymer molecules with two different asymmetric carbon atoms in the backbone chain and consequently the original definitions of the various tactic modifications have been extended by Natta Farina Peraldo and Bressau,* as indicated below.When the two different asymmetric carbon atoms in the polymer chain occur with the same configuration the polymer is called erythro-di-isotactic (Fig. 1). If the two asym- metric carbon atoms have alternating configurations * Delivered before The Chemical Society on December 14th 1961 at the Royal Institution London W.1 on March lst 1962 at Leeds and on March 2nd 1962 at Exeter. Natta J. PoZymer Sci.,1955 16,143. a Natta Makromol. Chem. 1960,45,93. Vandenberg Heck,and Breslow J.Polymer Sci. 1959,41 518. Natta Farina Peraldo and Bressau MakrornoZ. Chem. 1961 43,68 281 cf. Natta Farina and Donati ibid. p. 251. 165 the polymer is said to be threo-di-isotactic (Fig. 1). The erythro-polymer will be obtained by stereo-specific polymerisation of a trans-1 ,Z-disubstituted ethylene and the threo-derivatives will arise from a similar polymerisation of the corresponding cis-olefin. FIG.I. ctyehto-di -isotactic HHHHH lhm-d i-isotactic The diolefins give rise to stereoisomerism and also to geometrical isomerism. Butadiene for example gives rise to five types of polymer three of which are the isotactic syndiotactic and atactic modifications of polybuta-l,2-diene. The other forms arise from 1,4-addition to the monomer molecule and this of course produces an unsaturated carbon backbone in which the unsaturated linkages can have either a cis-or a trans-conformation viz.With isoprene and chloroprene the situation is further complicated by the possibility of 3,4-modes of polymerisation. In polymers of penta-l,3-diene having l,knchainment both stereo-and geo-metrical isomerism occur the chain units may be cis-or trans-forms and each tertiary carbon atom (+I or (-1. Natta and his collaborators4 have succeeded in obtaining crystalline polymers from methyl ethyl and butyl trans-trans-sorbate and from methyl 5-phenylpenta-2,4-dienoate. All these monomers have the general structure HH It HH on polymerisation by 1,6addition they yield poly- mers -[*CHR-CH =CH.*CH(CO,R’)],- in which Price and Osman.J. Amer. Chem. SOC..1956.78.4787. PROCEEDINGS each repeating unit has three centres for steric variation. The original workers suggested the general name tritactic for this type of polymer although to date only one modification has been isolated namely that thought to have the structure (I),which Natta has named erythro-di-iso-trans-tactic. In addition to the a-olefins the dimes and the wide range of vinyl monomers other important monomers which have been polymerised to stereo- specific configurations include the alkylene oxides5 of type (11),aldehydes,6 and ketens,’ RR‘C=C =O. These give polymers with repeating units (III)-(VI) respectively. As with the polyolefins isotactic and* syndiotactic forms are theoretically possible in each case.Optical Activity in Stereoregular Polymers.-In a homopolymer the differences in structure between the two chains of the polymer attached to any asym- metric centre are limited to end groups and these would be expected to cause a negligible optical acti- vity since the environment immediately round the asymmetric centre is so similar. Further if the poly- mer chains were comprised of all (+) and (-) centres then each asymmetric carbon atom would have a mirror image on the opposite side of the central carbon atom of the main chain. It is how- ever unlikely that the chains will be built of (+)-and (-)-centres exclusively and the large molecules will normally contain chain sequences of (+)-and (-)-centres of various lengths.If on the other hand the near environment of the asymmetric carbon atom is grossly dissimilar then optical activity would result as for example in the isotactic polyalkylene oxides. Price and Osman5 were the first to make an optically active polymer; they started with an optically active monomer propylene oxide but more recently Pino and Lorenzis obtained optically active Natta Corradini; and Bassi J. Polymer Sci.. 1961,51,305; Furakawa Saeguso and Fugii Makromol. Chem. 1961 44 398; Vogl J. Polymer Sci.,1960,46 261. Natta Mazzanti Pregaglia and Binachi Makromol. Chem. 1961 4-46,537. 13 Pino and Lorenzi J Amer. Chem. SOC.,1960,82,4745. MAY1962 isotactic vinyl polymers starting from one of the enantomeric forms of asymmetric monomers (3-methyl pent -1 -ene 4met h ylhex- 1-ene 5-me th ylhept -Z-ene and 2-methylbutyl vinyl ether).They observed a remarkable increase in optical activity in com- parison with that for asymmetric compounds of low molecular weight having similar structures. Similar results were obtained by Bailey and Yatesg who also showed that the activity was lost when the side groups were removed. Pine and Lorenzi ascribed the enhanced optical activity of the polymer to the pre- ferred skew sense of the main chain induced by the presence of the asymmetric side substituent. Some interesting examples of asymmetric syntheses of high polymers have recently been described by Natta and his co-~orkers.~ Tritactic polymers pre- pared from monomers which do not contain asym- metric carbon atoms viz.alkyl sorbatesl and 5-phenylpentadienoates have been shown to be optical-ly active if the catalyst used in the polymerisation reactions either contained an asymmetric centre for instance (R)-2-methylbutyl-lithium or was in the form of a complex with an active Lewis base for instance (-)-menthy1 ethyl ether. Similarly benzo- furan polymerised with ethylaluminium dichloride at -80" to -100" gave an inactive polymer but on using catalysts obtained by reaction or association of a metal-organic component with an optically active compound Natta obtained polymers of high optical activity. Finally optical activity may result if two different monomers are copolymerised in a stereoregular manner e.g.maleic anhydride and an active methacrylate monomer viz. Ye I + y CH,=7 CO2R Carbon atoms 1,2,and 3 in the copolymer backbone are all asymmetric centres and experiments indicatelo that the copolymer obtained from maleic anhydride and (-)-a-methylbenzyl methacrylate shows stereo- regularity in the backbone. The wider problem of asymmetric induction in polymer synthesis of which the above are examples has been fully discussed by Arcus.ll Stereoregulating Forces and Controlled Propagation. -It has become common practice to consider addi- Bailey and Yates J. Org. CJiern. 1960 25 1800. lo Beredjick and Schuerch J. Arner. Chern. SOC.,1956 78 l1 Arcus J. 1955 2801. l2 Bovey J. Polymer Sci.1960 46,59. tion polymerisation as free radical or ionic (cationic or anionic) according to the nature of the propagat- ing species. Zeigler polymerisation (a-ordination polymerisation) although ionic in character does not properly fit into conventional ionic classification and will be considered separately. Free-radical Propagation.-Of all the modes of propagation free-radical growth is best understood and is free from the complicating factor of solvation shells gegenions and complex-formation which play so important a role in ionic reactions. The free- radical end of a growing chain is the nearest approach to a freely propagating species and the growth re- action is the most readily amenable to theoretical treatment. Fig. 2 represents a typical step in the I sotac tic growth process and it will be seen that in the act of addition the configuration of the essentially planar free-radical end becomes fixed in either the isotactic or the syndiotactic configuration.If cx and /3 repre sent the relative probabilities of isotactic and syndio- tactic placement (a + b = l) then the ideal iso- or syn-diotactic polymer results when cx = 1 or = 1 respectively and the completely random polymer when a = = &.The Figure shows that if X is a bulky group then steric effects alone will in general favour syndiotactic placement. If the propagation reaction is controlled entirely by steric interactions that is no other agency controls the position taken up by the incoming monomer then reaction will be independent of solvent concentration and conversion but in general will be temperature-dependent.The higher the temperature the less significant will be the small energy difference between the alternative place- ment so that both a and /3 tend towards +.At lower temperatures steric factors favour the syndiotactic placement ,8 and the effect may be large enough to permit the formation of a crystallisable polymer. A very detailed study of the polymerisation of methyl methacrylate by Bovey12 confirms the view that the syndiotactic propagation becomes increasingly domi- nant as the polymerisation temperature is lowered. 2646. Bovey found that the difference in activation energy for the isotactic placement was 775 f 7 cal./mole (i.e.,mole of monomer) greater than for the syndio- tactic placement.Similar results were obtained by Bawn Janes and North13 for the low-temperature free-radical polymerisation of methyl methacrylate initiated by ethylsilver and by Fordham and his co- worker~~~ for polymerisation of vinyl chloride and of chlorinated and fluorinated vinyl acetate. Fordham et al. made a theoretical study of the relative im- portance of the steric and the electrostatic com- ponent of the relative potential-energy level for the two possible configurations and his experimental results support the theoretical estimate of activation- energy difference of about 0.5 kcal./mole in fmour of the syndiotactic form. For highly polar monomers such as fluorinated or chlorinated vinyl esters the results suggest that the electrostatic becomes more important than the steric factor in regulation of the structure of the polymer.In these cases only the syndiotactic polymers were obtained and the authors suggest that the syndio- tactic propagation may be preferred for all radical polymerisations. More recent syntheses of the syndio- tactic polymers of methyl methacrylate isopropyl acrylate and cyclohexyl acrylate support this view.15 Ionic Polymerisations.-Po1ymerisations involving ionic intermediates are subject to several stereo- regulating forces which do not occur in typical free- radical polymerisation the most important of which is the influence of the attendant gegenion. Unfortu- nately the influence of gegenions on reaction rates and stereochemistry are all too little understood.The best approach to such problems is undoubtedly to consider each ion-pair as being able to exist in several distinct forms depending on the degree of separation. Winstein and his collaborators16 have formulated such a scheme for ionisation leading to carbonium ions viz. RX *_ R+X-LR+/X' % R++x-CQWlent Int imate Solvent Free ions r ion-pair ion-pair Of course such a general scheme for ionisation does not take into account any specific solvation effects or salt effects on either component of the ion-pair but it suffices to point out that in solvents of low dis- sociating power ionisation will most probably lead to intimate ion-pairs.Cationic Polymeris~tian.-Although it was not then PROCEEDINGS realised cationic polymerisation provided the first synthesis of an isotactic polymer. In 1948 Schild-knecht showed that crystalline polymers could be obtained from isobutyl vinyl ether and later from other branched-alkyl vinyl ethers by using the boron trifluoride-ether complex as catalyst undar heterogeneous conditions. More recently Japanese worked' have extended his observations and shown unambiguously that the stereospecific polymerisa- tion can proceed under homogeneous conditions. By suitable choice of mixed solvents the whole reaction can be maintained and homogeneous and stereo- specific polymers of isobutyl vinyl ether and methyl vinyl ether readily obtained. In all cases where crystalline polymers are produced the reaction temperature was necessarily very low (ca.-70°) and crystallinity decreased as the reaction tempera- ture increased. Nattals has recently shown that crystalline iso- tactic alkyl vinyl ethers can be obtained by many different catalysts both homogeneous and hetero- geneous in nature. In most cases the solvent used was toluene and homogeneous stereospecific polymerisa- tion of isobutyl vinyl ether resulted when the follow- ing catalysts were used AIEt,CI AlEtCI, TiCI,(OC,H,),. In each case the polymerisation tem- perature was around -78' and similar results were obtained when using the soluble crystalline com- plexes (C,H,),TiC1,.AICI2 and (C5H5),TiCI2*A1C1Et. Examples of cationic polymerisation to stereo- specific structures are largely confined to the vinyl ethers.However Nattal* has recently reported that the etherate complexes of boron trifiuoride and aluminium bromide polymerise aldehydes at -40" to -100" to very stereospecific molecules and also that 2-methoxystyrene unlike styrene is polymerised homogeneously and cationically by AIC1,Et to an ordered non-crystallisable isotactic polymer. The various mechanisms proposed for the homo- geneous stereospecific polymerisation of alkyl vinyl ethers assume that the presence of a gegenion near the charged carbon atom of the last monomer unit modifies the electron configurahn of this carbon in such a way that it is not adequately described as sp2(trigonal)-hybrids but rather as sp3(tetrahedral)- hybrids especially in solvents where dissociation of the ion-pair does not take place to an appreciable extent.Bawn and Ledwithlg believe that mesomerism in vinyl ethers would lead predominantly to the trans-form. If this form of vinyl ether predominates Bawn Janes and North J. PaIymer Sci.,in the press. l4 Fordham McCain and Alexander,J. Polymer Sci. 1959 39 335. l6 Garrett Goode Gratch Kincaid Leverque Strongse and Watanabe J. Amer. Chem. Soc. 1959 81 1007. la Winstein and Robinson J. Amer. Chem. Soc. 1958 80 169. Okamura Higashimuia and Sakurada J. Polymer Sci. 1959 39 507. Natta J. Polymer Sci. 1960 9,219. l8 Bawn and Ledwith,Pofymer 111 the press. MAY 1962 then it becomes clear that when the alkyl substituent contains at least three consecutive carbon atoms substantial steric blocking of one side of the olefinic bond will occur for example (W9.The steric block- ing will be greatest for neopentyl vinyl ether and will decrease through isobutyl and n-propyl vinyl ether; for isopropyl vinyl ether and ethyl vinyl ether such steric blocking is not possible.These predictions are substantiated by examination of molecular models and coincide with the experimental observation that isobutyl vinyl ether readily yields crystalline polymer whereas isopropyl vinyl ether does not. Now the growing cation can be stabilised by a form of neighbouring-group interaction or intra-molecular solvation through the oxygen atoms in the penultimate monomer unit (formation of a four-membered ring) or more probably through the formation of a six-membered ring with the oxygen atom of the last-but-three monomer unit as shown in Fig.3. Such intramolecular solvation or stabilisa- tion of the growing cation will obviously lead to reactions at the cation which involve attack from the opposite side i.e. that side on which the gegenion is found. The polymerisation of alkyl vinyl ethers by this mechanism is shown in Fig. 3 and examination of molecular models shows that the preferred mono- mer conformation is likely to be that shown in Fig. 3. However this conformation differs only slightly from several others and the small differences in acti- vation energy between these various monomer-approach conformations will become significant only at low temperatures.This will lead to an increase in stereospecifici ty with decrease in reaction tempera- ture. Anionic PuZymerisatiun.