Carbonyl compounds Norrish type I reaction

In general, the n,Jt excited ketones undergo much faster cleavage than those with a lowest 7t,7t excited state, because the O-orbital of a bond being cleaved overlaps with the half-vacant n-orbital on the oxygen atom.905,911,919 The cleavage rate constant of the n,jt triplet excited benzyl phenyl ketone (PhCH2COPh) is, for example, more than three orders 

Case Study 6.19 Photochemistry in crystals - solid-to-solid photoreaction 

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