Nucleophilic Reactions at Tertiary Carbon. Part 1. The 1,2‐dimethyl‐1‐cyclohexyl cation

Stereoisomeric ion pairs are implicated as intermediates in the solvolysis of cis and trans ‐1‐chloro‐1,2‐dimethylcyclohexane, cis ‐ 4 and trans ‐ 4 , respectively. This follows from the rates and products of these stereoisomeric tertiary chlorides in 80% ethanol and 50% acetone. The composition of elimination and substitution products from cis ‐ 4 and trans ‐ 4 differs markedly and the differences are accentuated by silver ion. Furthermore, substitution products are formed with predominant inversion of configuration. The equilibrium constant for isomerization of cis ‐ 4 and trans ‐ 4 shows the latter to be more stable by 0.7 kcal/mol. Since the solvolysis rates of the chlorides are equal, the transition state for trans ‐ 4 is also more stable by 0.7 kcal. By inference the intermediates differ by a similar amount of energy which is ascribed to more efficient solvation of the trans ion pair 13 .