The Nitrous Acid-catalysed Nitration of Phenol

DOI: 10.1039/P29850000467

Source and publish data:

Journal of the Chemical Society. Perkin transactions II p. 467 - 472 (1985)

Update date:2022-08-18

Topics:

Authors:

Al-Obaidi, Usama

Moodie, Roy B.

Read Full Text PDF DownLoad Join now for total 90,000,000 free articles

Article abstract of DOI:10.1039/P29850000467

The reaction of phenol with nitrous acid (10E-4M < III> < 10E-2M) and nitric acid (10E-3M < V> < 0.3M) in aqueous sulphuric acid (19-45percent H2SO4) at 25 deg C gives rise to p-nitrophenol by a nitrosation-oxidation pathway, and concurrently to a 57:43 mixture of o- and p-nitrophenol by catalysed nitration.The latter reaction is the major one, and is first-order in phenol with a first-order rate coefficient given by III>V>/(xIII> + yV>).The x and y are constants for a given concentration of sulphuric acid.The dependence of x and y upon acidity, and comparison of the reactivity of phenol with that of hexadeuteriophenol and anisole, leads to a proposed mechanism for catalysed nitration.In this there is pre-equilibrium formation, from phenol and N^III, of an intermediate with the formula PhONO.This gives rise to a phenoxyl radical and nitric oxide, a step which is rate limiting when the rate is fully enhanced by V>.Nitric oxide is reversibly oxidised by N^V to give NO2 and N^III.Reaction is completed by combination of the phenoxyl radical and NO2, in a step which is rate limiting when the rate is fully enhanced by III>.