696 J. Chem. SOC. (C), 1968 Restricted Rotation about the Aliphatic Carbon-Carbon Bond in 1,2-Disubstituted Tetra-arylethanes By P. J. M. Burchill and N. Thorne," Department of Chemistry, University College, Cathays Park, Cardiff The existence of stable rotational isomers of 1,2-dichlorotetraphenylethane previously reported, i s shown to be incorrect, since dipole moment measurements indicate the presence of the trans-form only. Infrared studies of a number of 1.2-disubstituted tetra-arylethanes fail to account for the existence of possible gauche-forms, except in the case of the ethane-1 ,Z-diols which occur exclusively in this conformation. Chlorine addition reactions with sulphuryl chloride as reagent follow a heterolytic path. RESTRICTED rotation about the aliphatic carbon- carbon bond has been demonstrated by evidence from thermodynamic data,l dipole moments,Z and X-ray diffra~tion,~ electron diffraction: Raman,5 infrared,6 nuclear magnetic resonance,' and microwave spectra.s Theoretically, it should be possible to isolate rotational isomers of highly substituted ethanes the potential energy barriers to internal rotation of which are suffi- ciently large for interconversion of the isomers to be a slow process.This would require a barrier height of 16-20 kcal./mole for a separation at room temperature. A41though a separation has been reported for tetra- bromoethane at low temperature^,^ the only report of an isolation at room temperature has been made by Bassett, Thorne, and Young,lo who claim to have separated trans- and gauche-forms of 1,2-dichlorotetraphenyl- ethane.More recent work by Williams,ll has shown that the high-melting form used in various measurements by these authors, was, owing to the method of preparation, a stable complex of the high-melting dichloride and carbon tetrachloride. However, Williams again con- cludes that the two forms of 1,2-dichlorotetraphenyl- ethane are rotational isomers from evidence such as a positive result from Sidgwick's method,lZ small differ- ences in the refractive indices of equivalent solutions of the two forms, and a mixed melting point depression. In the work reported here we prepared a number of 1,2-disubstituted tetra-arylethanes in high- and low- melting forms, and examined the compounds using modern physical methods. Tetra-$-t olylet hylene,13 and t etra-$-ethylphenyle thyl- ene were prepared by the route involving the pinacol- pinacolone and the retropinacol rearrangements from the respective ketones.The former ethylene was also Mg-Mgl I* EtMgBr RCOR ___t R,C(OH).C(OH)Rz _+ RaCCOR -- I* R,C.C(OH)HR __t R,C:CR, prepared by the dehydration of 1,1,2,2-tetra-$-tolyl- ethanol, formed by the action of lithium di-$-tolylketyl 1 E. N. Lassettre and L. B. Dean, J . Chem. Phys., 1949, 17, 317. 2 S. Winstein and R. E. Wood, J . Amer. Chem. SOC., 1940, 62, 548. J. D. McCullough, J . Amer. Chem. SOC., 1940, 62, 480. 4 I. Morino and M. Iwasaki, J . Chem. Phys., 1949, 17, 217. W. F. Edge11 and G. Glocker, J . Chem. Phys., 1941, 9, 375. ti J. K. Brown and N. Sheppard, Trans. Faraduy SOC., 1952, N. Sheppard and J.J. Turner, Proc. Roy. Soc., 1959, A252, 48, 128. 