Study 6.16 Chemistry in ionic liquids photoreduction

Case Study 6.16 Chemistry in ionic liquids - photoreduction 

2 Carbonyl Compounds Oxetane Formation (Paterno-Biichi Reaction) 

The attack of n,Jt excited carbonyl compounds on electron-rich or electron-poor alkenes can be qualitatively different.892 893 Electron-rich alkenes preferentially interact with the electrophilic half-filled n-orbital on the oxygen atom, which is perpendicular to 

The lowest excited singlet states of aliphatic aldehydes and ketones have lifetimes on the order of nanoseconds, but they can be trapped by alkenes in a diffusion-controlled bimolecular oxetane formation. According to a theoretical study, a C-atom attack mechanism is either a concerted process producing oxetane directly or it involves a C—C bonded transient singlet biradical intermediate that rapidly cyclizes.896 The O-atom attack, in contrast, represents a nonconcerted path, allowing conformational motion of the shortlived intermediate thereby formed. 

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