Studies on the Autoxidation of the Isomeric n-Octenes
The products of autoxidation of the positionally and sterically isomeric n-octenes were analyzed by gaschromatography. 22–37% of the gaschromatographically detected compounds were epoxides, 2–9% were products of oxidative cleavage of the CC-double bond, and 50–70% were allylic oxidation products. Independently of the stereochemistry of the starting olefins mixtures of the corresponding cis- and trans-epoxides were always formed; in the oxidation products of cisoctenes more cis-epoxides are present than in the oxidation products of trans-octenes. The composition of the octenol mixtures, obtained by preparative gaschromatographic isolation from the sodium sulphite reduction products of the oxidates, could be determined by 13C-n.m.r. analysis. All expected positional isomers are formed. The trans-octenes almost exclusively yield the trans-octenols; from the cis-octenes the octenols with the double bond in the original position are formed as mixtures of the corresponding cis- and trans-isomers, but the octenols with shifted double bonds almost exclusively are present in their transforms.
The stereochemical results are discussed on the basis of the lifetime and the conformational or configurational stability of the intermediate radicals.
In connection with the 13C-n.m.r.-investigation of the reaction products increments for the shift of 13C-signals by introduction of hydroperoxy, hydroxy, and carbonyl groups in allylic position of olefins were derived.