122 Messrs Jones and Kewley, Stereochemistry of Benzene. 



Note on the Stereochemistry of Benzene. By H. 0. Jones, M.A., 

 Clare College, and J. Kewley, B.A., King's College. 



[Read 2 March 1903.] 



The question whether derivatives of benzene can shew optical 

 activity, due to the asymmetry of the carbon atoms in the ring, 

 or not, is one of great importance in deciding the constitution 

 of benzene and its derivatives. According to the constitutional 

 formulae proposed by Ladenburg, Claus and Vaubel, in all of 

 which the six carbon atoms are not in a plane and each is singly 

 linked to three other carbon atoms, all meta (1.3) disubstituted 

 derivatives, and all trisubstituted derivatives have no plane of sym- 

 metry : such compounds should therefore be capable of existing 

 in two enantiomorphously related, optically active forms, and, if 

 they do not, these formulae are excluded. According to the 

 other formulae proposed by Kekule, Collie and others, in which 

 all the carbon atoms are supposed to lie in the same plane or 

 the molecule is assumed to be in a continual state of transition, 

 such optical activity would not be expected. 



The fact that naturally occurring derivatives which have the 

 necessary structure, such for instance as vanillin 



C 6 H 3 (CHO) (OCH 3 ) (OH) (1.3.4), 



have never been found shewing optical rotatory power, even when 

 prepared from compounds that are themselves optically active, is 

 fairly strong evidence against the possibility of its occurrence. 



The subject has also been attacked experimentally by several 

 observers. 



Le Bel {Bull. Soc. Ghem. 1882, xxxviii. 98) tried to resolve 

 orthotoluidine by means of living organisms ; Lewkowitsch (Jour. 

 Chem. Soc. 1888, liii. 781) attempted to resolve various substituted 

 benzoic acids by the fractional crystallization of their salts with 

 certain alkaloids ; V. Meyer with Liihn and Sudborough (see 

 Meyer and Jacobsen, Lehrbuch, II. 64) also tried some penta sub- 

 stituted benzene acids ; but in all these cases no activity could 

 be observed. 



It has, of late, been shewn repeatedly that the methods 

 introduced by Pope and his colleagues, which depend on the 

 use of a strong acid and non-hydroxylic solvents, thus elimi- 

 nating the effects of hydrolytic dissociation, have been successful 

 in resolving compounds into their active components when the 

 older methods had entirely failed to do so. Therefore it was 