-This is usually initiated with a carbanion or alkoxide ion which adds directly to the double bond R-+ CH,=CHX + R-CH,-CHX-RO-+ CH,=CH.CH + RO-CHz-CH(CH,)-O-169 or by electron-transfer from an electron-donor D or D-D+M-tD++M-D-+M-+D+M-where M is the monomer and M-the primary ion- radical formed in the initiation process. Typical initiators are the alkyls of the alkali metals sodium naphthalene and similar complexes Grignard re agents and hydroxyl and alkoxide ions. The organo- metallic catalysts have been very effective in the preparation of stereoregular polymers of styrene acrylates acrylamides and other vinyl monomers having electron-withdrawing substituents.A repre-sentative selection of recent polymerisation results is summarised in Table 1. The prominence of alkyl- lithium as initiators is very evident and we shall con- sider the general features and mechanism of this type of polymerisation in some detail. The alkyl-lithiums like organomagnesium com- pounds are associated in solution but much recent evidence indicates that it is the monomer species which is the true initiator.20s21 The properties of the organoalkali compounds are consistent with a type of metal-carbon bond intermediate between a co- 6+ 6-valent bond highly polarised in the M -+R direction to an extent dcpending on the electronegativity and polarisability of both the organic radical and the alkali metal.Some of these compounds may even be regarded as fully ionised M+R-. Because of the small size and high polarising power of the lithium ion lithium compounds have more covalent character than have the other alkali metals. The greater solu-bility in hydrocarbons and the smaller reactivity of alkyl-lithiums is a result of the lower polarity of the Li-C bond. The ionisation of this bond can be repre sented by the scheme previously discussed (p. 168). In hydrocarbon solvents the alkyl will exist as in the covalent form and as intimate ion-pair; the solvent ion-pair and free ions are likely to prevail in more solvating solvents such as ethers and amines.Temperature will also affect the equilibrium between the two ion-pairs. In polar and solvating solvents anionic polymerisa- 2o Margerison unpublished work. Worsfold and Bywater Canad.J. Chem. 1958 36 1141; J. 1960 5234. tion would be expected similar to that discovered by Szwarc22 when using sodium naphthalene as initiator. The polymeric anion could be regarded as a free propagating species and the requirements for stereo- specific polymerisation would be similar to those previously formulated for free-radical initiation viz. greater stereoregularity would occur on poly- merisation at lower temperatures and syndiotactic placements would be preferred. Experimental obser- vations with several monomers (see Table 1) substantiate this conclusion.PROCEEDINGS The driving force for propagation is an initial complex-formation or co-ordination between the lithium atom in the covalent and intimate ion-pair form and the n-electron system of the monomeric olefin. The most probable approach conformation is shown in Fig. 4. Co-ordination of the olefin will be followed by an intramolecular rearrangement in- volving migration of the carbanion R-to the most electrophilic carbon atom of the unsaturated mole- cule. The product of this reaction will then be another alkyl-lithium molecule possessing covalent TABLE1 Monomer Me methacrylate Styrene NN-Disu bs ti tuted Catalyst BunLi Huorenyl-lithium BunLi Temp. -40" -90" to +100" 25 -30 Solvent Polar Non-polar Ethers Weakly polar Hydrocarbons Polymer Syndiotactic Is0 tactic Atactic Block copolymer Isotactic Ref.a b acrylamides Me methacrylate EtLi Grignard reagent linear-alkyl bromide branched-alkyl bromide Hydrocarbon Tacticity de- creases with increase in Isotactic Isotactic Stereoblock C d 2-Vin ylpyridine Et2N*MgCl MgEt2 PhMgBr :Et20=4 1 PhMgBr :C,H,N =2-5 :1 45 9 9 , polarity Toluene 9 9 79 80-90 % Isotactic 90 % Isotactic No tacticity 40% 9 e Refs. (a) Goode et al. J. Polymer Sci. 1960 46 317; Fox et al. J. Amer. Chem. SOC.,1958 80 1768. (6) Kern, Nature 1960,187,410. (c) Butler Thomas and Tyler J. Polymer Sci.,1960,48 357. (d) Nishioka Watanabe Abe and Sono,J. Polymer Sci. 1960 48 241. (e) Natta et al. J. Polymer Sci.,1961 51 487. When reaction conditions favour structure the covalent and intimate ion-pair forms stereospecific polymerisation leads generally to isotactic structures.Isopropyl acrylate cyclohexyl acrylate and methyl methacrylate give isotactic polymers at -50" whereas the sterically hindered monomers such as t-butyl acrylate t-butyl methacrylate and NN-di- butylacrylamide yield isotactic polymers at room H FIG. temperature. Both the influence of solvent and temperature and the directing forces in stereoregula- tion can be readily understood in the following way 22 Szwarc Adv. Chem. Phys. 1959 11 147. or intimate ion-pair structure and the process will be repeated until either the monomer is used up or the metal-alkyl bond is deactivated in some manner. Once a simple alkyl-lithium has reacted with say methyl methacrylate in this manner the growing polymeric alkyl-lithium can then be expected to have some enolate character as shown in Fig.5 and ,Me 0-Me furthermore the lithium atom can co-ordinate in a six-membered ring with the carbonyl-oxygen atom of the penultimate monomer unit. Fig. 5 also shows MAY1962 the proposed mechanism of the polymerisation. Re- tention of configuration will be assured provided that the incoming monomer molecule always presents the same conformation towards the lithium atom. Examination of molecular models shows clearly that this condition is easily fulfilled for methyl methacryl- ate since of the two possible monomer conformations the one involving least steric interaction is that in which the a-methyl group in the monomer is in trans-position to the a-methyl group of the carbanion.Without the a-methyl group the last condition would not be fulfilled and methyl acrylate for example should prove difficult to polymerise stereo- specifically in this manner. been elucidated. Perhaps the most important recent observation is that the polymerisation of isoprene in hydrocarbon media catalysed by alkyl-lithiums gives a cis-1,4-poIyisoprene comparable with natural rubber. TabIes 2 and 3 summarise= the stereostruc- tures obtained with various alkali metals. It is apparent that metallic lithium is unique in producing mainly cis-1,.l-polyisoprene. Active solvents such as the ethers even in small concentration drastically modify the polymer structure.For example 0-5 part of tetraethylene glycol dimethyl ether per 100 parts of butadiene change the 1,2-content of the polymer from 12 % to 78 %. Table 3 taken from the work of Tobolsky and his co-workers,23 shows the effects of TABLE 2. Microstructure of polyisoprene catalysed by alkali metals and their organo-derivatives. cis- trans- Catalyst Li 194 ( %I 94.4 194 ( %)0.0 192 (%I0.0 394 (%I5.6 EtLi 94.2 0.0 0.0 5.8 BuLi 92.6 0.0 0.0 7.4 Na 0 43 6.0 51 EtNa 6.3 42 7.1 44.6 BuNa 4.1 34.9 6-7 54-4 K 0 52 8 40 EtK 23.7 39.2 5.7 31-4 BuK 19.6 40.8 6.2 33.5 Rb 5 47 8 39 cs 4 51 8 37 Alfin (Na) Emulsion 27 22 52 65 5 6 16 7 Cationic 36.7 50.6 3.8 8-9 EtLi 6.0 29.1 5-3 59.6 EtNa 0.0 14.3 10.2 75.6 Li 4.0 26.7 5-7 63-5 Polymerisation of Dienes by Alkali Metals and their Alkyl Derivatives.-Although it has been known for a long time that alkali metals and their alkyl deriva- tives polymerise dienes it is only recently that the detailed stereochemistry of the polymerisation has TABLE 3.Efect of tetrahydrofuran on the polymer microstructure. C,H,O/BuLi Polyisoprene structure 1,2 (%) 3,4 (%I 1,4 (%I 0 0 7 93 0-25 1 13 86 050 1 20 79 1 0 40 67 4 -32 8 -30 23 Tobolsky and Rogers J. Polymer Sci.,1959 40 73. small additions of tetrahydrofuran on the stereo- specific polymerisation of isoprene by lithium catalysts. Polymerisation initiated by metal dispersions pro- ceed with the intermediate formation of metal alkyls or alkenyls viz.Li + H,C:CMeCH:CH -+ LiCH,CMe:CHCH,Li LiR + H,C:CMeCH:CH -+ LiCH CMe:CHCH,R and the propagation step is Li-[CH,.CMe:CHCH,];R + H,C:CMeCH:CH -+ Li.[CH,-CMe:CH.CH,J,+l~R Growth occurs by successive insertion of the monomer at the metal-carbon bond. The high yield PROCEEDINGS of cis- 1,4-polyisoprene suggests a cyclic transition rationalised if one considers the relative ionic charac- ter of the alkali-metal organo-derivatives. The state in the polymerisation. Stearns and F~rman~~ have concluded that the alkyl-lithium adds to the cis-form of isoprene since spectral data indicate that ordinary isoprene contains 85 % of the cis-isomer at SO". The transition complex may be represented as a six-membered ring formed by reaction of the cis-isoprene with the carbon-lithium bond (Fig.6). The course of the reaction may be formulated as follows:As the monomer approaches the C-Li bond orbital overlap of carbon atom B and the lithium atom causes stretching and eventual breakage of the C-Li bond with the formation of a C-C covalent bond and regeneration of a new polar lithium-carbon Iinkage. Because of the intramolecular shielding on one side of the lithium atom further attack by a monomer molecule occurs on the opposite side giving a transition state similar to that of Fig. 6. Me H\ ' C=C H -Ha=' )i .........a*. $i Hi H2CA 'CH2 'c=c' "''Me\ Me H\ C=C1H Li+ F!G.6. -H,C' H't\' I H2C\ /CH< c=c H/ 'Me Although Raman spectra show that butadiene exists largely in the trans-form and the equilibrium mixture at 25" contains less than 4% of the cis-form polymerisation does not occur selectively to give a trans- 1,4-polymer in a hydrocarbon solvent.That polymer structure does not depend on polymerisa-tion temperature suggests that co-ordination com-plexes for both the cis- and the trans-form of buta- diene are not of very different stability. The experi- mental results indicate a different situation with iso- prene and it is probable that the trans-1,4-complex may be much the less stable or even difficult to form because of the steric influence of the methyl group. When the lithium-initiated polymerisation is per- formed in a solvating or basic solvent such as an ether and an amine the resulting polyisoprene con- tains mainly 3,4-linkages with about 25 % of trans- 1,4-1inkages.Similar structures result from poly- merisations initiated by other alkali metals even in hydrocarbon solvents. These observations are easily physical properties clearly establish the organo-alkali compounds as much more polar and dis- sociated than the corresponding lithium derivatives even in hydrocarbon solvents. We can imagine there- fore that the basic structure of these alkali metals approximates even in hydrocarbon solvents to the solvent-separated ion-pair structure proposed for a'kyl-lithiums in solvating media. Under these con- ditions the alkyl group is essentially a solvated anion and in diene polymerisation it will always be an alIylic anion.Co-ordination Catalysts fiom Transition-metal Com-poiinds (Ziegler Catalysts).-The original discovery by Ziegler related to catalysts for the low-pressure polymerisation of ethylene the most important of which was that obtained by admixture of triethyl- aluminium and titanium tetrachloride in a hydro- carbon solvent. Since the original discovery in 1953 an imniense amount of work has been done on this catalyst and other systems. Most of this is still un- published except in the patent literature which covers a vast number of variations on the original Ziegler catalyst. As a broad generalisation it can be stated that catalytic activity (of varying degree) is obtained by mixing alkyls or aryls of elements of Groups 1-111 of the Periodic System with com- pounds of the transition metals in Groups IV-VI.A characteristic feature of many of these catalysts is that they are insoluble complexes in which the lower valency state of the transition metal predominates. For a-olefin polymerisation Natta25 has shown that the most active and stereospecific catalysts are those formed by reaction between an alkyl of a highly electropositive metaI having a small diameter e.g. Be Al Li and a crystalline halide of a transition metal from Groups IV-VI in which the metal is in a valency state less than the maximum e.g. TiCl, VCI,. When the catalyst is prepared from the metal in a higher valency state e.g. from TiCl or VCI, the alkyl functions as a reducing agent leading to the reduced state of the metal.Organo-derivatives of titanium have been shown to be intermediates in this reaction and to function as Ziegler catalysts under certain conditions.26 In spite of the intensive study of these catalytic systems no precise and clear picture of the structure of the heterogeneous catalyst has emerged. The most widely accepted view is that the active catalyst sites consist of bridge structures of the type Et .Et., ,CL C,t/At: ".Et .**. Ti 'c[ a4 Stearns and Forman J. Polymer Sci. 1959 41 381. Natta Angew. Chem. 1955 67 541; 1956 68 393; J. Inorg. Nuclear Chem. 1958 8 589. *' Bawn and Gladstone Proc. Chern. Soc. 1959 227. MAY1962 ~~ ~ ~ ~ ~ ~ ~~ ~ ~ ~ Much of the work on the nature of the catalyst has been concerned with the polymerisation of ethylene.The outstanding work of Natta and his colleagues has extended the scope of these studies to the wider problem of the stereospecificity of reactions of the olefinic hydrocarbons CH,=CHR the dienes and non-hydrocarbon monomers. Investigations with the last class of compound are however very restricted because Ziegler catalysts such as TiCI and AIR react with monomers containing polar and reactive groups such as vinyl chloride acrylic esters and acrylonitrile. Before we consider the mechanism of the Ziegler type of polymerisation some of the more significant developments in the synthesis of stereo- specific polymers will be summarised since these will serve as a basis for discussion of the mechanism and as an indication of the scope of the subject and the immense progress which has been made in the last few years.The original Ziegler catalyst (TiC1,-AIR,) which was so effective with ethylene was not so satisfactory in the preparation of the stereoregular forms of the higher olefins. Greatly improved results were ob- tained by using the appropriate crystalline forms of the lower chlorides of metals (Table 4).279a These highly stereospecific catalysts function hetero-geneously and no soluble and homogeneous catalyst system has yet been found for the stereopolymerisa- tion of the a-olefins. TABLE 4. Influence of transition-metal cornpound and alkylaluminium on the yield of crystalline polypropene. Compound Alkyl Cryst.polymer (%) TiCl AlEt 48 AlPr 51 AIBu" 30 AIBu" 60 TiBr AlEt 42 TiCl (a) (y),or (8) AIEt 8&92 Al(CH &I) 96-98 BeEt 94-96 MgEt 78-85 ZnEt 30-40 NaR 0 Tic13 (PI AIEt 40-50 ZnC1 AlEt 55 VCI AlEt 73 CrCl AlEt 36 VCI AIEt 48 VOCl3 AlEt 32 Monoalkyl-metal dihalides and titanium tri-chloride do not provide stereospecific catalysts for a-olefins but if these catalysts are linked with 0.5 mol. of certain electron-donors or onium salts highly specific catalysts are produced2s (Table 5). TABLE5. Influence of additive to TiCI (a,p or 8) and AIEtX on yield of polypropene at 70". Stereo-index (% not extractable by ether Pyridine + 2A1EtBr2 or boiling heptane) 98.5 NEt + 2AIEtC12 95 NHEt + 2AlEtC1 93 NBu,l + 2A1EtBr2 >99 NBu,Br + 2AIEtC1 96 Although the major investigations on the influence of catalyst structure have been carried out with poly- propene most other a-olefins (straight or branched) styrene and substituted styrenes have been poly- merised by analogous catalyst systems.The polymers obtained from the a-olefins usually have the iso- tactic structure; the synthesis of syndiotactic poly- propene has however recently been announced although no preparative details are as yet available. Other than with the a-olefins the most successful application of the co-ordination catalyst has been to the polymerisation of butadiene and isoprene and other conjugated diene~.