Geometrical Configuration of Dialkyl Naphthenes

Abstract

Present information on the spatial configuration of the dialky^l cyclopentanes and cyclohexanes is unsatisfactory. Zelinsky¹ concluded from the result of an asymmetric synthesis that the lower-boiling isomer of 1: 3-dimethylcyclohexane had the trans configuration, and following on this later workers have assigned the trans structure to the lower boiling isomers of naphthenes. Mousseron and Granger² carried out a more reliable asymmetric synthesis of 1: 3-dimethyl-cyclohexane and showed that the higher-boiling isomer was optically active and therefore of trans configuration. Chiurdoglu³ afterwards compared the relative rates of oxidation and bromination of the spatial isomers of various 1: 2-dialkylcyclopentanes, and found that the higher-boiling isomers possessed the greater reactivity. It was also found that trans l: 3-dimethylcyclohexane, as determined by Mousseron and Granger (loc. cit), and trans decalane reacted more rapidly with the above reagents than did their cis isomers. Chiurdoglu, therefore, concluded that the higher-boiling isomers of the 1: 2-dialkylcyclopentanes had the trans configuration. Pitzer and Beckett⁴, in a recent investigation of the theoretical and calculated entropies of the dimethylcyclohexanes, concluded that the nomenclature of the 1: 3-dimethylcyclohexanes should be reversed and that the higher-boiling isomer should be regarded as the trans isomer. This result is thus in agreement with that obtained by Mousseron and Granger (loc. cit.).