ON THE STUDY OF HYDRO-AROMATIC SUBSTANCES. 



259 



(5), previously obtained by him from the oxidation of isolauronolic acid/ 

 CHa-C(CH,)j CHj-C(CH3)j CHj-C(CH,)„ 



C. CH, 



CO . CH, (5) 



CH,-CH 



CH3-COOH 



COOH (6) 



CH2-COOH 



and this ketonic acid, on further oxidation, gave aa-dimethylglutaric 

 acid (6). As Blanc says, the formation of y-acetyldimethylbutyric acid 

 by the oxidisation of isolaurolene shows that it can only have the con- 

 stitution represented by formula 2 and no other. Yet Zelinsky and 

 Lepeschkin, in 1901, did not accept this conclusion, but regarded iso- 

 laurolene as a six-ring compound. 



Accepting then formula 2 for isolaurolene, the next step was to prove 

 that when isolaurolene was treated with fuming hydriodic acid at a 

 temperature of 120° to 125° no change in the nature of the ring was 

 produced. For this purpose the hydriodide was treated with diethyl- 

 aniline, when it readily lost the elements of hydrogen iodide, giving an 

 unsaturated hydrocarbon CgH,.,, boiling at 108°-108'5°, and possessing 

 properties identical with those of isolaurolene. In order that there should 

 be no doubt on this point, the hydrocarbon was oxidised with potassium 

 permanganate, when it yielded y-acetyldimethylbutyric acid, and this, 

 on further oxidation with sodium hypobromite, gave aa-dimethylglutaric 

 acid. These are the same products as Blanc obtained by the oxidation of 

 isolaurolene {see above), and conclusively prove that no isomeric change 

 takes place during the production of the hydriodide, which must therefore 

 have one of the following formulae : — 



CH, - C(CH,)2 CH, - C(CH,), 



I I 



CH . CH, or CI . CH, 



I I 



CHj-CHI CHj-CHj 



There is, moreover, no reason to suppose that heating this hydriodide 

 «vith zinc dust in aqueous alcoholic solution would produce a change in 

 the construction of the ring, and this is proved by the fact that when the 

 resulting hydrocarbon (dihydroisolaurolene) is oxidised with diluted nitric 

 acid it gives rise to aa-dimethylglutaric acid : — 



(7) 



CHj- C(CH,), 



I 

 CH . CH, 



CH,-CH, 



CH^-CCCH,), 



I 

 COOH 



CH2-COOH 



CH.-CCCH,), 



I 



C .CH, 



II 

 CHj-C . COOH 



that is, to the same oxidation product as isolauronolic acid yields when 

 treated with diluted nitric acid.^ 



These experiments prove conclusively that dihydroisolaurolene is a 

 pentamethylene derivative, and is 1:1: 2-trimethylcyclopentane (7), a 

 deduction which receives striking confirmation from the magnetic rotation 

 of dihydroisolaurolene, which has been determined by Dr. W. H. Perkin, 

 Sen. 



' Bull. Soc. CUm., 1898 (iii), 19, 533. 

 « lUd., 1898 (iii), 19, 284. 



S2 