506. * D. R. Herschbach, J . Chem. Phys., 1956, 24, 358. on chloro-di-$-t ol yme t hane . Te traphen yle t h ylene ,14 and t etra-$-fluorophenylet hylene were prepared by the action of copper bronze on the corresponding dichloro- methane. According to Johnson et aZ.,15 tetra-p-fl ioro- phenylethylene melts at 189", but by careful purific ition of the starting materials we obtained the ethylene melting at 203". Its identity was confirmed by elerr ental analysis, oxidation with chromium trioxide to 4,4'-di- fluorobenzophenone in 78% yield, and by reduction to 1 , 1 ,2,2-t etra-$-fluorophen yle t hane. High- and low-melting forms of the 1,2-dichlorotetra- arylethanes were prepared by the action of either chlorine or sulphuryl chloride on solutions of the et hylenes.With tetra-$- tolylet hylene and t e tra-$-et hylphenyl- ethylene, chlorine gave the low-melting form of the dichloride, while sulphuryl chloride gave the high- melting form. The reverse was found for tetraphenyl- ethylene, while tetra-$-fluorophenylethylene yielded one form of the dichloride only. The high-melting form of 1,2-dichlorotetraphenylethane was also prepared by the action of sodium iodide on benzophenone dichloride. l6 The identity of the dichlorides was confirmed by elemental analysis, 1H n.m.r. and i.r. spectroscopy, and oxidation by chromium trioxide to give the related ketones in good yield. Mild hydrolysis of the dichlorides gave the corre- sponding ethylene oxide. I t has been suggested that addition reactions involving sulphuryl chloride proceed by a homolytic path, and are catalysed by the presence of per0xides.l' We have investigated the reaction between sulphuryl chloride and tetraphenylethylene at 20°, and find that the rate is affected by the polarity of the solvent, but not by the presence of peroxides (Table 1).Electron spin resonance investigations also fail to indicate the presence of free radicals. Since it has been shown that certain sub- stitution reactions with sulphuryl chloride are due to electrophilic attack by the reagent,ls we consider that the reaction proceeds through the intermediates (I) 9 R. E. Kagarise, J . Chem. Phys., 1956, 24, 300. 10 H. L1. Bassett, N. Thorne, and C . L. Young, J . Chem. SOC., 11 G. T. Williams, Ph.D.Thesis, University of Wales, 1962. 12 N. V. Sidgwick, J . Chem. SOC., 1915, 672. la W. E. Bachmann, J . Amer. Chem. SOC., 1933, 55, 3857. l4 Org. Synth., 1951, 31, 104. 15 L. V. Johnson, F. Smith, M. Stacey, and J. C . Tatlow, J . l6 H. Finkelstein, Ber., 1910, 43, 1533. 17 M. S. Karasch and H. C. Brown, J . Amev. Chem. SOC., 1939, 18 R. Bolton, P. B. D. de La Mare, and H. Suzuki, Rec. Trav. 1949, 85. Chem. SOC., 1952, 4710. 61, 3432. chim., 1966, 85, 1206.Org. 697 and (11) involving the formation of a donor-acceptor charge-transfer complex with the ethylenic double bond. In such a scheme an increase in the polarity of TABLE 1 Effect of solvent on the reaction between sulphuryl chloride and tetraphenylethylene Dichloride yield (%) 98 67 60 Nil Time ..................1 hr. 24 hr. 7 days 7 days Solvent CHCl, C,H5CI Cc1, C6H6 the solvent will stabilise any ion-forming reaction, and push the reaction to completion, while such a reaction will be unaffected by peroxides. A dipole-moment determination on the two forms of 1,2-dichlorotetraphenylethane has been made using the method suggested by Guggenheim.lg The dielectric constants of the solutions were measured with apparatus R R \ / R R \ / small dipole moment, 0-77 D units. This dichloride must therefore exist in the trans-form, since calculation re- quires a dipole of around 3 D units for the gauche- conformation. Proton magnetic resonance spectroscopy is of little help in studying rotational isomerism in compounds of this type, since only long-range effects could be expected, and in fact it is found that the high- and low-melting forms of each dichloride give identical spectra.It is also seen that the high- and low-melting forms of each dichloride have identical i.r. spectra, and only one reasonably strong absorption occurring at 633 cm.