ON THE STUDY OF HYDRO-AROMATIC SUBSTANCES. 265 



resolved into active modifications by fractional crystallisation of the 

 cinchonine salts. It was obtained by the removal of the elements of 

 water from methy ley clohexanol acetic acid, which, as pointed out by 

 Perk in and Pope,' may take place in one of two ways : — 



CH . CH, CH . CH3 CH . CH3 



, /\ y\ y\ 



II II II 



CH2 CH., ^ CH2 CH2 CH, CH 



\/ ^ \/ "* \^ 



C C . OH C 



II I I 



CH . COOH CH., . COOH CH„ . COOH 



These latter authors have been engaged in an attempt to prepare a 

 sub.stance which, while not containing an asymmetric carbon atom, is yet 

 capable of existing in optically active modifications, and one of the 

 substances selected for examination was methylcyj/ohexylideneacetic acid. 

 This was prepared from ethyl hexahydro-;o-toluate as starting point, and 

 which on reduction with sodium and alcohol gives hexahydro-^-tolylcar- 

 binol 



vCHg — CHo\ 

 CH, . CH< >CH . CHjOH 



\CHj-CH./ 



This carbinol is readily converted into hexahydro-jo-tolyl bromide, 

 which, when heated with potassium cyanide and the product hydrolysed, 

 yields hexahydro-^-tolylacetic acid 



•CHg CHnV 



CH3 . CH< >CH . CH., . COOH 



^CHj-CH/ 



Bromine acts on the corresponding acid chloride with formation of 

 o-bromohexahydrop-tolylacetic acid, and the ester of this bromo-acid is 

 decomposed by boiling with diethylaniline into hydrogen bromide and 

 ethyl methylc3/c?ohexylideneacetate. On hydrolysis the free acid is 

 obtained melting at 70°-71°, and the method of preparation leaves no 

 doubt that its constitution is represented by the formula 



yCHg — CHoy 



CH3 . CH< " >C = CH . COOH 



\CH,-CH/ 



The acid described by Marckwald and Meth is possibly the isomeric 

 acid 



/CHo-CHv 

 CH3 . CH<; " '^C-CH^ . COOH 



^CH,-CH/ 



Chloro- or iodohexahydrobenzene reacts with ethyl sodiocyanacetate 

 or ethyl sodiomalonate in xylene solution, and from either of the resulting 

 condensation products cyclohexylacetic acid maybe obtained on hydrolysis.^ 



Ethyl isophoroncarboxylate '' obtained by the condensation of ethyl 



' Pruc. as., 1900, 22, 107. 



^ Freundler and Damond, Comjd. Rend., 1905, 141, 593. 



' D. R. P., 148080. 



