Para-Nitrosophenol

Beilstein Handbook Reference) AI3-19026 BRN 1856695 p-Chinonmonoxim CCRIS 4710 EINECS 203-251-6 HSDB 5362 Nitrosophenol NSC 3124 p-Nitrosophenol 4-Nitrosofenol 4-Nitrosophenol para-Nitrosophenol Phenol, 4-nitroso-... 

Phenol—is converted to para-nitrosophenol and then reduced and acetylated,... 

The theory that the catalysed nitration proceeds through nitrosation was supported by the isolation of some />-nitrosophenol from the interrupted nitration of phenol, and from the observation that the ortho.-para ratio (9 91) of strongly catalysed nitration under aqueous conditions was very similar to the corresponding ratio of formation of nitrosophenols in the absence of nitric acid. ... 

In reactions of A,A-dimethylaniline, care must be taken in the final isolation of the free p-nitrosoamine from its salt, since prolonged treatment with excessive alkali leads to the formation of p-nitrosophenol [21a]. By the way, the initial proof that the product of nitrosation is the para isomer was simply based on the observation that, after prolonged add hydrolysis of p-nitrosophenol, a product formed which had an odor that resembled that of 1,4-benzoquinone. It is to be hoped that more substantial structure proofs are used today. 

Phenol may be converted into a mixture of o- and p-nitrophenols (Expt 6.102) by reaction with dilute nitric acid the yield of p-nitrophenol is increased if a mixture of sodium nitrate and dilute sulphuric acid is employed. Upon steam distillation of the mixture of nitrophenols, the ortho isomer passes over in a substantially pure form the para isomer remains in the distillation flask, and can be readily isolated by extraction with hot 2 per cent hydrochloric acid. The mechanism of the substitution probably involves an electrophilic attack (cf. Section 6.2.1, p. 851) by a nitrosonium ion at a position either ortho or para to the activating hydroxyl group, to yield a mixture of o- and p-nitrosophenols, which are then oxidised by the nitric acid to the corresponding nitrophenols. The reaction depends upon the presence in the nitric acid of traces of nitrous acid which serve as the source of the nitrosonium ion. 

Thus, as shown in Scheme 8.37, nitrous acid (FlNOi) produced in situ from sodium nitrite (NaN02) and sulfuric acid (H2SO4) reacts with phenol in aqueous solution to produce nitrosophenol. Substitution occurs para to the hydroxyl. 

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