~.~~ The results (Table 6) show the highly specific nature of the catalyst as regards 1,2-or 1,4enchainment ratio of components and change of catalyst species.Co-ordinated catalysts have also been used to prepare cis-and trans-2,3-dimethylbutadiene,trans-piperylene and trans-polypenta-I ,4-diene. Of the several stereoisomers of the polypenta- 1,4-dienes only the isotactic trans-1,4-form has been syn-thesised. This polymer was amorphous owing to disorder in the configuration of the tertiary carbon atoms. Catalyst Structure and Mechanism of Polymerisation. -In discussing the mechanism of polymerisation by Ziegler catalysts we shall be mainly concerned with the growth reaction since this determines the high stereospecific nature of the reaction and exerts a more powerful controlling influence in this respect than either free-radical or simple homogeneous ionic polymerisation.As we have already seen many of the important catalysts function heterogeneously and the stereospecific nature of the reaction has been assumed in many polymer syntheses to be a direct consequence of the heterogeneous nature of the catalyst system. That the surface plays an important role cannot be disputed. However surface effects cannot be the sole stereoregulating force as many 27 Natta et al. Chimie et Industrie 1958 40 183; Gazzetta 1957 87 570. 28 Natta Pasquon Zambelli and Gatti J. Polymer Sci. 1961 51 387 399. 29 Natta J. Polymer Sci. 1960 48 219; Natta et al. Gazzetta 1959 89 761. PROCEEDINGS homogeneous catalysts have been reported for mono- mers other than the a-olefins.Broadly it appears that the catalyst whether homogeneous or hetero- geneous possesses two essential characteristics (a) one component of the catalyst must be a metal with vacant inner-shell d-orbitals and (b) the catalyst is organometallic and its structure with one possible exception,30 ClAl(NEt),-COCl, contains a carbon-metal bond. Before discussing some of the mechanisms which have been proposed it is con- venient to refer to the well-known established mode of formation of alkylaluminium compounds since diazoalkanes especially diazomethane with a variety of boron compounds as catalysts. They showed that the formation of a polymethylene chain occurred by the reactions R,B + CH,N -t R2B*CH2R+ N2 RZB'CHZR + KH2N + R,B*[CHJ,+,*R With diazoethane and the higher diazoalkanes stereoregular polyhydrocarbons were formed if the diazo-compound was decomposed by certain metal salts or metals.32 TABLE 6.Catalyst systems for conjugated dienes. Catalyst Butadiene cis-l,4- Polymer structure trans-l,4-1,2- 3,4- TiC14-AIR3 AI/Ti > 1 6 91 3 Al/Ti > 1 21-57 31-69 2-1 1 TiC13( a)-AIEt 5 87 8 TiCl,(P)-AIEt 37 603 TiCl ,@)-AIR ,Cl 55-60 36-41 4 TiBr,-Al(iBu) 88 3 9 Ti1,-AIR 93-94 1.5-2 45-5 CoCl,-AlR,Cl 96-97 2-5 1-1.5 Co st eara t e-AIR &1 98 1 1 VCl ,-AIR 3 99 1 VOCl3-AlRS 97-98 2-3 V C1 4-A1R 97-98 2-3 Ti(OBu),-AIEt 0-10 90-100 (VOAc),*-AIR3 Alp 'L 4 (unaged)AI/V 'L 10 (aged) MoO2(OR),-AlR, Al/Mo < 6 1-3 60 75 TiCI,-AlR, Al/Ti > 1 Isoprene 95 - 4 Al/Ti < 1 - 95 - 5 TiCl,( a)-AIEt - 91 I 9 VCl3-AlEt 3 - 99-100 - - V(A3)*-AlEt3 - - 90 * A this forms the basis of most of the proposed reaction schemes.Ziegler from his extensive studies of the reaction of alkylaluminiums with a-olefins especi- ally ethylene established the general growth reactions RtAI-R + CH,:CH -+ R,AI.CH,*CH,,R R2Al.CH2.CHZR + KZH + R2AI*[CHpCHa],-,*R Growth could also occur at each of the other two R-A1 bonds and thus three polyethylene chains could originate from each aluminium atom. A similar reaction was described by Bawn Ledwith and Matthies31 who studied the polymerisation of = Acetylacetone. Although various forms of bound free-radical mechanisms have been proposed for Ziegler catalysis the weight of evidence supports an ionic polymerisa- tion mechanism.The evidence for the ionic nature of the reaction has been fully summarised by Natta;= he bases his mechanism on the view that the active sites in a typical catalyst made from titanium or vanadium and aluminium alkyls constitute a bridged complex e.g. (VIII); he suggests that the titanium atom co-ordinates with the olefin. The driving force for the propagation is the co-ordination of the olefinic v-electrons with the vacant hybrid d-orbitals of the titanium the olefin adding to the aluminium-carbon 3o Montecathi Belgian P. 585,112/1959. 81 Bawn Ledwith and Matthies J. PoZymcr Sci. 1958 28 21. a* Bawn and Ledwith Chern. and Ind. 1957 1180; Nasini Troisarelli and Saini Mukromol.Chern. 1961,44 550. sa Natta J. Po2,vmer Sci. 1960 48 219. MAY1962 bond in the manner suggested by Ziegler viz. (IX) and (X). Natta 33 and Patat and Sinn,= have shown that this type of mechanism leads to stereoregularity if the complex compels the monomer always to assume the same orientation and the double bond opens in the same way-always cis or always trans. Since the terminal carbon atom of the growing chain is directly bound to an electropositive metal it assumes (at least in the activated state) a negative charge and Natta has called polymerisation of this kind "co-ordination anionic." ZiegleP5 has severely criticised the above mechanism on the ground that bridged complexes of titanium and aluminium are not likely to be involved in the growth reaction and he has repeatedly emphasised that the growth reaction does not occur with dimerised alkyl-aluminiums.Ziegler has also pointed out that alkyl-exchange occurs readily in solution and that equilibria such as AlAlkyi + TiAlkyl + AlTi alkyl complex may be set up. Some proposed mechanisms suggest that monomer addition occurs at the titanium- carbon bond of an organotitanium compound or complex the alkylaluminium serving as a source of alkyl groups. In pursuance of the detailed study of these reactions organotitanium compounds have been synthesised and their properties studied. Derivatives of quadrivalent titanium are unstable at room temperature and the decomposition products include free radicals.Thus North36 has shown that poly- merisation of styrene by phenyltitanium tri-iso- propoxide occurs by a free-radical mechanism. The initiation was observed to be due to interaction of the complex (RO),TiPh,Ti(OR) (which is similar in structure to a Ziegler catalyst) with the styrene monomer leading to free-radical chain-growth. On the other hand alkyltitanium trichlorides RTiCI (R = Me or Et) initiate the polymerisation of ethylene only after appreciable thermal decomposi- tion. This decomposition produces solid titanium 34 Patat and Sinn Angew. Chem. 1958,70,496. 35 Ziegler Angew. Chem. 1959,71,626; Chem. SOC.Spe&I s' North Proc. Roy. SOC.,1960 A 254,408. 37 Cossee Tetrahedron Letters 1960 No.17 12 17. 38 Uelzmann J. Polymer Sci. 1958 32,457. Bier Kuntstofe 1958 48 354. trichloride (RTiCI -+ R + TiCI,) and the true polymerisation catalyst is the complex of TiCI and TiC1,R. The obvious instability of alkyltitaniums seems to rule them out as active catalysts by them- selves but it is equally obvious that the aluminium or other alkyl in the presence of a titanium salt may function as an alkylating agent and serve to maintain the concentration of the true active species. These ideas have recently been incorporated by Cossee3; in a comprehensive scheme of the hetero- geneous polymerisation of a-olefins which has the special merit of explaining stereoregular growth at a crystalline surface. Cossee assumes that polymerisa- tion occurs at one titanium atom in the surface layer of a titanium trichloride lattice of which one surface chlorine atom has been replaced by an alkyl group R whilst an adjacent chlorine site is vacant and this accommodates the incoming monomer as in the annexed scheme.This leads to an active centre that retains a titanium-alkyl bond and a vacant site which however have changed places. Repetition of the process leads to isotactic polymers. The alkyl- aluminium is considered to act as a chain-transfer agent in re-establishing lost centres and as a scavenger for adventitious impurities but it is not considered essential for propagation. Cl Of the many other mechanisms proposed for Ziegler-type polymerisation those involving ion-pair structures for the catalyst complex which were first proposed independently by Uelzmann38 and BieP are in accord with many experimental observations.It is well established that alkylaluminiums and titan- ium tetrachloride form a deep red ionic complex when mixed at a low temperature. The structure of this complex has been formulated as -78" + -30" AIR + TiCl -+ Ct,TiAI~,CI -+ RTiCI Publ. 1959 13 1. PROCEEDINGS The various ion-pair mechanisms for polymerisation which function heterogeneously. Investigations with are typified by that of Uelmann viz. these systems are notoriously difficult and have certainly added to the problem of elucidating the fine details of the mechanism of stereopolymerisation of a-olefins and dienes. However effective homo- + geneous catalysts have been developed for dienes in Ti'CL A1 -R,CI ,cH,-CH particular and studies now in progress may throw t -TICL further light on the catalyst structure.H2C=CH R; CI The broad picture which has emerged from these studies is that the actual growth reaction takes place by co-ordination of the monomer with the transition CH,. CH2R CH,-CH,R metal. Whether the alkylaluminium actually forms Ti'CL AL-R/,Cl c-. TiCIi part of the catalyst complex or serves as a carrier to + AIR,Cl maintain the concentration of the unstable titanium alkyl if the latter is the true catalyst is still un- Summarising it is very difficult on the experi- decided. The various mechanisms which have been mental evidence available (which is largely derived proposed have much in common and each with some from the study of the heterogeneous polymerisation) slight modification could be incorporated into a to come to any firm conclusion as to the detailed general scheme.On the other hand it may well be course of the growth reaction. It was in some ways the case that this is asking too much and that Ziegler unfortunate that the initial and most significant dis- polymerisation occurs by several different but coveries of Natta were made with complex catalysts related mechanisms. COMMUNICATIONS Deuterium Exchange in rn-Dinitrobenzene By R. J. POLLITT and B. C. SAUNDERS (UNIVERSITY LABORATORY, CHEMICAL CAMBRIDGE) M-DINITROBENZENE and its derivatives give intense infrared spectrum is changed and shows a peak at colours with base in dimethylformamidel or di-23 13 cm.-l (C-D stretching).Proton magnetic methyl sulphoxide.2 These colours were originally resonance spectroscopy shows that replacement is attributed to quinonoid complexes. Spectroscopic largely confined to the 2-position the remaining studies show that several types of interaction occur protons giving an AB spectrum. This is confirmed and it seems likely that in some cases the coloured by the infrared spectrum where the C-H in-plane species is the ion formed by the removal of a proton vibration at 1065 cm.-l is replaced by the correspond- from the benzene ring. ing C-D vibration at 768 cm.?. An objection to this theory is that deuterium Under similar conditions 1,3,5-trinitrobenzene exchange is stated not to occur with 1,3,5-trinitro- undergoes very little deuterium exchange presum- benzene in 8~-sodium hydroxide3 or in ~yridine.~ ably owing to the greater stability of the trinitro- This has led to the rejection of proton-transfer as a benzene-OH-complex.Nevertheless the possibility possible mechanism for other colour reactions be-of proton-transfer cannot be dismissed in the poly- tween polynitrobenzenes and However we nitrobenzene series particularly for the complicated find that deuterium exchange does occur with secondary reactions which often occur.6 m-dinitrobenzene in dimethylformamideD,O in the presence of O-OOSN-sodium hydroxide. We are grateful to the D.I.S.R. for a maintenance The product has similar melting point analysis grant (to R.J.P.) and to Dr.N. Sheppard with whom and ultraviolet spectrum to the starting material. The we have had valuable discussions. (Received April 6th 1962.) Porter Analyt. Chem. 1955 27 805. Heotis and Cavett Analyt. Chem. 1959 31 1977. Ketelaar Bier and Vlaar Rec. Trav. chim. 1954 73 37. Miller and Wynne-Jones J. 1959 2375. Caldin and Long Proc. Roy. SOC.,1955 A 228 263; Ainscough and Caldin J.,1956 2540; Foster J. 1959 3508; Gold and Rochester Proc. Chem. SOC.,1960,403; Briegleb Liptay and Canter Z.phys. Chem. (Frankfurt) 1960,26,55. Foster and Mackie Tetrahedron 1961 16 119; 1962 18 161. MAY1962 177 Displacement of Ferrocene Substituents by Protons By I. G. MORRISON and P. L. PAUSON THEROYAL OF SCIENCE GLASGOW, COLLEGE AND TECHNOLOGY C.l) (CHEMISTRY DEPARTMENT CERTAIN electrophilic substitutions of aromatic systems are known to be reversible e.g.sulphona-tion Friedel-Crafts reactions. These “reverse” sub- stitutions involve electrophilic displacement of a substituent X by a proton. Important examples include the Jacobsen reaction1 in which alkyl groups or halogen atoms are displaced during sulphonation and the “detritiation” and “protodesilylation” studied by Eabom and his co-workers2 as an index of aromatic reactivity. We have now observed the displacement of chlorine atoms and of methoxy- and methylthio- groups from their ferrocene derivatives by protons. In Friedel-Crafts acetylations of chloro- (I; X = Cl) and methoxy-ferrocene (I; X =OMe) ferrocene was produced in the former and acetylferrocene in the latter case.That ferrocene was a likely intermediate in the formation of the acetylferrocene was demon- strated when methylthio- chloro- and methoxy- ferrocene were all found to give ferrocene on treat- ment with aluminium trichloride in methylene chloride at room temperature under nitrogen. Al- though dry hydrogen chloride itself failed to de- chlorinate chloroferrocene hydrogen chloride (formed in sufficient quantity from traces of moisture) must play a part in the reaction and it is tempting to assume that the known type3 of complex (II) is directly involved. If this can exchange X and H to Qx Qx Q Fe -H ‘Fe-X (1) @)@ give the cation (111) this may then react further according to one or both of the alternative schemes (1 2).In the case of chloroferrocene no dichloroderiva- tive was isolated and course (1) or some related mode of reaction must be followed. Methoxy- and methylthio-ferrocene however on treatment with aluminium trichloride afforded not only ferrocene but also mixtures of the isomeric dimethoxy- and di(methy1thio)-ferrocenes (by novel “methoxylation” and “methylthiolation” reactions). The second course must therefore be followed at least in part and the overall process may be described as a disproportionation. (Received March 29th 1962.) L. I. Smith in “Organic Reactions,” ed. Adams Vol. I Wiley New York 1942. Baker and Eaborn J. 1961 5077 and earlier papers. Rosenblum and Santer J.Amer. Chem. SOC.,1959 81 5517. The Crystal and Molecular Structure of Di-(L-histidino)zinc(Ir)Dihydrate By R. H. KRETSINGER and F. A. COTTON R. F. BRYAN OF BIOLOGY (DEPARTMENTS AND CHEMISTRY 1hdASSACHUSETTS INSTITUTE OF TECHNOLOGY CAMBRIDGE 39 MASS.,U.S.A.) DI-(L-HISTIDINO)ZINC(II) DIHYDRATE crystallises with space group P4,2,2 (P4,2,2) a = b = 7-53 c = 30.41 A. There are four molecules of the complex in the unit cell. 1100 of a possible 1290 independent reflections accessible to Cu-K radiation were recorded and visually measured. The positions of the zinc atoms were determined from a Patterson pr4ection P(u,O,w). The <TO-three-dimensional Fourier synthesis phased on the ordinates of the histidine residue were found from a contributions of the zinc atoms alone and were con- firmed from a three-dimensional Patterson