-l 2 cm.-l is observed which is not also present in the spectra of the corresponding ethanes. From a study of the model compound 2,3-dichloro-2,3-dimethylbutane, the carbon-chlorine stretching vibrations of the trans- form is seen as a peak at 618 cm.-l, while peaks at 650 R R R \ / /--\ 0 0 described by Davidson,20 and the refractive indices with an Abb6 refractometer (Table 2). TABLE 2 Dielectric constants and refractive indices of solutions of 1,2-dkhlorotetraphenylethane in benzene W EO2O E1200 (n12 - ?Z02) (El - Eo)/W (n12 - no"/w 0.00638 t 2.28440 2.25819 0.00240 0.5943 0.3764 0.02562 * 2.28482 2.29621 0.01021 0.4445 0.3985 0.02366 t 2.28345 2.29381 0.00870 0.4379 0.3678 0.00524 * 2.28419 2-28676 0.00180 0.4909 0.3438 0.03717 * 2.28398 2.29932 0.01382 0.4128 0-3719 * Measurements using dichloride, m.p. 186". t Measure- ments using dichloride, m. p. 172". The symbols used denote the following quantities: w weight fraction, E dielectric constant, n refractive index. The subscripts 0 and 1 refer to the solvent and solution respectively. Plotting the functions ( E ~ - E ~ ) / W , and (n12 - no2)/w, against weight fraction, and extrapolating to infinite dilution, gives the value for ( A / W ) ~ + ~ = [(cl - E ~ ) - (n12 - fiO2)]/w as 0.165.The di- pole moment is then calculated from the expression : 1036 W T p2 = -.-. ~ ._. N 4x ( E ~ + 2)2 do (:Lo where M is the molecular weight of the solute, and do is the density of the solvent. The results show that the two forms of 1,2-dichloro- tetraphenylethane are indistinguishable and have only a l9 E. A. Guggenheim, Trans. Faraduy Soc., 1951, 47, 573. 2o D. W. Davidson, Canud. J . Chenz., 1967, 35, 455. z z Cl CI - S' 0 CI CI and 568 cm.-l denote the carbon-chlorine stretching vibrations of the gauche-forms. Since these latter peaks are not present in the spectra of the dichlorides, it must be concluded that the molecules exist only in the symmetrical form, and the absorption occurring at 633 cm.-l must be assigned to the carbon-chlorine stretching mode of the trans-conformation.In addition, the complete identity of solution- and solid-phase spectra of these compounds indicates that the trans-form must be appreciably more stable than the possible gauche- forms . 21s 22 The application of Sidgwiclts method for distinguishing between dimorphs and isomers to the high- and low- melting forms of each dichloride shows that the least soluble form of each pair is slightly soluble in a saturated solution of the more soluble form. However this solu- bility is found to be within the range of experimental error so that the results become inconclusive. It can also be shown that the high- and low-melting forms of the dichlorides are not dimorphs, since in the case of 1,2-dichlorotetraphenylethane, and 1,Z-dichloro- tetra-$-tolylethane, the X-ray powder patterns of each pair are identical.The absence of additional lines in the powder patterns of the low-melting forms suggests that impurities are not present. Analysis by t.1.c. also fails to show the presence of impurities, but repeated recrystall- isation of the low-melting forms eventually raises their melting points. At first, it was considered that this change was due to isomerisation. However, in order to 21 San-Ichiro Mizushima, ' Structure of Molecules and Internal 22 N. Sheppard, Adv. S$edrosco$y, 1959, 1, 288. Rotation,' Academic Press, New York, 1954.698 J. Chem. SOC. (C), 1968 account for the existence of two forms of the dichlorides, it must be concluded that the low-melting forms contain minute