cis‐trans isomerization in polyisoprenes. Part VII. Double bond movement during the isomerization of natural rubber and related olefins

Abstract When trans‐3‐methylpent‐2‐ene or trans‐3‐methylhex‐3‐ene is treated with butadiene sulfone, thiolbenzoic acid, and dibenzoyl disulfide under anaerobic conditions, the olefin undergoes only cis—trans isomerization. However, similar reactions in the presence of oxygen or peroxides also cause changes in the position of the double bond. The latter structural modification is probably caused by acidic compounds formed by oxidation of the isomerization reagents. With natural rubber the nonrubber substances prevent movement of the double bond, and cis–trans isomerization is the sole change, even when the reaction with sulfur dioxide is carried out under aerobic conditions.