synthesis.A second three-dimensional Fourier synthesis re- vealed the position of the water molecules. The usual reliability factor with unobserved reflections ex- cluded was 0.23 at this stage and was reduced to 0.15 by two rounds of full matrix least-squares refinement in which isotropic thermal parameters were used. A diagrammatic view of the molecule showing the PROCEEDINGS bond lengths at that stage of the refinement is shown Each N( 10) is intermolecularly hydrogen-bonded in the Figure; the bond angles are tabulated. to an O(5) (285 A). Each water molecule is assumed The zinc atoms located on a diagonal two-fold to be involved in hydrogen bonding to the O(4) axis are co-ordinated by two a-amino- N(l),and by atoms of two different chelate molecules (2.85 and C~N~CB 107" C7N8ZIl 125" N8CBNlo 107 C,N&l 128 CQNlOCll 110 C2NlZn 111 N10C11C7 lo5 C30,Zn 114 C11C7N8 110 N1ZnN8 96 CBC7Cll 125 N,ZnN, 121 C&N 125 N1ZnN8r 116 C2C& 114 N8ZnN8r 115 NlC2C6 109 N,Zn05 65 C&C 111 N1ZnO5l 71 CsC2N1 109 N,ZnO 82 04C3C2 118 N8Zn05r 163 05C3c2 122 O,ZnO,r 81 046305 120 2.72 A) and to serve as an acceptor in a hydrogen bond (2.85 A) to N(l) of a third chelate molecule.The possible existence of a fifth hydrogen bond intrachelate N( 1)-0(5') may be confirmed by subsequent refinement of the structure. two imidazole N(8) nitrogen atoms arranged in a somewhat distorted tetrahedral array.Two carboxyl- We gratefully acknowledge financial assistance oxygen atoms 0(5) approach the zinc closely from the National Institutes of Health and the enough to be considered loosely co-ordinated (2-80 National Science Foundation of the U.S.A. f0.05 A). (Received February 8th 1962.) The Crystal and MoIecular Structure of Di(histidino)zinc(n) Pentahydrate By MARJORIE and SABINA M. HARDING J. COLE (CHEMICAL LABORATORY ROAD,OXFORD) CRYSTALLQGRAPHY SOUTHPARKS WEhave determined by X-ray methods the crystal Zn(C6H8N302)2 5H20,prepared from DL-histidine. structure of di(histidino)zinc(rr) pentahydrate These crystals are monoclinic with a = 16-41,6 = 14.76 c = 10-99 A /3 = 129.6"; the space group is Q/c and there are four molecules per unit cell.The zinc atoms are on two-fold axes; the con- figuration of the molecules is similar to that described in the preceding Communication with zinc atoms in approximately tetrahedral co-ordination by nitrogen atoms at 2.00 and 2-05 A and with two carboxyl- oxygen atoms loosely associated (at 2.91 A). The water molecules take part in a system of hydrogen bonds which hold the lattice together. Three-dimensional data have been used. An aniso-tropic least-squares refinement of the parameters is nearly complete (R = 10.7%). We thank Dr. Bryan for showing us the preceding communication before submitting it for publication. Bond lengths and angles in the molecule of di-(D-We also thank the Rockefeller Foundation for a histidino)zinc(n).The molecule is viewed along the grant (to S.J.C.). two-fold axis. (Received January 15th 1962.) MAY 1962 179 Multiple Labelling Experiments in the Biosynthesis of Amaryllidaceae Alkaloids G. W. J. B. TAYLOR, By D. H. R. BARTON and G. M. THOW (IWERIALCOLLEGE S.W.7) LONDON RECENT investigations have shown that in agreement To show that bond a is not broken the work was with theory,l both tyrosine= and phenols of the repeated with triply labelled precursor (I; R = Me) general structure (1)2949798 can serve as precursors in with labels on 0-methyl N-methyl and the starred the biosynthesis of Amaryllidaceae alkaloids. It was carbon. Again incorporation only into galanthamine demonstrated* that the N-methyl labelled phenol (I; HO R = Me) and norbelladine (I; R = H) labelled as indicated were incorporated into galanthamine (11) with similar efficiencies in the King Alfred daffodil.In further work we have shown that the incorpora- tion of the labelled norbelladine (I; R = H) into galanthamine (11) proceeds without any “scrambling” of the label. The standard methodsg used will be detailed in our full paper. In all prior experiment~~p~,~*~9~ it has however not been proved that the phenolic precursors (as I) are not ruptured at bonds a and/or 6 before incorpora- tion into the final alkaloids. We now report experi- (0.018%) was observed. The relative activities of the ments (in King Alfred daffodils) with multiply three labelled positions in the precursor in galantha- labelled precursors which confirm that such fission mine and for confirmation in the derived narwedine does not precede incorporation.were identical (Table 1). TABLE 1. Fraction of 14C in Fraction of I4Cin Doubly labelled Me0 MeN Triply labelled Me0 MeN Remainder Precursor (I;= Me) 0.48 051 Precursor (I; R = Me) 0.19 0.21 0.60 R Galanthamine (11) 0.48 0.48 Galanthamine (11) 0.18 0.19 0.63 Narwedine 0-45 0.49 Narwedine 0.18 0.18 0.63 TABLE 2. Precursor (III) Galanthamine (II) Narwedine Me0 0.48 092 0.88 Fraction of 14C in { MeN 0.51 0.02 0.02 The phenol (I; = Me) was synthesised with The doubly labelled benzylamine (HI)(hydro-R both 0-and N-methyl labelling by standard chloride m.p. 169-1 72”) was incorporated into methods.e The incorporation into galanthamine galanthamine with complete loss of the N-methyl (0.014 %) galanthine (0.00%) and haemanthamine label but with the usual efficiency (0.019%) with (0.00%) were as in the earlier work.* The relative respect to the 0-methyl label (Table 2).This is in activities of the 0-methyl and the N-methyl groups agreement with the view5v6 that the aromatic ring of in the precursor the galanthamine (II) and for Amaryllidaceae alkaloids is derived from a C,-CI confirmation the derived (Mn02 oxidation) nar- fragment. Since the N-methyl label is lost in this wedine were determined as befores (Table 1). Clearly process the unit may well be of the isovanillin or bond b is not broken in the biosynthesis and also protocatechualdehyde type. selective demethoxylation does not occur.(Received March 12th 1962.) Barton and Cohen in “Festschrift Arthur Stoll,” Birkhauser Basle 1957 117. Barton and Kirby Proc. Chem. SOC.,1960 392. a Battersby Binks and Wildman Proc. Chem. SOC. 1960,410. Battersby Fales and Wildman. J. Amer. Chem. SOC.,1961 83 4098. Jeffs Proc. Chem. SOC.,1962 80. a Wildman Fales and Battersby J. Amer. Chem. SUC.,in the press. Battersby Binks Breuer Fales and Wildman Proc. Chern. SOC. 1961 243. Barton Kirby Taylor and Thomas Proc. Chem. Suc. 1961 254. Kobayashi and Uyeo,J. 1957 638. PROCEEDINGS Biosynthesis in the Amaryllidaceae Evidence for Intact Incorporation of Norbelladhe into Lycorine Crinamine and Belladine H.M. FALES,R.J. HIGHET,S.W. BREUER, By W. C. WILDMAN and A.R.BATTERSBY HEARTINSTITUTE U.S.A. and THEUNIVERSITY, (NATIONAL BETHESDA BRISTOL) TRACER studies have proved that tyrosine and R = CO-NHJand the aldehyde (11; R = CHO). derivatives of norbelladine (as I) act as precursors of The latter was oxidised to veratric acid which was several Amaryllidaceae alkaloids.l-’ However the decarboxylated. Hofmann degradation of belladine possibility existed that the precursors (I) were de methiodide yielded NN-dimethylveratrylamine,iso-graded in the plant to a C& unit which was then lated as the methiodide (IV)together withp-methoxy- (I) I.dOCt* (II) 0-22Ct (m)0*78C* (VII) incorporated. We now report evidence which proves styrene. The latter was converted by way of the in agreement with that norbelladine (I; R = dibromide (V) into the diol (VI) which was cleaved H) is incorporated intact into three alkaloids by periodate to formaldehyde and p-methoxybenz- occurring in Nerine bowdenii.aldehyde. The relative specific activities of these The synthesis of norbelladine (I; R = H) doubly Products are listed in the Table. labelled at positions 1’ and 1 used standard methods The radioactive crinamine (VII) was degraded as OH Ph 1 (x) o*23ct *CH 20 0-23Ctfor R=CO,H + o=nc* 0.22 C+ for R=H Phet CO,H 0-2I Ct (cf. ref. 5) which will be described in our full paper. for haemanthamine,3sG to 2-methyl-4,5-methylenedi-Methylation gave belladine (I ;R = Me) which was oxybiphenyl and N-toluene-p-sulphonylsarcosine. cleaved by cyanogen bromide to give the bromide (11; R = CH,Br)and the cyanamide (ILI; R = CN).Compound Relative activity These were converted respectively into the aldehyde Belladine (I; R = Me) 1-00 (11; R = CHO)and the urea (111; R = CO-NHd Veratric acid (11; R = CO,H) 0-23 m.p. 157-158” which had specific activities Carbon dioxide 0-22 showing that in the phenol (I; R = H) 22% of the me urea (111; R = CO.NH,J 0-76 activity is at position 1’ and 78 % at position 1. The methiodide (IV) 0.22 The alkaloids isolatedg from plants fed with the The dibromide (V) 0.76 doubly labelled phenol (I; R = H) showed the The glycol (VI) 0.70 following incorporations lycorine (0-07%) crina-Formaldehyde methone 0-73 mine (O.OO09 %) and belladine (2.64%). Degrada-p-Methoxybenzaldehyde (octahydro- tion of the belladine as above provided the urea (111; xanthen derivative) 0.00 l Battersby Binks and Wildman Proc.Chem. SOC.,1960 410. Barton and Kirby Proc. Chem. SOC.,1960,392. Battenby Fales and Wildman J. Ainer. Gem. SOC.,1961 83 4098. * Barton Kirby Taylor and Thomas Proc. Chem. SOC.,1961 254. Battersby Binks,Breuer Fales and Wildman Proc. Chem. SOC.,1961 243. Wildman Fales and Battersby J. Amer. Chem. SOC.,1962 84 681. Jeffs Proc. Chem. SOC.,1962 80. Barton and Cohen in “Festschrift Arthur Stoll,” Birkhauser Bade 1957 p. 117. @ Lyle Kieler Cpowder and Wildman J. Amer. Chem. SOC.,1960 82 2620. MAY1962 181 ~~ ~ ~ These contained respectively 22% and 78% of the activity present originally in the crinamine. The degradation of radioactive lycorine (V1I.I) followed our earlier w0rkl9~ and gave formaldehyde and the acid (IX; R = C0,H).The latter was decarboxylated and the resultant lactam (IX; R = H) was converted by phenyl-lithium into the phenanthridinium derivative (X) ; this was oxidised to benzoic acid. The relative activities shown under the formulae prove that lycorine (VIII) is specifically labelled at the indicated carbon atoms. The ratio of activities at the two labelled positions in the three alkaloids above is unchanged from that in the phenolic precursor (T; R = H); intact incor- poration is thus established and support is given to the view that phenolic oxidation is an important pathway in alkaloid bjosynthesis. (Received March 12th 1962.) Synthesis of ha ma me lose and its Epimer By J.S. BURTON and N. R. WILLIAMS W. G. OVEREND (CHEMISTRY DEPARTMENT COLLEGE MALET STREET LONDON W.C.1) BIRKBECK WE report the first syntheses of L-hamamelose (2-C-hydroxymethyl-~-ribose) (I) and 2-C-hydroxy- methyl-L-arabinose(11) by two different routes from an 0x0-sugar intermediate (111) which we have described previous1y.l Methyl 3,4-O-isopropylidene- 2-oxo-~-~-erythru-pntoside~ (111) was converted into methyl 2-C-hydroxymethyl-/?-~-arabinopyranoside (IV; R = CH,-OH) (via the 2-C-styryl derivative as described in ref. I) which on hydrolysis with an ion-exchange resin (H+ form) yielded the free sugar (XI) as a syrup [a] + 3.2" (in MeOH) [toluene-p- sulphonylhydrazone m.p. 158-1 59" (decomp.); a-benzyl-N-phenylhydrazone m.p.135-136'1. Compound (111) can be converted also into methyl 2-C-vinyl-/3-~-arabinopyranoside(IV ; R = CH:CH,) b.p. 134"/4 x lo4 mm. [aJg+ 169" (in EtOH) (by hydrolysis of its isopropylidene deriva- tive which was described in ref. l) which on hydro- lysis with the H+ form of an ion-exchange resin gave syrupy 2-C-vinyl-~-arabinose [a:] + 41 *2" (in MeOH). Reduction of this branched-chain sugar with sodium borohydride and purification of the product by chromatography finally afforded 2-C-vinyl-L-arabitol as a syrup [a] -358" (in MeOH) which after ozonolysis yielded the sugar (I) as a syrup { [a] + 6.3"(in MeOH)} indistinguishable chromatographicaIly from natural D-hamamelose. It formed a toluene-p-sulphonylhydrazone, m.p. 155-156" and p-nitrophenylhydrazone m.p.162-163" (the m.p. and [aID agree with those given by Freudenberg and Bliimme12). Alternatively a better yield of hamamelose was obtained by treatment3 of compound (111) with di- azomethane in methanol-ether (1 :1) at 0" which gave an epoxy-sugar (V) as a syrup b.p. 76"/0-1mm. [a] + 196" (in MeOH); on hydrolysis with N-sodium hydroxide and then 0.1N-hydrochloric acid this yielded methyl 2-C-hqdroxymethyl-/3-~- HO-$-H %-0 (I) HO-F-O-I,OH Hy-H HO3-H w2-0 (VI) ribopyranoside (VI) m.p. 133" (from ethanol). The residue from the mother-liquors afforded some of compound (IV; R = CH,-OH) from ethyl acetate- methanol (10 1). Hydrolysis of the riboside (VI) with ion-exchange resin (H+ form) yielded L-hamamelose (I) m.p.110-1 11 " (from ethanol-ethyl acetate) [a]E2 + 1.3" (3 min.) -+ +7-3" (equilib. after 17 min.) (by extrapolation [a] after zero time = -2.4") (in H,O). This is the first time that L-hamamelose has been obtained crystalline. Crystal- line D-form has not been reported. We thank the D.S.I.R. for a grant to J.S.B. (Received February 19th 1962.) Burton Overend and Williams Chem. and Znd. 1961 175. Freudenberg and Bliimmel Annulen 1924,440,45. Cf. Weygand and Schmiechen Chem. Ber. 1959,92 535. PROCEEDINGS The Absolute Configuration of I-Chlor0-3,4,4-timethylpenta-l,Zdiene By R. J. D. EVANSand S.R. LANDOR (WOOLWICH LONDON, POLYTECHNIC S.E.18) (+)-~,~,~-TRIMETH~PENT-~-YN-~-OL (I) has recently (+)-2-t-butyl-lactic acid hemihydrate [a] + 0.91O been converted into (+)-l-chloro-3,4,4-trimethyl-(this still contained some racemic acid and therefore penta-1 ,2-diene (cf.II) by an essentially stereospecific meth0d.l The absolute configuration of the (+)-chloride can be deduced if the absolute configuration of the (+)-alcohol is first determined. Preliminary considerations by Elie12 based on Brewster's theory3 predicted that the configuration of the (+)-alcohol is (S),and similar arguments had already led us to the same conclusion. More detailed arguments (which will be reported elsewhere) taking into account conformational asymmetry factors and interaction of the ethynyl and the hydroxyl group support this assignment. It has now been confirmed by the following more conventional method.Me OH Me-C-C-Me he C~H 01 The (-)-alcohol [a] -0-73",was converted by ozonolysis and oxidative hydrolysis with hydrogen peroxide into (+)-2-t-butyl-lactic acid (a-hydroxy- a@-trimethylbutyric acid) that crystallised as the hemihydrate m.p. 67-69' [a] + 1~39".~ The con- figuration of 2-t-butyl-lactic acid was established by asymmetric synthesis (cf. Prelog and earlier work by McKenzie5). Menthyl pymvate [a] -91 *6" and t-butylmagnesium chloride gave (-)-menthy1 2-t-butyl-lactate which on hydrolysis with sodium hydroxide solution gave a dextrorotatory crude acid fraction. Careful fractional crystallisation yielded Landor and Taylor-Smith Proc. Chem. Soc. 1959 154. Eliel Tetrahedron Letters 1960 No.8 16. had a dual m.p. 65-70' and 99-100'). t-Butyl-magnesium chloride attacks (-)-menthy1 pyruvate predominantly from the least sterically hindered side in each of the three staggered conformations (cf. Pre10g5). An excess of acid of (S-)configuration (HI) as shown wouId be expected in the product as this results from two of the rotational isomers whereas the (R)-acid (IV) is only obtained from one isomer and (+)-2-t-butyl-lactic acid therefore has the (5)-configuration. The (+)-acid 011) was obtained from the (-)-alcohol (I) without involving the asymmetric centre and this alcohol therefore has the (R)-conf&pration. 