EDMINSON AND HILDITCH: OPTICAL ACTIVITY. PART IV. 223XXV. -The B f e c t of Contiguous Uksatui-ated Groupson Opticcd Activity. Purt IV. CoiajugutedSystems containiug more thun Two Umcu%ratedG7-oups.By SYDNEY ROBERT EDMINSON and THOMAS PERCY HILDITCIZ.IN the course of work on the effect of two adjacent unsaturated radicleson molecular rotatory power, some of which has already been publishedin earlier parts of this series, it has been established that a pronounce224 EDMINSON AND HILDITCH : THE EFFECT OF CONTIGUOUSincrease of optical activity invariably accompanies the conjunction oftwo such groups. At the same time, it has frequently been noticedthat when a third group, possessing marked residual afinity, happenst o occur in close proximity to the studied systems, the increase inrotatory power is not always maintained, and, indeed, is sometimesmarkedly lessened.This may be instanced from the rnenthyl esters of piperic and sorbicacids, recently studied by one of us (Trans., 1909, 95, 1570), of whichwe reproduce here the molecular rotatory powers and correspondingdifferences from the " normal value " of a menthyl ester (a quantitythe approximate estimation of which has already been explained, Zoc. cit.,p.1571):[MI:. Difference.CGH5'CH:CH*CH:CH*CO,'C,nH,S ......... - 188'8 +28'3CH3*CH:CH*CH:CH'C0,*C,oH,g ........ - 221 -3 + 56.7The brucine salts of these acids, on the other hand, show a'' difference " of + 218-8O for the piperate, and + 119.5' for the sorbate,under identical polarimetric conditions.Again, the brucine salts of anthranilic and salicylic acids and theiracylated derivatives give evidence of similar irregularities (Trans.,1908, 93, 1388):[MID.Difference.Brucine benzoate .................... - 131'1 +118'4 .. ant hranilato .................. - 47.8 + 201 -7 .. acetylanthranilate ......... I- 29'8 +279-3 .. benzoylanthranilate.. ....... + 156 '2 + 405'7 .. benzoate ..................... - 131'1 + 118% .. salicylate ..................... + 75 '5 + 325.0 .. acetylsalicylate. .............. -I- 86.7 $. 336.2 .. benzoylsalicylate ............ +o-0 -I- 249-5Since mono-aryl esters of camphoric acid and camphor-P-sulphonicacid can be readily prepared and obtained pure, and since phenolicsubstances containing as many as five adjacent unsaturated groupsare also easily obtainable, we thought it might prove interesting toexamine as extended a series as possible of these derivatives.DiE-culties appeared, however, in the case of the more complicated phenolsused, chiefly owing to the decreasing facility of reaction shown onascending the series, and to the anticipated fact that the higher esters,although not so strongly coloured as their parent phenols, began to besufficiently dark yellow to interfere with polarimetric accuracy.We have endeavoured to arrive a t a "normal value" for themolecular rotatory power of acid esters of camphoric acid and ofcamphor-/I-sulphonic esters, in accordance with the usual rule(Tschngaeff, Ber., 1898, 31, 360; Walden, Ber., 1905, 38, 355), byexamining the methyl, ethyl, sz-propyl, and n-butyl esters of the twoacids.I n the case of camphor-P-sulphonic acid, we did not succeeUNSATURATED GROUPS ON OPTICAL ACTIVLTY. PART IV. 225in obtaining the propyl and butyl compounds in the pure state, andwe have therefore used the molecular rotatory power of the ethylester as a basis of comparison, since it is well known that the firstmember of the series is almost always irregular.Wc will return to a discmsion of the polarimetric results aftergiving some account of the compounds studied.EXPERIMENTAL.The alkyl