Nef reaction

Nef reaction
Named after	John Ulric Nef
Reaction type	Substitution reaction
Identifiers
Organic Chemistry Portal	nef-reaction
RSC ontology ID	RXNO:0000157

The Nef reaction is an organic reaction describing the acid hydrolysis of a salt of a primary or secondary nitroalkane (1) to an aldehyde or a ketone (3) and nitrous oxide (4). The reaction has been the subject of several literature reviews.

The reaction was reported in 1894 by the chemist John Ulric Nef, who treated the sodium salt of nitroethane with sulfuric acid resulting in an 85–89% yield of nitrous oxide and at least 70% yield of acetaldehyde. However, the reaction was pioneered a year earlier in 1893 by Konovalov, who converted the potassium salt of 1-phenylnitroethane with sulfuric acid to acetophenone.

The Nef reaction should not be confused with the Nef synthesis.

The reaction mechanism starting from the nitronate salt as the resonance structures 1a and 1b is depicted below:

The salt is protonated forming the nitronic acid 2 (in some cases these nitronates have been isolated) and once more to the iminium ion 3. This intermediate is attacked by water in a nucleophilic addition forming 4 which loses a proton and then water to the 1-nitroso-alkanol 5 which is believed to be responsible for the deep-blue color of the reaction mixture in many Nef reactions. This intermediate rearranges to hyponitrous acid 6 (forming nitrous oxide 6c through 6b) and the oxonium ion 7 which loses a proton to form the carbonyl compound.

...
Wikipedia