0 9 This (-)-alcohol [a] -0.82" has been con-verted into the (-)-diene (11) [ar -53-1' with a Brewster J.Amer. Chem. SOC.,1959 81 5475. Richards (Ann. Chim. Phys. 1910 21 323) obtained anhydrous (f)-2-t-butyl-lactic acid by sublimation and gave m.p. 141-142". Favorskaya(J. Gen. Chem. (U.S.S.R.) 1948,18,52) obtained a hemihydrate m.p. 141". Our (&)-acid crystallised as the hemihydrate which changes crystalline form to the anhydrous acid at 65" and has m.p. 99". Heating in vacuo gives anhydrous (&)-acid m.p. 99"; coalescence to give a clear liquid takes place only at 140". Prelog Helv. Chirn.Acta 1953 36 308; McKenzie J. 1905 87 1373. MAY 1962 1a3 thionyl chlorides by the method previously described? allylic rearrangements,* but is less stereospecific than We believe that the reaction proceeds principally by the SJ' mechanism. an SJ' rather than an S,2' mechanism (but cf.It is concluded that the (-)-diene (II) has the ref. 2) as experiments carried out in the presence of (3-configuration and the (+)-diene (11) therefore tributylaminee (which yields a soluble base hydro- has the (R)-configuration as predicted. chloride favouring the S,2' mechanism') give allenic chloride of lower activity. Apparently the SN2' We thank the Chemical Society for a grant for mechanism mainly gives double inversion with chemicals. propargyl-allene rearrangements as it does with (Received January 23rd 1962.) a Unpublished work by Evans Candor and Taylor-Smith. De Wolf and Young Chem. Rev. 1956,56 753. Stork and White J. Amer. Chem. SOC.,1956,78,4609. The Allraline Hydrolysis of 3-Acetoxy-5a,8aepidioxyergosta-3,6~-trkne By PETER BLADON SLEIGH and THOMAS (CHEMISTRY ROYALCOLLEGE AND TECHNOLOGY, DEPARTMENT OF SCIENCE GLASGOW) oxygenation1 of 3-acetoxyergosta-and 1597 cm.-l.The nuclear magnetic spectrum of PHOTOCHEMICAL 3,5,7,22-tetraene2 in the presence of eosin afforded the acetate contained a symmetrical quartet of peaks Inter alia the expected 3-acetoxy-5 a,8 a-epidioxy-due to the AB system of the C-6 (73.82) and C-7 ergosta-3,6,22-triene (I). On treatment with alkali (T 3-39) protons (J 11 c./sec.) together with a broad this epidioxide underwent saponification accom- unresolved peak due to the side-chain olefinic panied by a novel rearrangement to yield 4-hydroxy- protons (T4.72). The absence of a sharp singlet peak ergosta-4,6,8( 14),22-tetraen-3-one (11; R = H) (C-4) in the olefinic region together with the high [a]D + 733" (in CHCI,) Amax 262,370 mp (E 6600 positive rotation ([a]D + 624" in CHCl,) and the and 21,000) Vmax.(in CClJ 3400 (hydrogen-bonded ultraviolet spectrum excluded the alternative struc- OH) 1656 (hydrogen-bonded unsaturated ketone) ture (111) for the acetate [cf. ergosta-4,6,8(14),22- tetraen-3-one3]. The epidioxide (IV) derived from 3-acetoxyergosta- 3,5,7,9( 1 1),22-pentaene behaved analogously on treatment with alkali yielding 4-hydroxyergosta- ACO&I7'-''00 4,6,8(14),9(11),22-pentraen-3-one 0. The rearrangement can be envisaged as proceeding 0&7 OR through the stages illustrated. The authors thank Dr. J. C. D. Brand for the and 1600 cm.-l that gave an acetate (11; R = Ac) nuclear magnetic spectrum and acknowledge a Amax.248 357 mp (E 330 and 7100) vmrax.(in maintenance grant (to T.S.)from the Cross Trust KCI) 1773 (enol acetate) 168 1 (unsaturated ketone) (Received March 28th 1962.) Bladon J. 1955 2176. * Heilbron Kennedy Spring and Swain J. 1938 869. a Eh,J. 1954 468. PROCEEDINGS Nuclear-spin Coupling Constants and d3onding in Platinum Complexes By A. PIDCOCK and L. M. VENANZ~ R. E. RICHARDS (INDRGANIC CHEMISTRY SOUTH AND PHYSICAL LABORATORIES PARKSROAD,OXFORD) THE nuclear-spin coupling constants between plati- num and phosphorus nuclei have been measured in a number of square-planar platinum(I1) complexes (see Figure). The values of the extremely large coupling constants vary markedly with the structure of the complex and can be correlated with the types of bonding involved.The coupling constants were obtained from both the platinum and the phosphorus resonances measured in concentrated chloroform solutions of the complexes. The phosphorus resonance spectrum is a triplet; the central component arises from mole- cules containing platinum nuclei with zero spin and the two outer components arise from molecules con- taining the platinum-195 nucleus which has a spin quantum number of 6. The frequency separation of the outer lines is equal to the platinum-phosphorus coupling constant.l There is evidence that in compounds of the type [(R,P),PtX,] platinum-phosphorus d,-d bonding2 is stronger in the cis- than in the trans-isomer because in the latter the two phosphorus atoms (regarded as lying on the x axis of the molecule) can use only the d,,-and d,,-orbitals for n-bond formation while in the cis-isomer the dzy-,d,,- and d,,-orbitals are available for T-bonding.This difference is largest when the anionic ligands X have low rr-bonding capacity as is the case for chloride. Thus Chatt and Wilkins3 have found that the total bond energies of cis-[(R,P),PtCl,] ,(R = Et or Prn) are greater than in the trans-isomers by about 10 kcal. per mole. Since we find the coupling constant is about 1-5 times larger in cis- [(Bun3P),PtC1,] than in the trans-isomer it appears that the coupling constant is largely deter- mined by the strength of the rr-bond because the a-bond should be very similar in the two isomers.The importance of n-bonding is confirmed by com- paring cis-[(Bun,P),PtC12]with cis-[( (EtO),P},PtCl,]. The triethyl phosphite ligand containing the electro- negative ethoxy-group is expected to have a smaller a-bond donor power than the tri-n-butylphosphine group. However the acceptor properties of the phosphorus d-orbitals in triethyl phosphite should be stronger than in tri-n-butylphosphine. This is con- firmed by the increased ligand-field splitting ob- served in the visible-ultraviolet absorption spectrum of trans-[(MeO),P,piperidinePtCI,] than in trans- [Pr”,P,piperidinePtCIJ .* Also it appears that the cis-isomer is relatively more stable in the phosphite complex than in phosphine compounds since trans- [((EtO),P),PtCl,] is completely converted into the Jpt-P Kc./sec.2 2-31 -Ir0ns-I(Bun3P)2Pt Br,] 2.46 -trons-(B~”~P),PtCL,] (7) 3 3.27 -3.34 -3-51 -3.62 -3-81 -4 5 5.70 -~is-[{(EtO),P)iPtCt,] (5) 6 (Refs. in parentheses) cis-isomer in boiling chlor~form,~ whereas the trans- phosphine complexes are present to the extent of > 95% at equilibrium in benzene.3 In accordance with this we find the coupling constant of cis-[((EtO),P},PtCl,] to be > 1.5 times that of cis- [(Bun,P),PtC1,]. It is interesting that the coupling constants in Pople Bernstein and Schneider “High-resolution Nuclear Magnetic Resonance,” McGraw-Hill Book Co. Inc. 1959 Chapter 5. Chatt Duncanson and Venanzi J. 1955,4456; Craig Maccoll Nyholm Orgel and Sutton J.,1954 332.Chatt and Wilkins J. 1956 525; 1952,4300. Chatt Gamlen and Orgel J. 1959 1047. Gmelm “Handbuch der anorgankchen Chemie,” 8th edn. No. 68 Platinum (D) p. 351. Chatt Gamlen and Orgel J. 1958 486. ‘Chatt and Wilkins J. 1951 2532. Chatt and Venanzi J. 1955 3858. Chatt and Shaw Chern. and Ind. 1961 290. lo Chatt and Venanzi J. 1955 2787. MAY 1962 trans-[(Bun3P)(Amine)PtC1,] where amine = ethyl-amine diethylamine or pyridine are equal. The variation in amine basicity might well affect the a-bonding in the platinum-phosphorus linkage but the nitrogen cannot take part in r-bonding6 and so does not affect the coupling constant. Also since nitrogen does not form r-bonds of this type the coupling constant for the amine complexes is closer to that for cis-f@~n,P)~PtCl,] than for the trans-compound.We thank the Department of Scientific and In- dustrial Research for a maintenance grant (A.P.) and for grants in aid of apparatus and the Hydro- carbon Research Group of the Institute of Petroleum for financial assistance. (Received April 2nd 1962.) The Structure and Stereochemistryof Gibberellic Acid By FRANK A. I. SCOTT,G. A. SIM,and D. W. YOUNG MCCAPRA (DEPARTMENT THEUNIVERSITY, OF CHEMISTRY GLASGOW) To decide between the a-(I) and /%configuration (11) of the lactone ring of gibberellic a~idl-~ and to elucidate the stereochemistry of the gibberellic + allogibberic acid transformation we have made X-ray crystallographic and circular dichroism studies.Methyl bromogibberellate crystallises in the ortho- rhombic system space group P2,2,2, with four molecules of C2,H,,Br0 in a unit cell of dimensions Since the formation of the bromo-derivative (111) must involve the intervention of a mechanism similar to that demonstrated for the allogibberic -+ gibberic acid con~ersion,~ structure (IV) now follows for gib- berellic acid. The implication of this formulation which differs from previous proposal^*^^^^ will be discussed elsewhere; our results uphold the validity of the Hudson-Klyne rule1 for these y-lactones and ex- a = 10.74 b = 10.70 c = 16-64A. Three-dimen-sional intensity data were recorded on equi-inclina- tion Weissenberg photographs and were estimated visually 1716 independent values of F being obtained.The co-ordinates of the bromine atom were deter- mined unambiguously from Patterson syntheses and the remaining atoms (other than hydrogen) were located in three-dimensional electron-density distri- butions. The stereochemistry of this bromo-deriva- tive is shown in (In).The value of R is 21 % at present and further refinement of the atomic co-ordinates by the method of least squares is in progress. plain the ready opening of the lactone ring in the genesis of gibberellenic acid (V). That structure (IV) also represents the absolute configuration of gibber- ellic acid follows both from a previous assignment6 at C-2 and from the consideration of the following circular-dichroism results.Rotatory-dispersion measurements prove the absolute configurations of gibberic (VI) and epi- gibberic acid (the 4b-epimer of VI)?*' The formation of gibberic acid via (V) and allogibberic acid involves exchange of the 4b-hydrogen atom2 and rotatory-dispersion measurements do not provide unambiguous correlation between the gibberellic and the allogibberic-gibberic series.2 The circular di- Grove Quart. Rev. 1961 15 56; Cross Grove MacMillan Moffatt Mulholland Seaton and Sheppard Proc. Chem. Soc. 1959 302; Cross J. 1960 3022; Klyne Chem. and Ind. 1954 1198. Stork and Newman J. Amer. Chem. Soc. 1959,81 5518. Edwards Nicolson ApSimon and Whalley Chem. and Ind. 1960 624. Grove MacMillan Mulholland and Turner J. 1960 3049. Seta Takahashi Kitamura and Sumiki Bull.Agric. Chem. SOC.Japan 1958 22 429. 13 Masamune J. Amer. Chem. Soc. 1961 83 1515. 'Grove and Mulholland J. 1960,3007; Stork and Newman J. Amer. Chem. Soc. 1959,81,3 168. PROCEEDINGS chroisms (see Table) of compounds (III) (VI) and The trans-anttbackbone in gibberellic acid sug-the 4b-epimer of (VI) proves that the gibberellic -f gests that the methyl group originally present at allogibberic change is accompanied by inversion at C-10 (steroid numbering) is removed during the bio- position 4b. The dichroism curves of compounds (111) synthesis without prior migration to C-99 and that and the 4b-epimer of (VI) have almost identical cafestollO and its relatives provide the sole apparent maximal wavelengths whilst that of gibberic acid exceptions to the 9 I 0-anti-relationship among the (VI) shows not only a pronounced red shift but also tetracyclic diterpenes.ll an increased value for ~1 -El..We are indebted to Dr. B. A. Hems (Glaxo Circular dichroism maxima (dioxan solutions). Laboratories Ltd.) for a supply of gibberellic acid and Dr. S. Mitchell for help with measurement of Amax. €1-€r Amax. €1-€r Amax-Q-€r circular dichroism. Two of us (F.Mc. and D.W.Y. (‘‘I) 305 -3.3 315 -2.4 respectively) are grateful for stipends from Imperial 4b-Epimer 296 -3.2 of(~l) 297 -1.9 306 4.4 316 -1.5 Chemical Industries Limited and The Carnegie (Vi) 300 -3.5 309 -3.9 321 -2.5 Trust. (Received March 5th 1962.) See e.g. Velluz Angew Chem. 1961. 73 603. Birch Rickards Smith Harris and Whalley Tetrahedron 1959 7 241.lo Djerassi Cais and Mitscher J. Amer. Chem. Sac. 1959 81 2386; Finnegan and Djerassi ibid. 1960 82,4342. l1 Djerassi Quitt Mosettig Cambie Rutledge and Briggs J. Amer. Chem. SOC.,1961 83 3720; Wenkert and Chamberlam J. Amer. Chem. SOC.,1959 81 688. Homolytic Aromatic Substitution by Radicals Derived from Sulphonyl Halides W. CUMMINGS A. HUGHES, By P. J. BAIN,E. J. BLACKMAN SHEILA E. R. LYNCH E. B. MCCALL and R. J. ROBERTS (MONSANTO LIMITED RUABON DENBS.) CHEMICALS WREXHAM WEreport a new and convenient process for free- halide) of cuprous chloride ensures more rapid radical substitution of aromatic compounds based on reaction. the thermal homolysis of sulphonyl halides. Decom- It is suggested that the following reactions occur position of benzenesulphonyl chloride (1 mole) in during the substitution boiling biphenyl (15 moles) is complete in 4 hr.at 255” with evolution of nearly quantitative amounts of sulphur dioxide and hydrogen chloride. The mixed terphenyls isolated in 75 % yield show the high ortho- and meta-isomer content typical of free-radical attack ortho 47.0; meta 28.5; para 24.5 %. In boiling naphthalene complete decomposition requires 20 hr. and gives an 80 % yield of a 4 :1 mixture of 1-and 2-phenylnaphthalene. Aromatic substrates contain- ing groups susceptible to hydrogen abstraction by the substituting radical may give complex side-reaction and low yields but otherwise yields are high and the + HCL t R. process is of wide scope.Aromatic disulphonyl chlorides aromatic sulphonyl bromides and alkane- sulphonyl chlorides react similarly though yields may be low in the aliphatic case. Several metals and their salts exert a marked catalytic effect on the decomposition :incorporation Evidence for the formation of chlorine atoms has in the substrate of 0.1 mole% (based on sulphonyl been found in the displacement of bromine from Sulphonyl chloride Substrate Product M.p. Benzene-p-CeHdBr2 2,5-Di bromobiphenyl 40-42” Benzene-1,3,5-C6H3C1 2,4,6-Trichlorobiphenyl 59-61 Benzene-1,2,4,5-C6H,CI 2,3,5,6-Tetrachlorobiphenyl 78-79 Pentafluorobenzene- 1,3 5-C6H3Cl 2’,4’,6‘-Trichloro-2,3,4,5, &pen tafiuorobiphenyl 60-6 1 Benzene-rn-di-p-C6H4Br2 2,5,2” 5”-Tetra bromo-m- terp hen yI 134-1 35 Benzene-m-di-1,3,5-C,H3C13 2,4,6,2”,4”,6”-Hexachloro-rn-terpheny1 164-166 MAY1962 certain brominated substrates.The surprisingly clean nature of the reaction may be due to the generation in close proximity of the substituting species and the dehydrogenating C1- or .S02Cl radical. The following additional examples demonstrate the scope of the reaction. Toluene-p- p-nitro- benzene- and pyridine-3-sulphonyl chloride each gave in boiling biphenyl mixtures of three main components with the lowest-boiling predominating. Jsolation of the highest-melting component by frac- tional crystallisation gave respectively 4-methyl-p- terphenyl (m.p. 204-207 ”) 4-nitro-g-terphenyl (m.p. 205O) and 3-(3-biphenylyl)pyridine (m.p. 151-1 52 ”).For unambiguous substitution reactions 1,4-di- bromo- 1,3,5-trichloro- and 1,2,4,5-tetrachIoro-benzene were employed as substrates with the results given in the Table. Substitutions with the penta- fluorophenyl radical have not hitherto been described. The authors thank Mr. R. A. Lidgett for the gas-chromatographic analyses. (Received March 22nd 1962.) NEWS AND ANNOUNCEMENTS Election of New Fellows.-272 Candidates whose names were published in Proceedings for March have been elected to the Fellowship. Deaths.-We regret to announce the deaths of the following Dr. S. Azim (14.1.62) recently of Southampton University; Mr. J. J. V. Backes (8.2.62) Technical Director of Malgavita Ltd. Southall; Mr. R. B. Drew (31.3.62) formerly Chief Chemist British Glues and Chemicals Ltd.London; Professor A. Langseth (October 1961) of the Uni- versity of Copenhagen; Mu. R. O’F. Oakley (4.3.62) formerly of D.S.I.R. ; Mr. E. Russell (1 3.3.62) a Fellow for over 70 years; and Dr. E. W. Tapley (30.3.62) of Southgate. British Association for the Advancement of Science.