Norrish Reaction - Norrish II

Norrish II

A Norrish type II reaction is the photochemical intramolecular abstraction of a γ-hydrogen (which is a hydrogen atom three carbon positions removed from the carbonyl group) by the excited carbonyl compound to produce a 1,4-biradical as a primary photoproduct (IUPAC definition).

Secondary reaction are either intramolecular recombination of the two radicals to a cyclobutane compound (path A) or fragmentation to an enol and an alkene.

The reaction was first reported in 1937 by Ronald George Wreyford Norrish.

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