Hydroperoxy cyclic peroxide mechanism

Porter et al, in two significant papers, have offered a unified mechanism of polyene autoxidation. This seeks to account for the various products obtained particularly from linoleic acid and from arachidonic acid (six hydroperoxides with one E double bond, six hydroperoxides with two E double bonds, and four hydroperoxy cyclic peroxides). The serial cyclisation of peroxy radicals observed with (51) is interesting in that the 1,5-diene units give rise to six-membered cyclic peroxides whilst the 1,4-diene units in natural... 

As an example, the formation of 1,2-dioxanes from 12-hydroperoxyoctadeca-9,13,15-trienoic acid derived from hnolenic acid is shown in Figure 3.35.1,2-Dioxanes are unstable compounds and decompose to low molecular weight flavour-active products. For example, 10-hydroperoxy-9,12-peroxyoctadeca-13,15-dienoic acid is decomposed into octa-3,5-dien-2-one. The mechanism of formation of 1,2-dioxolanes, cyclic peroxides and cycloendoperox-ides from 13-hydroperoxyoctadeca-9,ll,15-trienoic acid is shown in Figure 3.36. Peroxohydroperoxides of the 1,2-dioxolane type are considered to be the main precursors of toxic malondialdehyde (see Section 3.8.1.12.1). 

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