-The Annual Meeting of the British Association for the Advancement of Science will be held in Manchester from August 29th to September 5th 1962. The Annual Meeting is the largest scientific gathering of its kind in the year and the only one which members of the general public can join on equal terms with scientists. It not only pro- vides a platform on which scientists can discuss their work with their colleagues in their own language and one on which scientists in separate but related fields can consider the “growing points” of science but also affords an unrivalled chance for the layman to learn something of the progress of science from the scientists concerned.The Annual Meeting is open to all who are interested in the progress of science and in its impact through its applications on society as a whole. Enquiries should be addressed to the British Associa- tion Office 3 Sanctuary Buildings Great Smith Street London S.W.1. Royal Society of Edinburgh.-The following have been elected Fellows of the Royal Society of Edin-burgh Dr. C. L. Hewett Dr. F. R. Smith and Dr. R. H. Thomson. The Royal Institute of Cbemistry.-Dr. R. E. Parker at present Lecturer in Organic Chemistry at the University of Southampton has been appointed Secretary and Registrar of the Royal Institute of Chemistry with effect from October lst 1962 in succession to Dr.H. J. T.Ellingham O.B.E. who will remain in the service of the Institute in a con- sultant capacity until the end of the year. Meldola Medals.-The Council of the Royal Institute of Chemistry with the concurrence of the Society of Maccabaeans has awarded Meldola Medals for 1961 to Dr. J. N. Murrell for his work in the field of theoretical chemistry with special reference to the interpretation of the electronic spectra of organic molecules and to Dr. R. 0.C. Norman for his work in the field of organic chem- istry with special reference to the application of modern methods of analysis to the elucidation of mechanisms of reaction or aromatic compounds.International Congresses etc.-An International Conference in Chemical Physics in the Onsager Reciprocal Relations will be held in Providence Rhode Island U.S.A. on June 12-14th 1962. Further enquiries should be addressed to Associate Professor John Ross Chemistry Department Brown University Providence 12 R.I. U.S.A. The Second International Congress of Radiation Research will be held in Harrogate Yorkshire on August 5-1 1 th 1962. Further enquiries should be addressed to the Secretary Dr. Alma Howard Mount Vernon Hospital Northwood Middlesex England. The Thirteenth Session of the International Com- mission for Uniform Methods of Sugar Analysis (ICUMSA) will be held in Hamburg Germany on August 26th-3 lst 1962.Further enquiries should be addressed to the Hon. Secretary Dr. D. Gross Tate and Lyle Research Laboratories Keston Kent England. The First International Congress on Chemical Machinery Engineering and Automation will be PROCEEDINGS held in Brno Czechoslovakia on September 3rd- Sth 1962. Further enquiries should be addressed to the Chairman Prof. Dr.Ing. Frantisek Brabec Central Council Czechoslovak Scientific and Tech- nical Society Siroka 5 Prague 1 Czechoslovakia. The Eighteenth Symposium on Molecular Struc- ture and Spectroscopy and the Third Assembly of the Triple Commission on Spectroscopy will be held in Columbus Ohio on June 10-14th 1963.Further enquiries should be addressed to Dr. Harald H. Nielsen Chairman c/o Department of Physics and Astronomy Ohio State University 174 West 18th Avenue Columbus 10 Ohio U.S.A. The Fifth International Congress on Clinical Chemistry will be held in Detroit Michigan on August 19th-23rd 1963. Further enquiries should be addressed to Dr. D. G. Remp Secretary Henry Ford Hospital Detroit 2 Michigan U.S.A. The Second International Fermentation Sympos- ium sponsored by the Society of Chemical Industry will be held in London on April 13-17th 1964. Further enquiries should be addressed to the Honorary Secretary Second International Fermenta- tion Symposium Society of Chemical Industry 14 Belgrave Square London W. 1. Personal.-Professor A.Albert Head of the Department of Medical Chemistry Institute of Advanced Studies Australian National University Canberra is spending six months study leave at the London School of Hygiene. Dr. V. C. Barry has been elected Treasurer of the Royal Irish Academy. Mr. H. A. Collinson has been awarded the British Institute of Management’s Wilson Medal for 1961. Mr. E. A. Cooke has retired from Imperial Chem- ical Industries Limited where he was Universities’ Liaison Officer. Responsibility for general contacts with the Universities will pass to Dr. M. A. T. Rogers Assistant Head of the Research and Develop- ment Department at the Head Office of I.C.I. Dr. Trevor I. Williams Editor of “Endeavour,” will assist him. Dr. J. W. Cornforth a member of the National Institute of Medical Research and Dr.G. J. Popjak Director of the Medical Research Council’s Experi- mental Radiopathology Research Unit are to be jointly in charge of a Chemical Enzymology Unit formed by the Royal Dutch/Shell Group. Dr. J. W. Cruickshank has been appointed to the newly established Joseph Black Chair of Chemistry at the University of Glasgow from September 1st. Dr. B. K. Davison has resigned his position with Hardman and Holden Limited and has been ap- pointed Chemical Development Officer Develop- ment and Research Department International Nickel Co. (Mond) Ltd. Dr. S. K. Deb has taken up the position of Assistant Research Officer in the Applied Physics Division of the National Research Council Ottawa Ontario Canada.Mr. F. P. Doyle has been elected to the Board of Beecham Research Laboratories Limited and has been appointed Research Director in succession to Dr. J. Farquharson who has relinquished the appoint- ment on medical advice but who is to act as Special Consultant directly responsible to the Research Director Beecham Group Limited. Mr. G. Dring has retired from Bakelite Ltd. Mr. A. A. Eldridge and Professor G. Ingle Finch have been elected Fellows of the Imperial College of Science and Technology. Dr. A. C. M. Finch has taken up a Research Fellowship at the University of Leicester. Mr. V. Gallafent has been elected President of the Royal Photographic Society. Sir Charles Goodeve has been awarded the Bessemer Gold Medal for 1962 by the Iron and Steel Institute.Dr. P. Gross Principal Scientist of the Fulmer Research Institute has been appointed to the Board of Directors. The Earl of Halsbury has joined the Board of the Distillers Co. Ltd. and has also been appointed a part-time member of the North Thames Gas Board. Mr. H. T. Howard has been appointed Deputy Director of the Department of Technical Education of New South Wales Sydney Australia. Dr. A. C.Hutchison has taken up a new position as Manager Chemical Sales and Technical Service Department Imperial Chemical Industries Limited Nobel Division Glasgow. Dr. G. D. Luveluck formerly of the Welsh College of Advanced Technology Cardiff has been ap-pointed Head of the Department of Chemistry Atlantic College St.Donat’s Glam. Dr. D. C. Martin has been designated as Executive Secretary of the Royal Society instead of Assistant Secretary in accordance with an amendment to the statutes of the Royal Society. Professor V. Prelog has been elected a Foreign Member of the Royal Society. NAY1962 189 FORTHCOMING SCIENTIFIC MEETING London Thursday June 7th at 7.30 p.m. The following papers will be presented :“Reaction of Anthracene with Free Radicals derived from 2,2,4-Trimethylpentane (Iso-octane),” by A. L. J. Beck-with. “Dielectric Studies of CarboxyIic Acid-Pyridine Complexes in Benzene,” by M. Davies and L. Sobczyk. “Thermodynamic and Electrochemical Characteristics of the Ionic Dissociation of Methyl-triethylammonium Iodide in Methylene Dichloride,” by P.H. Plesch and J. H. Beard. To be held in the Rooms of the Society at Burlington House W.l. (Abstracts of the papers can be obtained from the General Secretary.) APPLICATIONS FOR FELLOWSHIP (Fellows wishing to lodge objections to the election of these candidates should communicate with the Honorary Secretaries within ten days of the publication of this issue of Proceedings. Such objections will be treated as confidential. The forms of application are available in the Rooms of the Society for inspection by Fellows.) Allen Edward Arthur B.Sc. 15 Rampart Street, Shoeburyness Essex. Aneja Rajindra Ph.D. The Rockefeller Institute New York 21 N.Y. U.S.A. Bailey Denis M. A.B. Ph.D. Department of Chemistry, Stanford University Stanford Calif.U.S.A. Bale Maurice Sydney B.Sc. 79 Grove Road Windsor Berks. Barger Hugh Jackson Jr. B.S. Frick Laboratory, Princeton University Princeton N.J. U.S.A. Bellas Michael B.Sc. A.R.T.C.S. 30 Gladville Drive Cheadle Cheshire. Bloomer James Lawrence M.S. 59 Queen’s Gate, London S.W.7. Boorman Philip Michael B.Sc. 7 Musters Road West Bridgford Nottingham. Boucher Ernest Arthur B.Sc. The Coats Linley Green Wh itbourne Worcs. Bowerman Gerald Edwin Fergus. Begbrook House 13 Begbrook Lane Stapleton Bristol. Bradshaw Keith B.Sc. 90 Macclesfield Road Hazel Grove Stockport Cheshire. Brown Eric Joseph Douglas 7 Tnunpington Street Cambridge. Carty Robert P. B.S. Ph.D. Department of Biochem- istry State University of New York 450 Clarkson Avenue Brooklyn 3 N.Y.U.S.A. Casier Georges Polydore Jules. 36 Rinses Lydialaan Heverlee Belgium. Charlton Brian George. Icknield Way House A.E.R.E. Hanvel! Didcot Berks. Chatterjee Suprabhat M.Sc. D.Phil. 24 Anselm Terrace Brighton 35 Mass. U.S.A. Cheeseinan Trevor Percival B.Sc. Chemistry Depart- ment University of Auckland Auckland New Zealand. Cherry Peter Clive. Keble College Oxford. Cherry Winston Howard B.Sc. 18 Epping Street East Malvern S.E.5 Victoria Australia. Chittenden Gordon James Frederick. 6 Upper King Street,Leicester. Chiusoli Gian Paolo Dr.chem. Via Giovanetti 5, Novara Italy. Ciment David Martin B.Sc. 45 Green Walk Hendon London N.W.4. Clare Roy Allan. 42 Poppleton Road Leytonstone London E.11. Coates John Stuart B.Sc. 2408 Water Street Apt. E, Boulder Colorado U.S.A. Coffey Robert Stevenson Ph.D. 41 Kings Court Mount Pleasant St. Albans Herts. Cook Alan Frederick B.Sc. 224 Grasmere Avenue Wembley,Middlesex. Cragoe Edward J. Ph.D. Merck Sharp and Dohme Research Laboratories West Point Pennsylvania, U.S.A. Crossland William Alden B.Sc. 70 Avondale Road Bromley Kent. Dahill Robert Thomas Jr. M.S. 188 William Street Perth Amboy New Jersey U.S.A. Daly John M. M.S. Ph.D. Bellarmine College 2000 Norris Place Louisville 5 Kentucky USA. Dalzell Tom Ph.D. 15 Buckingham Place Clifton Bristol 8. Dankner Shmuel M.Sc. 22 Shoshanat Hacarmel Street Haifa Israel. Denton David Alan A.R.T.C.S. 32 Crescent Road Hale Cheshire.Dolfini Joseph Edward Ph.D. Box 108 Department of Chemistry Havemeyer Hall Columbia University, New York 27 N.Y. U.S.A. Ewart Hugh Alan B.S. Chemistry Department Univer- sity of Rochester. Rochester 20. N.Y.. U.S.A. Farbkr Leon M.S.’ 1040 Eastern Parkway Brooklyn 13, N.Y.. U.S.A. Flouret; George M.S. 1726 Moyt Street Madison, Wisconsin U.S.A. Fort Raymond C. Jr. B.S. Frick Chemical Laboratory Princeton University Princeton New Jersey U.S.A. Freeman Peter John B.A. University College Oxford. Freeman Raymond Keith. 59 Entry Hill Bath Somerset. Galvin James Phillip B.Sc. Department of Chemistry, University of Manchester Manchester 13. Gerrans Graeme Charles B.Sc. University Chemical Laboratory Lensfield Road Cambridge.Gillam Michael Sydney. Nursery View Brook Street Kidderminster Worcs. Graham Ian Frederick BSc. Chemistry Department University College of London Cower Street W.C.I. Grinstein Reuben Henry Ph.D. Department of Chem- istry The University Leicester. Halleux Andre Ph.D. European Research Associates 95 rue Gatti de Gamond Brussels 18 Belgium. Harrison Albert Keith. 8 York Road Grappenhall Warrington Lancs. Hartley David Ph.D. Research and Development Divisions Wyeth Laboratories Inc. Radnor Box 8299, Philadelphia Pa. U.S.A. Hartter Donald Ray B.S. Department of Chemistry, University of California Berkeley 4 Calif. U.S.A. Harwood Susan Elizabeth B.Sc. Royal Holloway College Englefield Green Surrey. 190 Hashimoto Tadashi B.Sc.Department of Chemistry, The University LRicester. Hawker Frederick John B.Sc. Chemistry and Biology Department Sunderland Technical College Sunder- land Co. Durham. Hever Keith Owen B.Sc. 480 East Rochester Way Sidcup Kent. Hobman Jack B.Sc. 5 Elmhurst Grove Knottingley Yorkshire. Home Ralph Albert M.S. Ph.D. 96 Chestnut Street Boston Mass. U.S.A. Horsfield Anthony Ph.D. The Research Laboratory Varian Ag. Klausstrasse 43 Zurich 8 Switzerland. Ikeda Den-ichi B.Pharm. Nishiawajicho 3-283 Higashiyodogawaku Osaka Japan. Jabalpunvala Kaizer E. Ph.D. Chemistry Office Boston University 675 Commonwealth Avenue. Boston 15. Mass. U1S.A. Jarman. Henrv Thomas. O.B.E.. M.A. “Brendon.” 182 Gilbert Roah Cambridge. ’ Jarvis James Adrian B.Sc.45 Poplar Avenue Edgbaston Birmingham 17. Johnson Cecil Barry M.Sc. Department of Chemistry, Victoria University of Wellington P.O. Box 196, Wellington New Zealand. Jonathan Neville Ph.D. Geophysics Corporation of America Bedford Mass. U.S.A. Jones Albert Leonard Ph.D. Department of Chemistry and Metallurgy Royal Military College of Science Shrivenham Swindon Wilts. Kojima Masaharu Ph.D. Department of Chemistry Imperial College of Science and Technology South Kensington S.W.7. Lablache Combier Alain. Laboratoire de Chimie Organique Institut de Chimie Strasbourg Bas Rhin France. Lanigan Peter Gerald B.Sc. 82 Archery Grove Woolston Southampton. Lapporte Syemour J. Ph.D. California Research Corp. Richmond Calif. U.S.A. Lathwood Eric B.Sc.3 West Drive Salford 6 Lancs. Lavin lhomas Patrick Brendan B.Sc. 26 Clareville Road Karolds Cross Dublin 6. Leadbetter Graham B.Sc. 102 Noyes Laboratory University of Illinois Urbana Illinois U.S.A. Lowry John Brian M.Sc. Department of Organic Chemistry University of New England Armidale N.S.W. Australia. Mackie William B.Sc. Chemistry Department Univer- sity of Edinburgh West Mains Road Edinburgh. Magistro Angelo J. B.S. Carnegie Institute of Tech-nology Pittsburgh 13 Pennsylvania U.S.A. Maynard Judith Ann B.Sc. Division of Organic Chem- istry C.S.I.R.O. Box 4331 Melbourne Australia. Middleton Bruce Stanley B.Sc. 73 Minora Road, Dalkeith Western Australia. Mills Stuart Dennett Ph.D. Duke University Durham North Carolina U.S.A.Mitchell Earl D. Jr. B.S. Kedzie Chemical Laboratory Michigan State University East Lansing Michigan U.S.A. Moelwyn-Hughes John Timothy M.Sc. 216 Hills Road Cambridge. Moffatt Vivian Alexander B.Sc. 70 Woburn Drive Hale Cheshire. Mok Kum Fun M.Sc. Chemistry Department Victoria University of Wellington Wellington New Zealand. PROCEEDINGS Nicholson Anne Leslie B.Sc. 24 Swan Road Harrogate Yorkshire. Noyes Richard Macy A.B. Ph.D. Department of Chemistry University of Oregon Eugene Oregon U.S.A. Ouchi Ken’ichi. 15 Thorndale Street South Hamilton Ontario Canada. Pardoe Grace Irene B.Sc. F.R.T.C. 4 Bury Hill Road Round’s Green Oldbury Birmingham. Patel Ramesh. Holbeinstrasse 29 Braunschweig, Germany. Piazza Guiseppe Dr.Chem.Via Balduino 15 Catania, Italy. Powell Harry Kipton James M.Sc. 43 Plunket Street Kelbum Wellington New Zealand. Raman Natesan KaIyana Ph.D. Department of Physical Chemistry Imperial College Imperial Institute Road s.w.7. Russell Charlotte Sananes Ph.D. 159-34 Riverside Drive West New York 32 N.Y. U.S.A. Ryan Peter Bernard B.Sc. 46 Topaz Street Roath Cardiff Glam. Scott William Bruce B.Sc. 4564 Watling Street South Burnaby 1 B.C. Canada. Simon Wilhelm Dr.Ing.Chem. Laboratory of Organic Chemistry Swiss Federal Institute of Technology, Universitatsstr. 