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Autoxidation is oxidation of a substance by molecular oxygen, commonly proceeding through a self-propagating free radical chain in organic materials. The name does not mean that initiation is unnecessary. Light, existing peroxides or other radical sources can start a chain, and changes in initiation can alter the observed rate.

A basic hydrocarbon propagation scheme writes the substrate as $\mathrm{RH}$:A peroxyl radical is converted into a hydroperoxide while generating a new carbon-centered radical. The two-step cycle consumes substrate and oxygen but regenerates a chain carrier. Radical–radical reactions can terminate chains; hydroperoxide decomposition can create further initiating species.

An original limiting kinetic model assumes abundant oxygen, approximately constant substrate concentration and termination dominated by pairs of peroxyl radicals. If initiation supplies radicals at rate $R_i$ and termination removes them at $2k_t{P}^2$, the steady radical concentration isQuadrupling $R_i$ then doubles the propagation rate rather than quadrupling it. This scaling follows from the stated balance; it need not hold when oxygen delivery, changing substrate or other termination pathways control the experiment.

A motivating modern apparatus is the inhibited autoxidation assay. A primary method co-oxidizes a hydrocarbon substrate with a BODIPY-based signal carrier and monitors progress with a visible-light spectrophotometer. Comparing inhibited and uninhibited traces tests radical trapping while distinguishing reaction rate from trapping capacity.^[ref]

A reduced signal slope can reflect chemical inhibition or inadequate oxygen supply, so controls for oxygen-limited autoxidation, probe response and matched initiation matter. The chain mechanism helps explain why excluding oxygen, intercepting radicals and changing peroxide decomposition can affect oxidation differently. An arbitrary antioxidant-assay signal alone does not establish product identity or a biological benefit.

Both free primary allylic alcohols undergo Sharpless asymmetric epoxidation. With slightly more than two equivalents of hydroperoxide, the expected fully oxidized product is the diepoxide, with both original C=C bonds converted to epoxides and both primary alcohols retained. The two central pre-existing stereocentres and their ether substituents are retained.

The stereochemical construction is unambiguous by applying the L-(+)-tartrate mnemonic separately at each end: orient that alkene horizontally with its CH${}_2$OH group at lower right, and deliver oxygen from the back face. In the source's original in-plane orientation this gives the left epoxide oxygen behind the plane and the right epoxide oxygen in front. The methyl and hydroxymethyl groups retain their original relative arrangement about each former double bond. One cannot simply draw both oxygens on the same face of the original extended chain: the two allylic-alcohol ends have opposite drawing orientations. titanium binding to each free hydroxyl directs oxygen transfer; the pre-existing stereocentres can create matched/mismatched rate differences, but the stated reagent control predicts the stereochemistry of both epoxidations. Molecular sieves maintain a dry active titanium–tartrate system.^[ref]

Manganese(III) removes one electron from the enol/enolate of H, and loss of its hydroxyl proton gives a carbon-centred radical at the tether-bearing alpha carbon of the resulting 1,3-dicarbonyl system. The enolic OH becomes the second carbonyl oxygen. This radical attacks the terminal CH${}_2$ of the tethered isopropenyl group, forming a new C–C bond and a six-membered ring. The residual radical is on the substituted carbon bearing methyl, which is more stable than the primary radical from the alternative regiochemical closure.

Dioxygen traps that radical as a peroxyl intermediate. reduction/proton transfer and O–O cleavage in the ensuing oxygenation/workup sequence give the new tertiary alcohol on the methyl-bearing carbon. The drawn net transformation specifies that oxygenated product, not a persistent hydroperoxide; individual electron/proton transfers require the reaction medium and workup and cannot be fixed uniquely from the abbreviated reagent line alone. The rigid cage and folded tether select the closure face and therefore the relative configuration of the new ring junction.

Finally the new hydroxyl oxygen attacks silicon of TBSCl, with imidazole assisting deprotonation and chloride departure, giving the tertiary silyl ether I. The hindered pre-existing hydroxyls remain as shown. Track the two key atom changes: the terminal alkene carbon becomes a methylene in the new ring, and the former substituted alkene carbon acquires oxygen and retains its methyl group. Calling the first step a two-electron aldol reaction would miss both the single-electron oxidant and the role of dioxygen.

Enantioselective oxygen transfer to an allylic alcohol using a titanium–tartrate complex and a hydroperoxide. With the alkene horizontal and its hydroxymethyl substituent at lower right, L-(+)-tartrate directs delivery from the back face and D-(−)-tartrate from the front face. Rotate a structure in its plane to apply the mnemonic; reflecting it changes its stereochemistry.