hydrogen camphorates were prepared according toJ. Walker's directions (Trans., 1892, 61, 1088) ; a quantity of sodiumbeing dissolved in excess of the respective alcohol, the equivalentamount of camphoric anhydride was added, and the mixture boiledfor half an hour.The ester was then readilyisolated from the sodiumsalt formed.Eriihl (fie?.., 1891, 24, 3409) has observed that ethyl hydrogencamphorate tends to decompose, on being distilled in a vacuum, intothe diethyl ester and camphoric anhydride. We invariably foundtraces of anhydride in the distillate (under a pressure of 20 raw.)from either the ethyl, n-propyl, or n-butyl hydrogen esters, andultimately we purified them by extracting the ethereal solution of thecrude product with aqueous sodium hydrogen camphorate. Thisextract was cooled to Oo, acidified with a slight excess of mineral acid,and extracted again with ether. The dried ethereal extract wasfiltered, the ether removed by distillation, and the residue heated onthe water-bath in a vacuum for two hours.No appreciable decom-position thus took place, and the ethyl hydrogen ester so obtainedshowed a slightly higher rotatiori than that hitherto observed.We should mention that Walker (Zoc. cit.) has proved that in theaction of sodium alkyloxides on camphoric anhydride no allo-estersare formed.Met?uJ ?bytIvoge?c, carnplhoncte, CO, H C,H,,* CO,Rlle. - Colourlessneedles, m. p. 77':0.1046 gave 0,2373 CO, and 0.0813 H20.h'thyl lqdroyeu cant,phorcde, C0,H*C,H,4*C0,Et.--A colourless,0.1004 gave 0.2344 CO, and 0.0788 H20.n-Propyl hyd?.ogerc, ccmphorute, C O , H * C , H , * * C Q , * C ~ ~ ~ - ~ colour-Ob1O40 gave 0.2456 GO, and 0*0816 H,O.VOL.XCVII. QC = 6 1.87 ; H a8.64.C,,H,,04 requires C: = 61 *ci3 ; €1 = S.41 per cent.viscous oil :C! = 63.66 ; lI = 8-75!.C1,H2,,O, requires C = 63.1 7 ; H = 8.77 per centless, viscous oil :C: = 64.40 ; H = 9-04.C13H2204 requires c! = 64-46 ; H = 9.09 per cent226 EDMINSON AND HILDITCH : THE EFFECT OF CONl'lGUOUSn-Butyl hydrogen camphorate, CO,H*C,€€l,*CO,* C,H,. -A colourlessoil, much more limpid than the two preceding :0,1866 gave 0.4525 CO, and 0,1516 H,O.C,,H,,O, requires C: = 65.63 ; HThe alkylcamphor-P-sulphonates were obtained by heating equi-valent amounts of sodium alkyloxide and camphor-P-sulphonyl chloridein the respective alcohols for a short time. The product was mixedwith ice-water, and, when it had completely solidified, i t was collectedand recrystallised from aqueous methyl alcohol,Methyl camp?ior-p-suZphonafe, C,,H,,O*SO,Me.-Sof t, white needles,melting at 61O :0.1041 gave 0.8046 CO, and 0,0664 H,O.0,1630 ,, 0,1524 BaSO,.S= 12-83.Zthy! camphor-p-suZphonale, C,,H,,O*SO,Et.-Wax-like plates,0.1064 gave 0.2156 00, and 0.0750 H20.The n-propyl and n-butyl esters mere not obtained solid, either bycrystallisation from a number of solvents or on standing in avacuum desiccator for several weeks, and they were therefore notexamined.The unsaturated compounds studied may be divided into thosederived from phenol (0-hydroxybenzylidene-acetone and -acetophenone)and from the naphthols (2-aceto- and 2-benzo-a-naphthol) respectively.The latter substances were prepared by heating 10 grams ofa-naphthol with 15 grams of zinc chloride and 20 grams of aceticor benzoic acid at 150° for half an hour (Friedlander, Ber., 1895, 28,1946).FriedlPnder has characterised 2-aceto-a-naphthol, and showni h t o possess the assigned structure, but the similarly fornied 2-benxo-a--naphthol does not seem t o have been described.I t is obtained in the form of a yellow, amorphous, partly hydrolysedsodium salt on