6 Zurich 6 Switzerland. Slootmaekers Pierre Jozef dr.sc. Lab. Algemene Scheikunde Naamse straat 96 Leuven Belgium. Snyder Eugene I. Ph.D. 324 Chestnut Street Roselle Park New Jersey U.S.A.Stark James Roger. c/o Davidson 10 Moat Street, Edinburgh 1 1. Szymanski Chester D. Ph.D. 8 Pine Street Road No. 2, Bound Brook New Jersey U.S.A. Tao Rosaline Chuen Chi B.Pharm. Ph.C. M.P.S. Whiffen Laboratory Imperial College Imperial Institute Road London S.W.7. Tennant George Ph.D. Strathcona Club Bucksburn Aberdeen. Thomas Einvyn B.Sc. 37 Arthur Street Ammanford Carms. Thomas Michael Barrie. 57 George Lane Notton Nr. Wakefield Yorks. Thompson James Char1 ton. Christ’s College Oxford. Turner John Christopher Ph.D. 741 Johnson Street Kingston Ontario Canada. Ulery Harris E. B.A. 252 South Mentor Apt. 6 Pasadena Calif. U.S.A. Wat Edward K. W. B.A. 926 20th Avenue Honolulu 16 Hawaii. Watts Rodney Bernard. 16 Station Road Rraunton North Devon.Weisbach Jerry Arnold M.A. Ph.D. Smith Wine and French Laboratories 1500 Spring Garden Street, Philadelphia 1 Pa. U.S.A. Wender Irving Ph.D. United States Bureau of Mines 4800 Forbes Avenue Pittsburgh 13 Pa. U.S.A. Wheldon William Rowley. 25 The Parade Washington Co. Durham. Winter George M.Sc. Department of Inorganic Chem- istry The University of Melbourne Melbourne, Victoria Australia. Witz Pierre. Ecole Nationale Superieure de Chimie 2 Rue Goethe Strasbourg Bas-Rhin France. Wright John Richardson. 19 Wentworth Road Oxford. MAY1962 191 OBITUARY NOTICES HENRY VINCENT AIRD BRISCOE 1888-I 961 H. V. A. BRISCOE was born in London and attended the Westminster City School and the City of London School.In 1906 he won a Scholarship at the Royal College of Science which in the following year was incorporated as a constituent college of the Imperial College of Science and Technology. It numbered among its senior faculty members Tilden T. E. Thorpe Callendar Perry and Watts with all of whom the college course brought him into contact. After graduating with honours in chemistry he stayed on at the college and assisted Sir Edward Thorpe in revising Thorp’s Dictionary of Applied Chemistry a task which as those who have engaged in similar work will appreciate can hardly fail to broaden the scientific outlook and at the same time develop a flair for scientific writing. Briscoe’s first academic appointment was as Assistant Lecturer in the chemistry department of the College and his first scientific publication which appeared in the Society’s Transactions (1912) was a joint paper with P.W. Robertson on the migration of para-halogen atoms in phenols. It appears that this single taste of organic chemistry sufficed and from that point onwards he turned to inorganic chemistry as his main academic interest. Undoubted- ly this change was due in part to the fact that H. €3. Baker had succeeded Sir Edward Thorpe as Pro- fessor of Inorganic Chemistry. He brought with him to the college interest and experience in preparative inorganic chemistry and in the determination of atomic weights. Both of these fields were already part of the tradition of the college and against this background Briscoe’s change of interest is readi!y understood.It was a change which was later to benefit the college tremendously for it enabled the early tradition to be developed. British chemistry was also to benefit greatly for Briscoe helped to keep the subject alive through the lean years following the First War when organic and physical chemistry were in the ascendant and could well have ousted the other subject in our major schools of research. Briscoe’s first publication on atomic weights was made jointly with €3. F. V. Little in 1914. It described a determination of the atomic weight of vanadium based on the ratio VOC1,:Ag. The nephelometric end-point was employed. Shortly afterwards (1915) a second paper appeared in the Transactions this time published by Briscoe alone and describing the determination of the atomic weight of tin based on the ratio SnC1,:Ag.These two papers in which fortunately the experimental work is described in considerable detail are models of fine experimenta1 research. The final conclusion that “the atomic weight finally deduced Sn = 118.70 would seem to be worthy of considerable confidence” is also notable for in spite of the disarming modesty of the claim this is still the accepted value. This work was sub- mitted for the degree of Doctor of Science in the University of London. The war years 1914-1 918 found Briscoe invoIved in a number of projects related to the war effort. He gave up his academic post in 1916 though he visited the college regularly to lecture on engineering chem- istry and also took charge of the Department of Organic Chemistry at the Sir John Cass College.He was also active in the design and operation of a factory for the manufacture of thorium nitrate and rare-earth materials. This period brought him into close contact with a number of industries and must have given plenty of scope for his inventiveness and interest in machines. They illustrate too how readily and effectiveIy a man with a rigorous training in scientific method can adapt himself to the require- ments and way of thinking of industry. This was true of Briscoe throughout his life. In 1921 Briscoe was appointed Professor of Inorganic and Physical Chemistry at Armstrong College (now King’s College) Newcastle and became Head of the Chemistry Department four years later in succession to the late Sir Norman Howorth.He remained at Newcastle until 1932 when he succeeded H. B. Baker as Professor of Inorganic Chemistry at the Royal College of Science. In 1947 on the retire- ment of J. C. Philip he became also Director of the Laboratories of Inorganic and Physical Chemistry. The years at Newcastle were particularly fruitful and he attracted a group of colleagues and co-workers with whom he collaborated in a large number of important research projects. Mention must first be made of the continuation of the determination of atomic weights. The first publication with P. L. Robinson was a redetermination of the atomic weight of bromine.The objective was to establish if any separation of the bromine isotopes could be brought about in the prolonged fractional crystallisa- tion of ammonium bromide. The answer was in the negative but the final value agreed with that accepted at the time. The atomic weight of boron was next redetermined by Briscoe and Robinson. Here again the underlying problem was not simply a redetermination of the atomic weight though the experiments lacked none of the elegance and precision of such work but a study of whether there was any variation in the iso- tope abundance in boron from different sources. The determinations were made by means of the BCl :Ag ratio and significant variations were ob- served. Thus boron from California gave a value of 10.840 a sample from Tuscany 10.824 and one from Asia Minor 10.820.The authors were careful to point out that a partial isotope separation might have occurred in the numerous fractional distilla- tions involved in their purification procedures. With this point in mind novel procedures were examined in attempts to clarify the position. These included the acid titration of fused borax prepared after fractional crystallisation of boric acid from different sources. Here the variable loss of sodium oxide during the fusion process was recognised as a source of error which was bound to vitiate any conclusions. A second method was the measurement of the density of boric oxide glass by flotation in mixtures of penta- chloroethane and trimethylene dibromide.These results at first showed variations similar to thcse shown by direct atomic weight determinations but in a later paper the significance of these results was minimised. Variations in the density of borcn tri- chloride were also studied by a novel flotation method. In a final chemical paper on atomic weights (1931) Briscoe Kikuchi and Peel determined the atomic weight of thallium from the ratio TICl:Ag obtaining a value of 204.34 i-0.015 compared with Honigschmidt's value of 204.39 j~0.012. The Newcastle period led to a number of publica-tions which were largely physicochemical in charac- ter. It is perhaps fair to comment that these do not reflect any deep interest in theoretical physical chem- istry on Briscoe's part.He himself would have been the first to disclaim such an interest. His studies did however touch on a number of interesting points and above all they involved elegant and often difficult experimental work. Instances of this sort are work on the catalytic dissociation of carbon monoxide to carbon and carbon dioxide on mag- nesium oxide and alumina at temperatures below 300" studies of the heats of mixing of organic liquids measurements of the dielectric constants of organic liquids and their mixtures cryoscopic measurements on such mixtures phase-transition studies and a detailed study of the hydrolysis of alkaline-earth halides and other salts by low-pressure steam at 400-900". The publications on preparative inorganic chem- istry from Newcastle fall under two headings.The fist embraces work on selenophen which was pre- pared in moderate yield from acetylene and selenium at 400". A number of its reactions were studied and interesting mercury-containing derivatives were pre- pared. The new compound carbon sulphide-selenide PROCEEDINGS was also made and here again reactions were studied in some detail. The second group of papers was on the chemistry of rhenium and its compounds. In this research and indeed in much else that was done at Newcastle Briscoe was very closely associated with P. L. Robinson. It is no exaggeration to say that a substantial part of our present knowledge of rhenium compounds starts from the work of the Newcastle school. It was done moreover at a time when rhenium was much less available than it is now.It included a study of the reduction of potassium per- rhenate leading to isolation of the black oxide Re0,,2H20 the study of a series of new perrhenates the characterisation of new rhenium sulphides and selenides and the isolation of new halogeno-rhenates halides and oxyhalides. He was also closely associated at this time with the work of the Northern Coke Research Committee and was a joint author in a number of publications on the physical properties of coke and on methods of testing and analysis. Briscoe's return to Imperial College coincided with the first demonstration by Urey that the partial enrichment of water in its heavy isotope was possible. This topic was taken up with zest and a number of publications with various collabcrators appeared over the next 20 years.The first of these were con- cerned with the abundance of deuterium in a wide range of water from different mineral vegetable and animal sources. The assay was done by precision density determinations based on measurement of the temperature at which a silica float was stationary in the sample under examination. Small variations in the abundance of deuterium were established and it was pointed out that these could be accounted for by the operation of such physical processes as selective evaporation or diffusion. Later several fully deuter- ated compounds were prepared and characterised. The observations were also extended to include kinetic studies of deuterium exchange with ammine complexes and with glutaconic acid in the presence of alkali.Isotope exchange work was also extended to studies of oxygen exchange in water enriched with l80 with a variety of oxyanions and also in one publication with zinc oxide the isotope-enriched material being obtained from a distillation unit operated in the department. Mention must also be made of a study of the evaporation of water into dry air through unimolecular films of various types and of the effect of ageing on such films. Finally Briscoe had two other research interests which though apparently not related to the main trends of his scientific work resulted in nevertheless major contributions. The first was the study of industrial dusts responsible for silicosis.His contribu-tion which formed part of a wide interest in micro- chemical techniques was the development of novel sampling techniques based on the use of porous MAY1962 filters made of volatilisable organic solids such as salicylic acid and naphthalene and also the detailed study of the alkalinity produced by injurious dusts in various media. He was awarded the Consolidated Goldfields of South Africa Medal by the Institution of Mining and Metallurgy in 1938 for his contribu-tion to this field. The second interest was the use of inert inorganic dusts in killing weevils in grain and in coping with similar problems. This was a war-time activity and it was carried through with character- istic thoroughness and success.Briscoe had many activities apart from his purely scientific work. He was associated with the work of the Paint Research Station from its earliest days and served as President of the Research Association of British Paint Colour and Varnish Manufacturers besides being very active in other capacities both in the work of the Association and in other facets of the paint industry. During the 1939-1945 war he gave his services in dealing with many scientific problems associated with the work of the Services and Government Departments. At the same time living for the most part on the College premises he kept teaching and research going under unusually difficult conditions. He rendered devoted service also to the Royal Institute of Chemistry serving for 16 years as a member of Council for 11 of which he was Vice-president.He served too on many of the Institute’s committees and was for many years Chair- man of the sub-committee for special examinations. He was greatly interested in students and seeing him together with them one felt that to an unusual degree and even in his later years he was able to see things from their point of view. He served as a member of the Council of the Society of Chemical Industry and was an Honorary Member of the Coke Oven Manufacturers Associa- tion as well as being closely associated with the research conducted by that body. He served for many years on the Council of the Building Research Station and was its representative on the Architeo tural Council for the Festival of Britain.He was also a Founder Fellow of the Institute of Fuel. He was also for a short time an Honorary Secretary of the Chemical Society. Retirement from the Chair at Imperial College in 1954 brought relief from academic duties but he sought none from his many other activities which also included a wide range of work as an inde-pendent consultant. He continued as treasurer of the Association of University Teachers serving in this capacity for fifteen years and became Chairman of the Editorial Board responsible for revising Mellor’s Comprehensive Treatise of Inorganic and Theoretical Chemistry a task comparable in magnitude with his early work on Thorpe’s Dictionary. He was also right to the end an active member of the I.U.P.A.C.Commission on Atomic Weights. That an active life should have ended with so much to do and so much well done is probably what Briscoe himself would have wished. His home life was like his scientific life busy and full of harmony. He married Rebecca Kirkwood Stevenson in 1915. She and their son and daughter both of whom are members of the medical profession survive him. They share with many friends throughout the scientific world the loss of one who will be remem- bered not only for his contribution to chemistry but also for his fine personal qualities. H. J. EMELBUS. JOSEPH KENYON 1885-1961 JOSEPH KENYON was born in Blackburn Lancashire on April Sth 1885. His father Lawrence Kenyon later had six other children.Joseph’s schooling was fairly normal for those days he attended the Primary School of St. Barnabas in Blackburn from 1890 to 1897 and the Secondary Higher Grade School in the same town for the next two years. He then was a laboratory assistant in what later became