Arteleo Chemistry Journal

The Bucherer Reaction

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Naphthols and the corresponding naphthylamines are interconvertible in aqueous media containing sulphite or bisulphite ion at elevated temperatures23. Thus naphthols may be converted to naphthylamines by reaction with ammonia and ammonium sulphite in aqueous solution, usually in the temperature range 90-150°; the corresponding dinaphthylamine is sometimes obtained as a byproduct (reaction 15). MonoaLkylamines and dialkylamines similarly

OH NH2

give the alkylamino- and dialkylaminonaphthalenes, though higher temperatures are normally required. Naphthols also react with aryl-amines to give the arylaminonaphthalene, 1-naphthols reacting less readily than 2-naphthols. Similar cases have also been noted with arylamines (reaction 16).

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Bisulphite addition compounds of naphthols have been isolated in a number of cases, and for a considerable time these were formulated as derivatives of the ketonic form of the naphthol. Until recently, the generally accepted reaction scheme was (17) with the naphthol possibly reacting in the keto form. This overall equilibrium picture

was consistent with the results of a systematic kinetic study of the reaction conducted with a number of naphthol and naphthylamine

The structures of the intermediate addition compounds have been reconsidered in the light of their physical and chemical properties, and the compounds from 1- and 2-naphthols are now formulated as tetral-1-one-3-sulphonates (3) and tetral-2-one-4-sulphonates (4) respectively25,26. Discussion of this evidence is beyond the scope of the

present chapter but it is interesting to note that a new synthesis of 1-naphthol-3-sulphonic acids has emerged from this work. The scheme for the interconversion of naphthols and naphthylamines may be summarised by reaction (18), with the possibility of ketimine and enamine intermediates, except in the special case of reactions involving dialkylamines, when only an enamine intermediate is possible. Amine exchange reactions of 1- and 2-naphthylamines with an amine R2NH are likely to involve further intermediates of types 5 and 6 respectively, formed by addition of the amine R2NH to the intermediate ketimine or enamine.