traces of impurity, which catalyses their thermal decomposition, causing them to melt with decomposition at lower temperatures.The action of peracetic acid, perbenzoic acid, and a mixture of formic acid and hydrogen peroxide, on a number of tetra-arylethylenes has been investigated, since it is well known that hydroxylation of olefins by peracids is by addition in the trans sense. However, it was found that all these reagents give the corresponding ethylene oxide, which tends to be very unreactive, and resists the action of reagents (water under high temper- ature and pressure, methyl magnesium iodide, and alcoholic potassium hydroxide) employed in attempts to open the ring to give the desired diol. Eliel and Rerick,% record that tetraphenylethylene oxide does not react with lithium aluminium hydride. The formation of 4,4',4",4"'-tetra(dimet hy1amino)- benzopinacol from 4,4'-dimethylaminobenzophenone has been investigated, since it has been shown that cis- and trans-forms of diols can be produced by methods em- ploying different reducing agentsJ2* and this diol melting at 210" has been prepared by C ~ h e n , ~ ~ using aluminium amalgam as reducing agent, while Gomberg and Bach- mann,26 using magnesium-magnesium iodide, have isolated the same diol melting at 196".We have found that reduction with aluminium amalgam gives a white crystalline compound melting at 205", while reduction with magnesium-magnesium iodide gives a pale green product melting a t 196", which after careful purification becomes colourless and melts at 205". Further proof of the identity of the two products is given by the i.r.spectra, both of which have absorption peaks at 3564 (strong), and 3610 cm.-l (weak), corresponding to the intramolecular hydrogen bonded hydroxy, and the free hydroxy respectively. The i.r. spectra of 4,4"4'"4'''- tetramethylbenzopinacol, and 4,4',4",4"'-tetraethyl- benzopinacol have also been examined, and the presence of free, and intramolecular hydrogen-bonded hydroxy- groups is again seen, with absorption peaks similar to the above values. For benzopinacol, Kuhn 27 found values of 3608 and 3567 cm.-l, for the free and bonded hydroxyl respectively. The presence of intramolecular hydrogen-bonding in these diols shows that they must exist in the gauche conformation since, in such com- pounds, hydrogen bonding can occur only in this form. The gauche-form is thus stabilised so that it is of lower energy than the trans-form.EXPERIMENTAL The lH n.m.r. spectra were recorded on a Perkin-Elmer R10, 60 Mc./sec. spectrometer in deuteriochloroform, with tetramethylsilane as internal reference. The i.r. spectra were recorded on a Perkin-Elmer 337 spectrometer, the dichloride spectra as Nujol mulls and solutions in benzene 23 E. L. Eliel and M. N. Rerick, J. Amer. Chem. SOC., 1960, 82, 1362. z4 G. Wittig and W. Weimer, Bey., 1931, 64, 2405; P. D. Rartlett and R. F. Brown, J. Amer. Chem. SOC., 1940, 62, 2927. and chloroform. Light petroleum refers to the fraction of 1,2-DichZorotetraphenyZetha1ze.-(a) The ethylene (10 g.), in chloroform (100 ml.), was treated with chlorine for 1 hr.Crystallisation of the product twice from light petroleum- dichloromethane (1 : 1) gave the dichloride (12 g.), m. p. 172" (decomp.) [Found: C, 77.4; H, 4.85; C1, 17.6%; M (cryoscopic in benzene), 395. Calc. for C,,H,,Cl,: C, 77-4; H, 4.95; C1, 17.6%; M , 4031, vmx. 632 cm.