XXXII.—Studies on optically active carbimides. Part V. The aryl esters and the amides of l-menthylcarbamic acid

Robert Howson Pickard, William Oswald Littlebury
1907 Journal of the Chemical Society Transactions  
IN P a r t 11. (Trans., 1906, 89, 94) jt WRS shown that Z-menthylcarbimide reacts very readily with alcohols, forming stable esters of I-menthylcarbamic acid. The most striking property of these esters is the regularity exhibited by the molecular rotations i n various solvents ; for example, in chloroform, the molecular rotations approximate t o -160' and in pyridine to -175". It appeared desirable to investigate this point further, and therefore we have determined the rotations of eleven aryl
more » ... sters and eighteen amides of I-menthylcarbamic acid. The results may be sunimnrisecl a s follows : the approximately constant molecular rotation of -160' given in chloroform solution by, the alkyl esters is also given by the aryl esters, the amide, and also such monosubstituted amides of I-menthylcarbamic acid as were prepared from a primary aliphatic amine, whilst the mono-substituted amides containing a n aromatic radicle have a higher rotation. Contrasted with the results obtained in chloroform solution, the molecular rotations of these compounds i n pyridine solution are peculiar. Thus the aryl esters have molecular rotations approximating to -190°, that, is, higher than the rotations of the alkyl esters, which approximate to -175". This difference is doubtless due *to the influence of t h e aromatic radicles, which is again observable in the rotations of the amides ; for the mono-substituted 2-menthylcarbamides with aliphatic substituents give values for the molecular rotation in pyridine which approximate to -160' (the value also given in chloroform solution), whilst those with aromatic substituents give much higher values. It is noteworthy t h a t the two amides prepared from secondary amines, namely, diethylamine and piperidine, have comparatively high rotations in both solvents. The rotations of the amides have also been determined in absolute ethyl alcohol for the purpose of comparison with the rotations of the amides of d-butglcarbamic acid (Urban, Avch. Phavm., 1904, 242, 51). The effect of a varying substituent R in the amides of d-butylcarbamic acid, C,H,-NH*CO*NHR, is very much greater than in the amides of I-menthylcarbnmic acid. I n view of the similarity in the constitution of menthylamine and menthol, it is interesting to compare the regularities i n the molecular rotations i n chloroform solution of the compounds described below and the numerous menthyl esters of aliphatic and aromatic acids
doi:10.1039/ct9079100300 fatcat:qive55ub5rcqbdw4e6tdgyhwlu