pouring the cold reaction product (see above) intodilute aqueous sodium carbonate ; from this salt the phenol itself canbe isolated as a yellow, crystalline solid, melting, after recrystal-lisation from dilute alcohol, at 77" :C = 66.18 ; H = 9.03.9.38 per cent.C = 53.60 ; H = 7.09.C,,H,,O,S requires C = 53.67 ; €I = 7.32 ; S = 13-01 per cent.melting a t 47O :C=55*25; H z 7 .8 3 .C,,H,,O,S requires C = 55.39 ; H = 7.69 per cent.0,1039 gave 0.3123 CO, and 0.0486 H,O.C17H,,0, requires C = 82.24 ; H = 4.84 per cent.The benxoy1 derivative, prepared by the Schotten-Bizumann method,crystallises from light petroleum i n pale yellow leaflets, melting at154' to a dark red liquid :C = 82.00 ; H = 5.20UNSATURATED GROUPS ON OPTICAL ACTIVITY. PART IV. 2270.1326 gave 0.3969 CO, and 0.0528 H,O.C,,H1,O, requires C = 81.83 ; H = 4.55 per cent.2-Benao-a-naphthol displays a great tendency to form insoluble saltswith bases; the pale yellow, amorphous sodium and ammonium salts,and the yellow, crystalline piperidine salt, melting at 138O, are allpartly hydrolysed by cold water, but the still less soluble, brownish-yellow barium salt is much more stable :C=81*68 ; H = 4'43.0.2571 gave 0.0957 BaSO,.C,,H,,O,Ba requires Ba = 21.71 per cent.The phenolic hydrogen camphorates were obtained according toSchryver's method (Trans., 1899, 75, 661); since, however, i tappeared that his directions for preparing the phenolic sodium saltsmight in some of the present cases give rise to secondary reactions,owing to the presence of metallic sodium, these were prepared byadding the equivalent amount of sodium ethoxide t o the phenol i nalcohol.After evaporating the alcohol and drying the sodium salt ina vacuum on the water-bath, xylene and the requisite amount ofcamphoric anbydride were added. With some of the more complexphenols, too prolonged heating appeared to give rise to by-products,a maximum, although frequently not very satisfactory, yield beingobtained after heating a t 100" for about half-an-hour.Phenyl hydrogen camphorate, C0,H*C8H14-C0,Pb .-Slender needlesfrom methyl alcohol, melting a t 98" (100' : Schryver) :0.1217 gave 0.3096 CO, and 0.0815 H20.0- /3- Beet y lvin y lph en y l hydrogen c a rnphorat e,Ba = 21.91.C = 69.38 ; H = 7-49,Cl6HzOO4 requires C = 69.56 ; H = 7.25 per cent.CO,H-C,H,,~CO,*C,H,.C'H :CHAc.-Soft, yellow plates from alcohol, decomposing at 11 lo :0.1948 gave 0.5006 CO, and 0.1237 H20.o-P-Benxoylvinylphenyl hydrogen camphorate,C = 70.08 ; H = 7.05.C,oH,,O, requires C = 69.76 ; H = 6.98 per cent,CO,H C,H,,*CO,*C,H,*CH: CHBz,was not obtained in very good yield; it forms yellow crystalsfrom benzene by precipitation with light petroleum.The compound,which was rather easily hydrolysed, melted a t 145" :0.1104 gave 0.2961 CO, and 0.0606 H,O.P-NaprlAthyZ hydrogen camphorate, CO2H*C,H,,*CO2*C,,H7.-Purewhite crystals from aqueous alcohol, melting at 125O (121-122O:Schryver) :C = 73.38 ; H = 6-10,C,,H,,O, requires C = 73.89 ; H = 6.40 per cent.0.1128 gave 0.3073 GO, and 0-0740 H,O. C = 74.10 ; H = 7-29.C20H2204 requires C = 73.62 ; H = 6.75 per cent.Q 228 EDMINSON AND HILDITCH : THE EFFECT OF CONTIGUOUSa-Naphthyl hydrogen camphorate, CO,H* C8H14* CO,*C,,H~.-White0.1172 gave 0,3163 CO, and 0.0734 H,O.2-Aceto-a-napl~th$ hydrogen camphorate, CO,H*C,Hl,*CO,*Cl,H,Ac.0.1444 gave 0.3815 CO, and 0.0858 H,O.C,,H,,O, requires C = 71 *74 ; H = 6.52 per cent,2-L'enxo-a-naphthyl Ir ydyogen campho?.ate, CO,H* C, H,,- CO,* Cl,H,FhI-A yellow, crystalline powder from benzene, melting and decomposingat 172O :prisms, which melted somewhat indefinitely at about 170° :C2,H,,04 requires C = 73-62 ; H = 6.75 per cent.U=73.58; H=6*96.