Substituent Effects in Heterogeneous Catalysis. VI. Competitive Hydrogenation of Methylenecyclohexane and 2-Methyl-methylenecyclohexane over Platinum Group Metals

Methylenecyclohexane and its 2-methyl derivative were hydrogenated competitively in cyclohexane at 30 °C over platinum group metals. The methyl derivative was less reactive than the unsubstituted olefin on all the metal catalysts used. The reactivity of the methyl derivative relative to the unsubstituted olefin was not much different in going from one catalyst to another. However, Pd was unique in its very high activity for double bond migration. MINDO/2 calculations have revealed that the olefinic double bonds of the substituted and unsubstituted olefins are essentially identical in bond order but somewhat different in charge density. The observed methyl substituent effect is compared with that observed previously in hydrogenation of cyclohexanone and its 2-methyl derivative.