AbstractThe equilibria in the isomerisation of the methylcyclohexenes and methylenecyclohexane have been investigated in the temperature range of 413 to 523 K. ΔrHand ΔrShave been calculated from the experimental data for the following equilibria: methylenecyclohexane ⇄ 1‐methylcyclohexene, 3‐methylcyclohexene ⇄ 1‐methylcyclohexene and 4‐methylcyclohexene ⇄ 1‐methylcyclohexene. The resulting values for ΔrHand ΔrSare respectively: 7.3 ± 1.7, 7.6 ± 0.5, and 6.7 ± 0.4 kJ mol−1and −15.9 ± 0.3, 1.0 ± 1.6 and 1.5 ± 1.4 J mol−1K−1. These data are compared with values cal