-l (b) Dichlorodiphenylmethane (20 g.) in acetone (50 ml.) was added to a solution of sodium iodide (14 g.) in acetone (250 ml.) a t room temperature. After 48 hr. the precipitate was collected, washed with aqueous sodium thiosulphate and then dissolved in chloroform; the solution was dried (CaC1,) and evaporated. The product was crystallised twice from light petroleum-dichloromethane (1 : 1) to give the dichloride (9.6 g.), m. p. 186" (decomp.) (Found: C, 77.6; H, 4.9; C1, 17.65%; M , 397); i.r.and 1H n.m.r. spectra identical with previous dichloride. Tetra-p-fluorophenyZetJzyZene.-Dichlorodi-p-fluorophenyl- methane from 4,4'-difluorobenzophenone (10 g.) and phos- phorus pentachloride (20 g.) was dissolved in dry benzene (100 ml.) and copper bronze (20 g.) was added. After being heated under reflux for 2 hr, the solution was filtered whilst hot, and then evaporated to give the ethylene (10 g.), m. p. 203" (from ethanol) (Found: C, 77.0; H, 4-05; F, 19.2. C,,Hl,F4 requires C, 77.2; H, 3.95; F, 18.8y0). 1,2-DichZorotet~a-p-fluoro~JienyZethane.- Tetra-p-fluoro- phenylethyiene (1 g.) in chloroform (50 ml.) was set aside a t room temperature for 72 hr. after being treated either with a slow stream of chlorine for 2 hr. or with sulphuryl chloride (0-4 ml.).The solvent was removed and the residue was crystallised from light petroleum-dichloro- methane (1 : 1) to give the dichloyide (0.9 g.) as prisms, m. p. 168" (Found: C, 65.75; H, 3.8; C1, 15.3; F, 15.8. C26Hl,C12F4 requires C, 65.7; H, 3-4; C1, 14-95; F, 16-0y0). vmx. 630 cm.-l (C-Cl). Tetra-p-fluoro- phenylethylene (1 g.) in ether (50 ml.) and ethanol (50 ml.) was treated with sodium (1 g.) during 2 hr. The solution was washed with water, dried (K,CO,), and evaporated. Crystallisation of the residue from benzene-ethanol (1 : 1) gave the ethane (1 g.), m. p. 281" (Found: C, 76.75; H, 4.4; F, 18.55. C,,Hl,F4 requires C, 76-85; H, 4-4; F, 18.7y0). Tetra-p-fluorophenyletlzylene Oxide.-(a) Tetra-p-fluoro- phenylethylene (1 g.) in chloroform (50 ml.) and 40% per- acetic acid (5 ml.) was heated to 60" for 48 hr.The solution was washed with dilute alkali and water, and was then dried (CaCl,) and evaporated. Crystallisation of the residue from ethanol gave the ethylene oxide (0.8 g.) as needles, m. p. 208" (Found: c, 74-35; H, 3.9; F, 18.0. C,,HI6F4O requires C, 74.3; H, 3.8; F, 18.1%). (b) A solution of 1,2-dichlorotetra-P-fluorophenylethane (0.5 g.) in dioxan (10 ml.) and water (40 ml.) was heated to 60" for 24 hr. and then poured into water, and the product was extracted with ether. The ether was removed to give the ethylene oxide (0.4 g . ) , m. p. 208" (from ethanol); identical (mixed m. p. and i.r. spectra) with the previous compound. b. p. 40-60". (C-cl) ; T 3.05-2.50 (CeH5). 1 , 1 ,2,2- Tetm-p-fluorophenylethane .- 25 N.D. Cohen, Rec. Trav. chim., 1919, 38, 121. 26 M. Gomberg and W. E. Bachmann, J. Amer. Chem. SOC., 27 L. P. Kuhn, J. Amev. Chenz. SOC., 1952, 74, 2492. 1927, 49, 236.Org. 1, 1,2,2-Tetra-p-toZyZethanoZ.-To a cooled solution of lithium di-P-tolylketyl, from di-p-tolyl ketone (6 g.), lithium (0.4 g.), and dry ether (100 ml.), chlorodi-p-tolyl- methane (5 g.) in ether (50 ml.) was added during 1 hr. The mixture was heated under reflux for 2 hr. and then decomposed with ethanol and poured into water (1 1.). The ethereal layer was washed with water, dried (Na,SO,), and evaporated, and the residue was fractionally crystallised from benzene-ethanol (1 : 1). The first fraction was recrystallised from chloroform-ethanol (1 : 1) to give 1,1,2,2-tetra-P-tolylethane (2 g.), m.p. 282", identical (mixed m. p. and i.r. spectra) with an authentic sample. The second fraction on crystallisation from chloroform- ethanol (1 : 1) gave prisms of 1,1,2,2-tetru-p-toZyZethunoZ (4-5 g.), m. p. 222" (Found: C, 88.9; H, 7.7. C30H300 requires C, 88.7; H, 7.4%), T 7.68 (CH,), 7.25 (OH), 4.80 (CH), and 3.14-2.60 (complex tolyl resonances). Tetra-p-toZylethy1ene.