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 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.
Note that formation of the nitronate salt from the nitro compound requires an alpha hydrogen atom and therefore the reaction fails with tertiary nitro compounds.
The Nef reaction is frequently encountered in organic synthesis. It has been applied in carbohydrate chemistry as a chain-extension method for aldoses for example in the isotope labeling of C14-D-mannose and C14-D-glucose from D-arabinose and C14-nitromethane (the first step here is a Henry reaction):
The opposite reaction is the Wohl degradation.
- The NEF Reaction Wayland E. Noland Chem. Rev. 1955, 55(1), 137–55. (Review, doi:10.1021/cr50001a003)
- Pinnick, H. W. Org. React. 1990, 38, 655–792. (Review)
- Grierson, D. S.; Husson, H.-P. Comp. Org. Syn. 1991, 6, 937–44. (Review)
- Nef, J. U. Liebigs Ann. Chem. 1894, 280.
- Konovalov.,: J. Russ. Phys. Chem. Soc. 2 1893, 6(I), 509.
- A convenient synthesis of γ-functionalized cyclopentenones Nour Lahmar, Taïcir Ben Ayed , Moncef Bellassoued and Hassen Amri Beilstein Journal of Organic Chemistry 2005, 1:11 doi:10.1186/1860-5397-1-11
- McMurry, J. E.; Melton, J. Organic Syntheses, Coll. Vol. 6, p.648 (1988); Vol. 56, p.36 (1977). (Article)
- Miyashita, M.; Yanami, T.; Yoshikoshi, A. Organic Syntheses, Coll. Vol. 7, p.414 (1990); Vol. 60, p.117 (1981). (Article)
- Ceccherelli, P.; Curini, M.; Marcotullio, M. C.; Epifano, F.; Rosati, O. Synth. Commun. 1998, 28, 3057–64.