SINGLET OXYGEN REACTIONS WITH 2,7‐DIMETHYL‐2,6‐OCTADIENE

Abstract
Abstract— Results concerning Rose Bengal sensitized photoxidation of 2,7‐dimethyl‐2,6‐octadiene (A) are discussed. This diolefin may be considered as a model molecule of polyisoprene of polymerization number two with 1,4‐4,1 addition mode.All the mono‐ and dihydroperoxides apt to occur are actually obtained. One of the occurring hydroperoxides, 2,7‐dimethyl‐dihydroperoxy‐3,5‐octadiene, which has the structure of a conjugated diene, does not lead to an endoperoxide. This is contrary to Kaplan and Kelleher's hypothesis. On the other hand, no trihydroperoxide forms as a result of further addition of singlet oxygen (1O2).A complete kinetic study has allowed us to determine the rate constants of all the reactions which take place. The reactivity of (A) is twice that of 2‐methyl‐2‐pentene and the addition of 1O2 to one of the double bonds of (A) induces deactivation of the remaining double bond.