-1, 1,2,2-Tetra-~-tolylethanol (4.5 g.) was heated under reflux with acetyl chloride (20 ml.) for 30 min., and the solution was then evaporated to dryness to give the ethylene (4-2 g.), m. p. 150" (from ethanol) (Found : C, 92.5; H, 7.55%. Calc. for C,,H,,: C, 92.8; H, 7.2%). 1,2-Dichlorotetra-p-tolylethane.-(a) Chlorine was passed into a solution of tetra-p-tolylethylene (1 g.) in chloroform or carbon tetrachloride (50 ml.) for 15 min.The solvent was removed to leave the dichloride (0.9 g.) [from benzene- acetone (1 : l)], m. p. 183" (decomp.) [Found: C, 78.1; H, 6.1; C1, 15.7%; M (cryoscopic in benzene), 456. C3,H,,C12 requires C, 78.4; H, 6.1; C1, 15.5%; M , 4591. v,,,, 634 cm. (C-Cl) ; T 7.67 (CH,), and 3.17-2.70 (complex tolyl resonances). (b) Tetra-P-tolylethylene (1 8.) in 1,1,2,2-tetrachloro- ethane (20 nil.) was treated with sulphuryl chloride (0.35 ml.) a t 0", and was then set aside, with occasional shaking, for 3 hr. The precipitate was washed with light petroleum to give the dichloride (0.7 g.), m. p. 146" (decomp.) [Found: C, 78.7; H, 5.95; C1, 15.3%; M (cryoscopic in benzene), 4691; i.r. and IH n.m.r. spectra were identical with the previous compound.Tetra-p-tolylethylene Oxide.-This was prepared from the corresponding ethylene or dichloroethane as previously described. The product was crystallised from benzene- ethanol (1 : 1) to give the ethylene oxide as needles, m. p. 210" (Found: C, 89.1; H, 6.95. C,,H,,O requires C, 89.1; H, 7.15%). 4,4', 4",4"'-TetraethyZbenzopinacoZ.- 4,4'-Diethylbenzo- phenone (20 g.) in ether (50 ml.) and benzene (50 ml.) was added to a magnesium-magnesium iodide reducing agent prepared by Gomberg and Bachmann's method 26 from magnesium (8 g.) and iodine (21 g . ) in ether (50 ml.) and benzene (50 ml.), The mixture was shaken for 20 min. a t room temperature, and was then poured into aqueous ammonium chloride at 0". The organic layer was dried (Na,SO,) and evaporated to give an oil which solidified on cooling.Crystallisation from chloroform-methanol (1 : 1) gave the dioZ (16 g.), m. p. 143" (Found: C, 84.85; H, 7.95%. C,,H,,O, requires C, 85.35; H, 7-65%), vmx. (CCl,) 3620 (free OH) and 3578 cm.-l (intramolecular bonded O-H). 4,4', 4", 4"', Tetramethy1benzopinacoZ.-This was prepared from 4,4'-dimethylbenzophenone as above. Crystals from chloroform-methanol (1 : l), m. p. 175", v,, (CC1,) 3615 (free OH) and 3572 cm.-1 (intramolecular bonded O-H). 1, 1, 1,2-Tetra-p-ethyZphenyZethan-2-one.- 4,4',4",4"'- Tetraethylbenzopinacol (20 g.) in acetic acid (100 ml.) was heated under reflux for 1 hr. with a crystal of iodine. The precipitate which separated on cooling was recrystallised from ethanol to give the ketone (18 g.), m.p. 83" (Found: C, 87.95; H, 7-8. C3&@ requires C, 88.7; H, 7 ~ 8 % ) ~ vmxa 1667 cm.-l (GO). 1, 1 , 1 ,2- Tetra-p-ethyZ~henylethunol.-The above ketone (2 g.) was reduced with ethyl magnesium bromide from ethyl bromide (10 ml.), magnesium (2.5 g.), and ether (50 ml.) . The solution was set aside a t room temperature for 30 min. and then heated under reflux for 1 min. ; it was then cooled and decomposed with ice-hydrochloric acid. The ethereal layer was separated, dried (Na,SO,), and evaporated to give the alcohol (1.8 g.) as an oil which could not be purified further, but was identified by its i.r. spectrum. vmX 3630 cm.-I (OH). Tetra-p-ethyZphenyZethyZew .