the Municipal Technical College Blackburn. Here he attended evening classes in chemistry (first under Dr. Conrad Gerland and then under Dr. R. H. Pickard) and in physics mathematics Latin and shorthand. In 1903 he passed London Matriculation in the First Class and in the following year took the London Intermediate in Science. In 1905 Kenyon became private assistant to Pickard in his capacity as Corporation Chemist and consultant to some cotton mills and in 1906 was appointed Assistant Lecturer and Demonstrator at Blackburn Technical College attaining a full Lecturership in the following year.Whilst studying for the London External B.Sc. Chemistry Honours Degree which he took in 1907 he started some research publishing three papers with Pickard two of them on “The Chemistry of Oxygen Compounds” and the other a classic with a permanent place in chemistry on “The Resolution of sec. Octyl Alcohol.” Kenyon then began the experimental work which he continued for eight years and the results of which he and Pickard published under the title “Investigations on the Dependence of Rotatory Power on Chemical Constitution.” This work had to be temporarily stopped because of World War I Kenyon going to the University of Leeds in February PROCEEDINGS as a research chemist to the Medical Research Council.Here he worked with J. B. Cohen and H. D. Dakin in attempts to find an antidote for “gas gangrene”. This led to the use of chloramine-T. Meanwhile in 1914 Kenyon had been admitted to the London D.Sc. In March 1916 W. H. Perkin jun. invited him to join the group at Oxford working on dyestuff inter- mediates dyestuffs photographic developers and other subjects Kenyon becoming a research chemist to British Dyestuffs Corporation. Part of his time he spent at the firm’s Huddersfield works trying out semi-manufacturing-scale processes. In 1920 how- ever he was able to return to his stereochemical researches as he was appointed Head of the Depart- ment of Chemistry at Battersea Polytechnic.He held this post until he reached the retiring age in 1950. Kenyon soon attracted good undergraduates and postgraduates for he was a clear and careful lecturer and above all was manifestly interested in experimental work in which he was very skilled and which he therefore enjoyed. He was fortunately able to launch and keep going his research school without being greatly hampered by the paraphernalia of modern administrative methods. He wrote his own Ietters in a clear bold hand and his signature did not require explaining in typescript. He loved his laboratory and gained the respect and collaboration of his staff and students by the example he set. The school became known all over the world the published research was of a quality (as well as of quantity) rivalling that of many more elaborate establishments.Pickard and Kenyon published (with H. Hunter) one more part of the Rotatory Power and Constitu- tion series in 1923 but thereafter whilst for a time Kenyon continued to use the same general title the scope of the researches widened a great deal Part XXIX being an account of the optical resolution of a sulphoxide which followed the resolution of a sulphinic ester by Phillips working in Kenyon’s laboratory. These very striking results greatly illu- minated the problem of the valencies of sulphur. At that time the new work pointed to S+O rather than S=O for the sulphoxide link this satisfying the then authoritative octet rule.In a brief survey of the work of Kenyon and his school only a few of the more important things can be mentioned. He had many collaborators of whom it is I hope not invidious to give special mention to H. Phillips F. Bell M. P. Balfe and C. L. Arcus. In 1926 with Bell he put forward one of the earliest explanations of the observed optical activity of certain substituted diphenic acids coining the useful term “obstacle group” as describing the effects postulated. Chemists owe much to the Kenyon school for their legacy of sound methods for the optical resolu- tion of different types of compounds and of alcohols in particular. There are many invaluable data for which one is glad to have his published verification.Interesting work was done by Kenyon and Phillips in the early 1920’s on the Walden inversion when it was still a baffling problem. One of the chief things needed was to pin-point the stage at which inversion took place. Kenyon and Phillips made many contri- butions in this direction including the following It was shown that the condensation of (+)-benzylmethylcarbinol with toluene-p-sulphonyl chloride in presence of pyridine gave the (+)-sulphonate and since this would appear not to involve carbon-oxygen bond-breaking it was thought that no configurational change had occurred. Formation of the (+)-ethyl ether of the alcohol from the potassium derivative of the latter and ethyl bromide similarly involved no configurational change because the C-0 bond was not broken so that apparently the ether and the (+)-alcohol have the same configuration.The (+)-sulphonate reacted with ethyl alcohol in presence of potassium car-bonate to give a (-)-ether the configuration of which must be the opposite of that of the original (+)-alcohol. On the other hand the potassium derivative of the latter gives the (+)-ether when it reacts with ethyl toluene-p-sulphonate. A similar set of conclusions was published in 1929 by Houssa Kenyon and Phillips. Changes involving optically active octan-2-01 are shown in Scheme A; these provided probable proof that the only stage at which inversion was likely was that in which a sulphonyloxy- was replaced by an acetoxy-group since this was the only change in which the bond between the asymmetric carbon atom and the oxygen was broken.It was also assumed that the change brought about by the action of lithium chloride was an inversion so that the (+)-alcohol and the MAY1962 195 (+)-chloride must have the same configuration. Kenyon’s interest in the use of optically active compounds in the study of the mechanism of organic reactions led him at one stage to examine the hydro- lysis of carboxylic esters particularly as regards the a1 ternative processes of acyl-oxygen and alkyl-oxygen fission. One example taken was the alkaline hydrolysis of (+)-c~.:y-dimethylallyl hydrogen phtha- late. When excess of 5~-sodium hydroxide was used the resulting ay-dimethylallyl alcohol was almost optically pure but with only a slight excess of dilute alkali the alcohol was obtained in a largely racemised form.This he recognised as due to acyl-oxygen fission with the strong alkali and alkyl-oxygen fission with the dilute alkali the second process permitting the intermediate mesomeric ion (A) with consequent loss of the asymmetry. + Me-CH.CH.CH-Me (A) A dramatic practical illustration of the conse-quences of alkyl-oxygen fission was given by Kenyon and his associates with (+)-p-methoxybenzhydryl hydrogen phthalate. It was observed that a clear solution of this ester in an equivalent of cold 0-1 S~-aqueous sodium hydroxide begins to become milky in a few minutes whilst overnight an almost quantitative separation of the neutral phthalate takes place expressed originally as The extension of the work on ester hydrolysis was admirably surveyed in Quarterly Reviews (1 955 9 203) by Davies and Kenyon.The ability of group R in an ester RO-CO-R’ to become a carbonium ion was shown by many examples to be promoted by substituents with high powers of electron-release for example the p-methoxy-group in the above case. Fundamental work was done by Kenyon in connexion with the Beckmann rearrangement of ketoximes and the Hofmann Curtius Lossen and Schmidt reactions ; convincing evidence was pro- duced that in all of these in which the characteristic common factor is the migration of a group the migrating group cannot become kinetically free since its movement causes no loss of asymmetry.All five reactions were started with (+)-hydratropic acid which had been shown to have the same con- figuration as (-)-I -phenylethylamine the final product of each of the changes. During his tenure of the Headship of the Depart- ment of Chemistry at Battersea Kenyon played his part as a member of the University Board of Studies in Chemistry at the meetings of which his sound knowledge of the subject made him very helpful. When he reached the compulsory age for retirement in 1950 he was reappointed to the Board as a so- called Other Person an honour extended to few men at retirement. He was a very good examiner and gave the University great service on both the Internal and the External side. Kenyon acted as a Visiting Professor at the University of Alexandria during the winters of 1950-1951 and 1951-1952 and he became an acting Professor in the University of Kansas in 19561955.Until his death he otherwise was back at Battersea. helping with the supervision of postgraduate research. He never lost his delight in the laboratory and its doings. Kenyon joined The Chemical Society in 1908 and se6ed for three periods as a Member of Council and for two periods as a Vice-president. He became an Associate of the Royal Institute of Chemistry in 1908 and a Fellow in 1911. His election as a Fellow of the Royal Society in 1936 gave great pleasure throughout the chemical world. In 1917 Kenyon was married to Winifride Agnes Younger; they had one daughter. He died in London on Sunday November 12th 1961.His widow and (married) daughter survive him. He had literally spent his long life in the laboratory in which and outside which he had made innumerable friends. E. E. TURNER. RAFAT MIRZA 1926-1 961 RAFATMIRZA was born on August 5th 1926 at Hyderabad. His quite unexpected death after a very short illness on his 35th birthday was a great shock to his wide circle of friends and acquaintances. Mirza began his education at the Hyderabad State School of Madrasa-I-Aliya and subsequently went to Madras University in 1942. He obtained 1st class Honours in Chemistry in 1946 and afterwards went to the California Institute of Technology where he obtained his M.S. in the summer of 1949. In the autumn of that year he joined St.Catherine’s Society Oxford and began work on the reduction of hetero-cyclic substances under the supervision of Professor Sir Robert Robinson. He obtained his D.Phi1. in November 1951 and returned to India where he worked at the Central Laboratories for Scientific and Industrial Research in Hyderabad for about a year. He became a Fellow of the Chemical Society in 1952. After about six months with Professor V. Prelog in Zurich he crossed the Atlantic again to take up a Research Fellowship in Harvard with Professor R. B. Woodward. He spent a further year in America as a post-doctoral fellow in Wayne University Detroit with Professor C. Djerassi and then came back to England in 1955 to join Imperial Chemical Industries Limited Dyestuffs Division at Manchester as a research chemist.In the autumn of 1960 he moved to the I.C.I. Akers Research Laboratories Welwyn to work in the Biophysics section. Much of Mirza’s published research concerned the lithium aluminium hydride reduction of heterocyclic compounds and followed from his work with Sir Robert Robinson when he converted kaempferol to pelargonidin and hydrastine to berberine. Similar reductions were the subject of his five papers from the Central Research Laboratories. His work in Switzerland contributed to a paper on corynantheine while in Harvard he helped to synthaise a degrada- tion product of cevine and some special types of benzylisoquinolines. “Raf,” as he was usually called was a man of many parts and interests and always threw his whole energy with great devotion and intensity into what- ever he was doing.Before coming to England he became an expert horse rider and played much polo. He loved doing things with his hands and this con-tributed to his mastery of experimental organic chemistry. As a gardener he was both enthusiastic and successful and reared many types of unusual plants. Photography was another of his hobbies. The remarkable prints he made aIways attracted atten- tion in competitions and a number were hung in international exhibitions. While in Detroit Mirza took up flying and subsequently aero-modelling. In recent years his interest in walking and climbing developed and he spent many happy weekends in Wales which were characterised by his good com- radeship and excellent cooking.He married in 1956 and his wife survives him; there are no children. Mirza was a very cheerful and likeable man with unusual ideas. He brought pleasure and happiness to many and his early passing will be greatly regretted by his many friends. R. M. ACHESON. ADDITIONS TO THE LIBRARY Lavoisier-The crucial year background and origin of his first experiments on combustion in 1772. H. Guerlac. Pp. 240. Cornell U.P. Ithaca New York. 1961. Molecular sieves. C. K. Hersh. Pp. 129. Reinhold. New York. 1961. Distillation principles and design procedures. P. J. Hengstebeck. Pp. 365. Reinhold. New York. 1961. Molecular structure and the properties of liquid crystals.G. W. Gray. Pp. 314. Academic Press. London. 1962. Experimental thermochemistry prepared under the auspices of the International Union of Pure and Applied Chemistry Subcommission on Experimental Thermo-chemistry. Eaited by H. A. Skinner. Vol. 2. Pp. 457. Interscience Publishers Tnc. New York. 1962. Chromatography. Edited by E. Heftmann. Pp. 753. Reinhold. New York. 1961. Microdiffusion analysis and volumetric error. E. J. Conway. 5th edn. Pp. 467. Crosby Lockwood. London. 1962. Qualitative elemental analysis. E. H. Swift and W. P. Schaefer. Pp. 469. Freeman. San Francisco. 1962. (Presented by the publisher.) The analysis of titanium zirconium and their alloys. W. T. Elwell and D. F. Wood. Pp. 198. John Wiley and Sons. London.1961. Electrochemical reactions :the electrochemical methods of analysis. G. Chariot J. Badoz-Lambling and B. Tremillon. Pp. 376. Elsevier. Amsterdam. 1962. (Pre-sented by the publisher.) The electrochemistry of semiconductors. Edited by P.J. Holmes. Pp.396. Academic Press. London. 1962. Iodide metals and metal iodides. R. F. Rolsten. Pp. 441. John Wiley and Sons. New York. 1961. Oxidation of metals and alloys. 0. Kubaschewki and B. E. Hopkins. 2nd edn. Pp. 319. Butterworths. London. 1962. Block and graft copolymers. R. J. Ceresa. Pp. 196. Butterworths. London. 1962. The mechanism of action of water-soluble vitamins. Edited by A. V. S. de Reuck and M. O’Connor. (CIBA Foundation Study Group No. 11.) Pp. 121. Churchill. London. 1961. Biological alkylating agents fundamental chemistry and the design of compounds for selective toxicity W.C.J. Ross. Pp.232. Butterworths. London. 1962. Inert atmospheres in the chemical metallurgical and atomic energy industries. P. A. F. White and S. E.Srnith. Pp. 235. Butterworths. London. 1962. A problem in chemical engineering design the manu- facture of acetic anhydride. G. V. Jeffreys. Pp. 134. Institution of Chemical Engineers. London. 1961. The chemistry and technology of leather. Edited by F. O’Flaherty W. T. Roddy and R. M. Lollar. Vol. 3. Pp. 518. Reinhold. New York. 1962. The enzymes of lipid metabolism proceedings of the Sixth International Conference on the Biochemistry of Lipids held at Marseilles 1960. Edited by P. Desnuelle.Pp. 308. Pergamon Press. Oxford. 1961. Advances in the chemistry of the co-ordination com- pounds. Edited by S. Kirschnx proceedings of the Sixth International Conference on Co-ordination Chem- istry held at Wayne State University Detroit Michigan 1961. Pp. 682. Macmillan. New York. 1961. NEW JOURNALS Leicester Chemical Review from 1962 No. 1. Fortschritte der Arzneimittelforschung from 1959 1.
ISSN:0369-8718
DOI:10.1039/PS9620000165
出版商:RSC
年代:1962
数据来源: RSC
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