-White needles, melting at 102' :Cl=72*05; H=6*60.0,1059 gave 0.2924 CO, and 0.0572 H,O.C27H2605 requires C = 75-34 ; H = 6.05 per cent.The corresponding camphor-/3-sulphonates were all prepared by theSuhotten-Baumann method, using very dilute aqueous sodium hydro-oxide and maintaining the reaction solution at such a temperature thatthe camphor-p-sulphonyl chloride always remained a little above itspoint of fusion.Phenyl car)npr7Lor-P-sulp?~onate, C,oHl,O*SO,Ph, only solidified afterstanding some time in a vacuum, but thereafter crystallised from lightpetroleum in long, radiating, colourless needles, melting at 4s' :C = 75-30 ; H = 6.05.0.1055 gave 0.2414 CO, and 0.0610 H,O.o-P-AcetylvinyZphenyl camphor-/3-suZphonrte,C = 62.38 ; H = 6*42.C16H,c04S requires C = 62.32 ; H = 6.49 per cent.ClOHl5O* SO,* C,H,*CH: CH Ac,was fourid t o be a yellow oil, which would not crystallise, and, asno other means of purification besides crystallisation existed, it couldnot be utilised.o -P-Benoo ylvinylphenyl camphor- /3-s u Zphonate,C1,Hl,O*SO,*C,H;CH:CHf3z,crystallising in yellow needles from benzene, melted a t 102" :0.1000 gave 0.2497 CO, and 0.0548 H,O.~-~..~ap?&yl canziuhoi.-P-sulpronate, C,oH,50*S0,* Cl,H7, crystellised in0.0978 gave 0.2396 CO, and 0,0549 H,O.a - NaphthyZ cantphor - p - sulphorucle, Cl,Hl,0*S0,*Cl,H7,--W hite0.1097 gave 0.2697 UO, and 0.0624 H,O.C20€K2204S requires C = 67-04 ; H = 6.15 per cent.2-Aceto-a-mphth yl cccrr~~f~or-p-suzph~~t~, CloH1,0*80,* CloH6Ac.-C = 68910 ; H = 6.09.C25H2606S requires C = 68.48 ; H = 5-94 per cent.faintly pink prisms from aqueous alcohol, and melted at 100' :C = 66.82 ; H = 6.24.C,,H,,O,S requires C: = 67.04 ; H = 6.15 per cent.needles from dilute alcohol, melting at 109O:C = 67.04 ; H = 6.32UNSATURATED GROUPS ON OPTICAL ACTIVITY. PART IV. 229Small, hard, crenm-coloured needles from nlcohol, which molted fit1 0 2 O :0.1039 gave 0.2510 CO, and 0.0546 H,O.C= 65.90 ; H=5*84.C,2H240,S requires C = 66.00 ; H = 6.00 per cent.2-Benzo-a-napht?hyZ camphor-P-suzphonate \vas not obtained in thesolid stab, and therefore had to be omitted from the series.The polnrimetric observations were carried out exactly RS in previousinvestigations of this series, the temperature being maintained a t 2 3 O .For the alkyl esters, t h e following values were obtained :Chloroform solutions : 5 per cent. - [alw [MID.Methyl hydrogcii caiiiphorate ... + 57'71 -k 123.5Ethyl ,, ... 38.72 88'372-Propyl , , > 9 ... 38.76 93.8'/?-Rlltyl ,, ... 35.60 91.1,,3 , -Ifcan [M]Ei" (ethyl n-hntyl) ............ 91.124 per cent.[.ID.EMID. + 58-50 + 125.239-50 90.738.56 93'333-24 92.892'3--Methyl camphor-8-sn1phonat.e ... + 43.61 + 197.3 + 43-40 + 106.8Ethyl ,, .., 43'91 114-2 43-28 112%In certain instances it was found impossible to obtain an accuratereading with the 5 per cent. solutions of the phenolic esters, andtherefore, especially as in none of the other cases mas there any markedchange of rotatory power on dilution, we give only the valuesmeasured in 2-5 per cent. chloroform solution ; the numbers obtainedby one of us (Zoc. cit.) for the o-tolyl and o-aldehydophenyl estersme incorporated in the table,Hydrogen camphorate.lalo. [MI,. Diff.L r \Phenyl .................. +45*38 +125*2 4-329o-Tolyl .................. 45.0 130'5 38'2o-Alclehydophenyl ......48.1 146.2 53.9o-Acetylvinylplionyl ... 30.04 103.3 12'2o-8-Benxoylvinylphenyl 49.44 200.7 108.4P-Naphthyl ......... 53'25 173'7 81'4a-Naphthyl ............ 34-24 111.6 19.32-Aceto-a-1iaphthyl ... 