Hydrogen reaction 4- triplet acetone

The quantum yields for oxetane formation have not been determined in every case, and only a few relative rate constants are known. The reactivities of singlet and triplet states of alkyl ketones are very nearly equal in attack on electron rich olefins. 72> However, acetone singlets are about an order of magnitude more reactive in nucleophilic attack on electron-deficient olefins. 61 > Oxetane formation is competitive with a-cleavage, hydrogen abstraction and energy-transfer reactions 60 64> so the absolute rates must be reasonably high. Aryl aldehydes and ketones add to olefins with lower quantum yields, 66> and 3n-n states are particularly unreactive. 76>... 

Sunlight irradiation (solar photochemical synthesis) of 1,4-naphthoquinone (27) in the presence of aldehyde (28) in a mixture of -butanol and acetone gives a good yield of the corresponding acyl hydroquinone (29) through the abstraction of the formyl hydrogen atom of aldehyde by the excited triplet biradical derived from 1,4-naphthoquinone, followed by the reaction of the acyl radical with 1,4-naphthoquinone (eq. 12.7). Here,... 

The relative reactivities of n,n singlets in hydrogen abstraction reactions has not yet been defined as precisely as for n,n triplets. There is little doubt that n,n singlets do abstract hydrogen atoms, since the unquenchable type II cycli-zation of compounds such as cyclohexenyl acetone involve allylic rearrangement 89,90). 

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