Isomerization reactions of olefinic hydrocarbons in presence of aluminosilicates communication 2

Summary

• 1. In presence of an aluminosilicate catalyst at 250°, acyclic and cyclic olefin hydrocarbons undergo considerable structural changes, which are readily explained by means of a mechanism scheme in which the intermediate formation of cyclopropane derivatives is postulated. The following are the most characteristic types of isomeric transformations:1) isomerization of normal olefins Into monoalkylalkenes in which the alkyl group stands at the double bond; 2) formation of dialkylalkenes from monoalkylalkenes in which the alkyl side group is well removed from the double bond; 3) breakdown of a grouping at a quaternary carbon atom, except in those cases in which, in addition to a quaternary carbon, there is a tertiary carbon at the double bond; 4) in the isomerization of C_T (and higher) cycloalkenes, a mixture of two parts of six-membered and one part of five -membered naphthenes informed; 5) in hydrocarbons having a primary-secondary double bond; migration of the double bend so as to form unsymmetrically substituted ethylene derivatives readily occurs; 6) reduction in the number of carbon atoms in alkyl side groups occurs.

• 2. The overall result of the catalytic transformations of olefinic hydrocarbons in presence of aluminosilicate should be regarded as the summative effect of isomerization and hydrogen-redistribution processes, and the unsaturated hydrocarbons that are mainly formed are those which have the least tendency to undergo isomerization under the experimental conditions and which are readily saturated at a later stage owing to the redistribution of hydrogen. The most characteristic forms of saturated C₂-C₂ hydrocarbons obtained at 250° we consider to be: 2-methylalkanes; 2,3-, 2,4-, and 2,5-dimethylalkanes; methylcyclopentane; methylcyclohexane; and also 1,3-dimethylcyeiopentane and 1,4-dimethylcyclohexane.