Experiments on the Preparation of Aminohydroxynaphthoic Acids

Syme, A. C (1940) Experiments on the Preparation of Aminohydroxynaphthoic Acids. PhD thesis, University of Glasgow.

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Some suggested methods for the preparation of aminohydroxynaphthoic acids have been investigated. The main part of the research was devoted to the preparation of those having the -NH2 group in the 2-position, and the particular one desired was the 2-amino-5-hydroxy-7-naphthoic acid. The scheme, outlined on pages 13 and 14, shows that the -OH group was to be introduced by sulphonation and subsequent alkali fusion of 2:7-aminonaphthoic acid. Consequently the first consideration was the preparation of 2:7-aminonaphthoic acid. The formation of 2:7-aminonaphthonitrile by replacement of -SO3H by -CN by the dry distillation of 2:7-aminonaphthalene sulphonic acid with KCN and K4Fe(CN)6 gave very poor yields, insufficient for the subsequent series of reactions, while fusion with KCN under pressure eliminated the -SO3H group. The diazotisation of 2:7-aminonaphthol was successfully accomplished by the usual Greiss reaction in the presence of a large excess of HCl; also after the method of Hodgson & Walker, and that of Schoutissen, but attempts to form the 2:7-cyanonaphthol by the Sandmeyer reaction and various modifications of same failed due to the preference of the diazo compound to couple with itself. The diazotisation of 2:7-diaminonaphthalene was accomplished using a modification of the method of Schoutissen, but attempts to form the 2:7-aminonaphthonitrile failed. 2:7-Aminonaphthoic acid was synthesised from 2:7-aminonaphthalene sulphonic acid by the series of reactions outlined on page 82 and described on pages 120-136, and successfully sulphonated but the yield of sulphonic acid was poor. The same result was obtained with chlorosulphuric acid. Sulphonation of the acetyl derivative gave excellent yields, but isomers were present and various attempts to separate them were unsuccessful, while conversion to the aminohydroxynaphthoic acids by alkali fusion yielded oxidation products. Estimation of the alpha-SO3H groups in the sulphonation mixture gave 60%. It would appear, judging from results on page 125, that about 40% of the sulphonic mixture contains the -SO3H group in the 6-position. The preparation of 1:2:7- and 1:2:6-aminohydroxynaphthoic acids was accomplished by method 1. They were obtained as the hydrochlorides since the free bases oxidise very rapidly in the air. The action of nitrous acid on 2:7- and 2:6-hydroxy-naphthoic acids gave highly coloured products containing no nitrogen. A table of properties is given on page 189.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1940
Depositing User: Enlighten Team
Unique ID: glathesis:1940-80219
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 02 Mar 2020 17:20
Last Modified: 02 Mar 2020 17:20
URI: https://theses.gla.ac.uk/id/eprint/80219

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