38.00 139.5 47 52-Benm-a-naphthyl ... 52.82 227'2 134.9'Camphor-B-siilphonate.$40'56 f 1 2 4 - 9 +12-346.0 148.1 35.539-6 133.1 20.527.2 119.1 6.530.16 108'0 - 4 . 638.24 i.37-0 f24'450.02 200.1 87'5i.l,.]L)iff:- - -- - -There are thus included in the above summary four groups of sub-stances, namely, hydrogen camphorates of the phenyl and of the riaphthy 1series, and camphor-P-sulphonates of the same. Of these, the twofirst-mentioned show a steady increase of rotatory power with theincreasing number of conjugated groups, but the camphor-P-sixlphonicseries is, to all appearances, perfectly irregular.These results arefurther confused by the isomeric a- and P-naphthyl compounds, wherethere is a very notable difference of rotation in both the cnmphorioand the camphor-/?-sulphonic series, but in conflicting directions230 EDMINBOM AND HILDITCH : OPTICAT) ACTIVITY. PART IV.Eenzylidenecaniphor * ......... + 1020Cinnamylidenecamphor t ... 788We will refer, in conclusion, to three other series of this tFpe ofcompounds, which would seem to exhaust all the available data ; thefirst comprises the camphorates of certain aromatic arnines, comparedwith di-n-butylamine camphorate ([MI? 38% in 2.5 per cent. chloro-form solution) :Win. Difference.Di-p-toluidine cainphornte ............+ 99 -4 + 60%Di-p-aminoacetophenone camphorate. 91'2 52 '6Di-p-aminobenzophenone camphorate 73.6 35.0Next, there are certain condensation products of camphor witharomatic aldehydes :PJcnsylcamphor * ............ + 348y-Phenylpropylcaniphor I. 178* Haller, Compt. rend., 1899, 128, 1370.I. Rupe and Frisell, Ber., 1905, 38, 104.And, finally, certain esters recently examined by Rupe (Annnlen,1909, 369, 311) :[ Differencc.Mcnthyl diphenylacntate ............ - 233'4 + 75'6 ,, a-phenylcinnnmats ......... 193'5 -t. 35 -7,, fi-pheny!cinnninntc ......... 137'3 -21.5Rupe draws the empirical conclusion that a phenyl group in thenearest possible position to the asymmetric system enhances rotatorypower, but in others, further removed, depresses it ; it appears not alittle remarkable that one and the same group should exert a stronginfluence in two opposing directions, according as it is united with theQ- or y-carbon atoms.We may summarise these data by pointing out that of the elevenseries to which we have referred, four shorn a steady increase, foursbow a decrease, and the remaining three manifest indefinite changesin optical activity on increasing.beyond two the number of contiguousunsaturated systems.Sufficient facts for a profitable discussion as t owhether the indefinite numbers result from conflicting influences otherthan that due to conjugation, or whether the regular series are simplycoincidences, appears still to be lacking.It will be observed that the difference between the esters of evensuch nearly related bodies as phenol and o-cresol are considerable, andone cause of irregularity may lie in the fact that most of the estersstudied above are tbe earlier members of homologous series, and maythus be abnormal, as has so frequently been noticed in the firstmembers of other series. There is, indeed, little doubt that interestingand more comparable results would follow from a study of activeesters of, for example, one of the higher normal aliphatic alcohols,replacing successive methylene groups by a system of multipleTHE CONSTITUENTS OF RED CLOVER FLOWERS. 231identical unsaturated groups, but such a series would be very difficultto prepare.We desire to offer our hearty thanks t o Professor Knorr, in whoselaboratory this work has been carried out.UNIVERSITP OF JENA