-The above alcohol (2 g.) , in acetic acid (20 ml.), was heated under reflux with a small crystal of iodine for 1 hr.The hot solution was decolourised with sulphur dioxide and cooled to yield a precipitate, which was washed with methanol. Crystallisation from ethanol gave the ethylene (1.4 g.) as needles, m. p. 137" (Found: C, 92.1; H, 8-2. C,,H,, requires C, 91.9; H, 8.1 yo). 1,2-0iclzlorotetra-p-ethyl~henyZethane .-(a) Chlorine was passed into a solution of tetra-p-ethylphenylethylene (1 g.) in chloroform or carbon tetrachloride (50 ml.) for 15 min. Removal of the solvent and crystallisation of the residue from light petroleum-dichloromethane (1 : 1) gave the di- chloride (0-8 g,), m. p. 159" (decomp.) [Found: C , 79-4; H, 7.2; C1, 14.2%; M (cryoscopic in benzene), 508. C,4H,,C12 requires C, 79.2; H, 7.0; C1, 13.8%; M , 5151, v , , ~ . 635 cm:l (C-Cl), 'c 8-75 (CH, triplet J = 7.5 c./sec.), 7.36 (CH, quartet J = 7.5 c./sec.) and 3.1&2.60 (C,H,).(b) The ethylene (1 g.) in 1,2-dichloroethane (20 ml.) was treated with sulphuryl chloride (0.35 ml.) at 0", and was then set aside for 3 hr. The precipitate which formed was recrystallised quickly from light petroleum-dichlorometh- ane (1 : 1) to give the dichloride (0-7 g.), m. p. 122" (decomp.) [Found: C, 78-8; H, 7-2; C1, 14.2%; M (cryoscopic in benzene), 4991; i.r. and IH n.m.r. spectra were identical with preceding dichloride. Tetra-p-ethyZphenylethyZene Oxide.-This was prepared from the corresponding ethylene or dichloroethane as previously described. The product was crystallised from benzene-ethanol (1 : 1) to give the ethylene oxide as needles, m. p. 152" (Found: C, 89.1; H, 8.0.C,,H3@ requires C, 88.7; H, 7.85%). Di-p-ethyZ9henyZmethyZ Chloride.-Di-p-ethylphenylmeth- anol (6 g.) in benzene (20 nil.) was heated under reflux with thionyl chloride (10 ml.), for 30 min. Removal of the sol- vent left an oil which was distilled under reduced pressure to give the methyl chloride (5 g.), b. p. 143"/0-1 mm. (Found: C, 78.85; H, 7-5; C1, 13.7. C1,Hl,Cl requires C, 78.9; H, 7.35; c1, 13.75%). 1,1,2,2-Tetra-p-ethyZphenyZethane.- Di-p-e thylphenyl- methyl chloride (5 g.) in ether (50 ml.) was treated with magnesium according to the method described by Gilman and Kirby.28 The product was crystallised from ethanol to give the ethane (3 g.), m. p. 156" (Found: C, 91.2; H, 8.45. C34H3, requires C, 91.4; H, 8.6%). 4,4',4~',4"'-Tetra(dimethylum~no)benzo~~nucoZ.-(u) 4,4'- Dimethylaminobenzophenone (5 g.) in ethanol (1 00 ml.) was treated with aluminium amalgam (10 g.) .25 The product 28 H. Gilman and J. E. Kirby, J . Amer. Chem. SOC., 1926, 48, 1733.700 (2.5 g.) was crystallised from acetone to give the diol, m. p. 205" (Found: C, 75.95; H, 7.5; N, 10.45. Calc. for C,,H,,N,O,: C, 75.85; H, 7.8; N, 10*4%), vmX (CCl,) 3610 (free OH), 3564 cm:l (intramolecular bonded O-H). (b) 4,4'-Dirnethylaminobenzophenone (45 g.) in ether (50 ml.), and benzene (50 ml.) was treated with a mag- nesium-magnesium iodide reducing agent prepared from magnesium (15 g.) and iodine (39 g.) in benzene (100 m1.).2s The product from ethanol gave pale green crystals of the diol (11 g.), m. p. 195-197". Further recrystallisation J. Chem. SOC. (C), 1968 from benzene-ligroin (1 : I), dichloromethane-ethanol (1 : 1) and finally acetone gave the diol as white crystals, m. p. 205" (Found: C, 75.6; H, 7.7; N, 10.5%); the i.r. spec- trum was identical with that for the preceding compound. One of us (P. M. J. B.) wishes to thank the D.S.I.R. for a maintenance grant, and also Dr. Davidson, N.R.C. Ottawa, for his advice on the dipole moment measurements. [7/956 Received, July 31st, 19671