Norrish Type I photoreaction

α-Cleavage of an excited carbonyl compound leading to an acyl-alkyl radical pair (from an acyclic carbonyl compound) or an acyl-alkyl diradical (from a cyclic carbonyl compound) as a primary photoproduct.
Notes:
  1. An example is:
    N04219
  2. Decarbonylation of the primary diradical formed from cyclic carbonyl compounds and subsequent recombination of the biradical afford very interesting cyclic compounds.
Source:
PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 375