# 1911 Encyclopædia Britannica/Thiazines

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​THIAZINES, in organic chemistry, a series of cyclic compounds containing a ring system of four carbon atoms, one nitrogen and one sulphur atom. These may be grouped in three ways, giving the following skeletal structures:-
Members of the first series have not as yet been isolated. Derivatives of the second type have been obtained by A. Luchmann (Ber. 1896, 29, p. 1429) by condensing γ-chlorbutylamine with carbon bisulphide or with mustard oils in the presence of caustic alkali; by M. Kahan (ibid., 1897, 30, p. 1321) on condensing bromhexylamine hydrobromide with thiobenzamide:
CH$_2$CH(CH$_3$)Br, HS > CH$_2$·CH(CH$_3$)·S
(CH$_3$)$_2$C·NH$_2$ HN:C·C$_6$H$_5$ (CH$_3$)$_2$C - N=======C·C$_6$H$_5$
Benzothiazines are obtained from ortho-aminobenzyl halides and thio-amides:
C$_6$H$_4$ CH$_2$Br CH$_2$·S
N==C·CH$_3$.
The most important thiazines are those derived from class III., thiodiphenylamine, C$_6$H$_4$N SC$_6$H$_4$, being the parent substance of the methylene blue series of dyestuffs. Thiodiphenylamine ​is obtained synthetically by heating sulphur with diphenylamine or by the condensation of ortho-aminothiophenol with pyrocatechin. It is a compound of neutral reaction. The first known dyestufi of this series was Lauth's violet, which was prepared by oxidizing paraphenylene diamine in acid solution in the presence of sulphur. By using dimethyl paraphenylene diamine in place of the simple diamine, methylene blue is obtained. The relationship of these substances to thiodiphenylamine was shown by A. Bernthsen, who, by nitration of thiodiphenylamine, obtained a dinitro-compound which on reduction was converted into the corresponding di-amino-derivative and this on oxidation yielded Lauth's violet. miaire (5th October 1795) he opposed those Thermidorians who wished to postpone the dissolution of the Convention. At the elections for the Corps Législatif he was elected by no less than thirty-two departments. It was only by the intervention of Boulay de la Meurthe that he escaped transportation after the coup d'état of 18 Fructidor (4th September 1797), and he then returned to the practice of his profession. The establishment of the consulate brought him back to public life. He was made prefect of the Gironde, and then member of the council of state, in which capacity he worked on the civil code. He at this time had Napoleon's confidence, and gave him wholehearted support. He did not entirely conceal his disapproval of the foundation of the Legion of
H NH N c.H.I'sHc.H.-> N01-CsH=<1; CeHa ~ N02 -> NH2- c.H.< S >c.H.-NH.-> HN:Col-Ia(S>c.H.-Nm Honour, of the Coucordat and of the Methylene blue is the most important of all blue basic dyes and is put on the market frequently in the form of its zinc chloride double salt, which is soluble in water. Acid oxidants in dilute aqueous solution convert it into methylene azure. See further A. Bernthsen, Ann., 230, p. 73; 251, p. 1; German Patents 45839 (1887); 47374 (1888). For a discussion as to the constitution of these dyestuffs, whether they are quaternary ammonium salts or thionium salts, see A. Hantzsch, Bef., 1906, 39, pp. 153, 1365; F. Kehrmann, ibid., 1906, 39, p. 914.