362 TRANSACTIONS OP SECTION B. 



a considerable amount of preliminary experimental work we decided that the 

 most suitable compound belonging to this particular class is the 1 -methyl ryrjo- 

 hexylidene-4-acetic acid : — 



CHjv ,CH, . CH.A /H 



w x ch,.ch/ n co.,h. 



The reason why this decision was arrived at is that, whilst l-methylcycfo- 

 hexylidene-4-acetic acid contains no asymmetric atom in the molecule, but never- 

 theless possesses an enantiomorphous molecular configuration, it appeared possible 

 to devise a method for its synthesis : and since it should be distinctly acidic in 

 character it would be expected that its resolution could be effected by crystal- 

 lisation with an optically active alkaloid. 



We therefore devised a process for the synthesis of this acid. 1 Curiously 

 enough, however, whilst we were occupied with this work, Marckwald and Meth - 

 indicated that they had also decided to prepare l-methylcyefohexylidene-4-acetic 

 acid and to resolve it into optically active components in order to realise the 

 most general case of optical activity, and described the method by means of 

 which they had synthesised and resolved the substance. The methods of syn- 

 thesis adopted by Marckwald and Meth, on the one hand, and by ourselves on 

 the other, were quite different and yielded quite different products; our acid 

 melted at 66°, whilst that of Marckwald and Meth melted at 40-41°. We were, 

 however, convinced that our method of synthesis yielded the compound of the 

 constitution stated above and that Marckwald and Meth's acid was the isomeric 

 1-metliyl- A s -fi/<7«hexene-4-acetic acid of the constitution : — 



CH 3V /CHj . CH ,>. 



)C< }C.CH,.CO,H. 



TL' M3H..CH/ 



An acid of the above constitution obviously contains an asymmetric carbon 

 atom and hence should be resolvable, as Marckwald and Meth found, into opti- 

 cally active components in the same way as large numbers of similarly consti- 

 tuted substances. We therefore disputed Marckwald and Meth's contention that 

 their acid was l-mcthylcyc/ohexylidene-4-acetic acid, 3 and in reply these 

 authors* produced further evidence in support of their view; they had in this 

 the support of Wallach, who was then of opinion that their acid had the con- 

 stitution which they had assigned to it. 



The difference of opinion briefly referred to above gave rise to a long con- 

 troversy and led to an extended series of experimental investigations. 5 The 

 final result of this work was to prove conclusively that the original view taken 

 by us was correct; the acid melting at 66° is the true l-methylcyc/ohexylidene-4- 

 acetic acid, whilst the acid melting at 40-41°, which Marckwald and Meth sup- 

 posed to be the latter acid, is the 1-methyl- A 3 -^2/c?ohexene-4-acetic acid, the 

 graphic formula of which contains an asymmetric carbon atom. 



After our original view had been shown to be correct an improved method 

 of preparing our acid was devised and its resolution effected by crystallisation 

 with brucine. The d- and 1-isomerides of l-methyl-rycfohexylidene-4-acetic acid 

 were ultimately obtained of the specific rotatory power [n n , D + or —81*1°; each 

 optically component melted at 52°'5 — 53° and the externally compensated mix 

 ture of the two at 66°. 



1 Perkiu and Pope, Trans. Chem. Soc, 1908, 93, 1075. 



2 Ber., 1906, 39, 1171. 



3 Proc, Chem. Soc, 1908, 22, 107. 



4 Ber., 1906, 39, 2404. 



5 Marckwald and Meth, Ber., 1906, 39, 1171, 2035, 2404; Wallach, Annalen, 

 1907, 313, 311 ; 1909, 365, 255; Perkin and Pope, Trans., 1908,93, 1075; Harding, 

 Perkin and Haworth, Trans., 1908, 93, 1943; Hope and Perkin, Trans., 1909, 95, 

 1360. 



6 Perkin, Pope, and Wallach, Trans., 1909, 95, 1789. 



