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S H g. of product is recovered, making the total yield 105-110 g. ((i-1 (>7 per cent of the theoretical amount).
1. All the chemicals used were from the Eastman Kodak ( ompany. The checkers used the Practical grade of ^-toluidine, which was distilled just before use.
2. The l> tolylthiourea may be isolated at this point, if desired, liy filtering and washing the solid residue with ether. The dried Ľnilid (172 g.) is a mixture of the urea and sodium sulfate. It is exlI'.u led will) 250 cc. of warm (50 (>()") water; the residual urea,
m.p. 188-189░, is completely soluble in alcohol. The yield is 139 g. (84 per cent of the theoretical amount).
3. The recovery is about 600 cc.; it may be used again without purification.
4. Treatment of the solution with Norite at this point does not give a product of any better quality.
5. If less alcohol is used, crystallization takes place during filtration.
6. The literature gives melting points ranging from 128░ to 142░, the higher value being for aminomethylbenzothiazole prepared via the hydrochloride (m.p. 250-253░). The submitters report that the product obtained above is unchanged in melting point after regeneration from the hydrochloride. By this treatment, however, the color is removed.
3. Methods of Preparation
2-Amino-6-methylbenzothiazole has been prepared by the action of cupric thiocyanate,1, 2' 3 or of chloramine and ammonium thiocyanate,4 on ^-toluidine; by the action of chlorine on di-^-tolylthiourea; 5 or of bromine on acetyldi-^-tolylthiourea;6 by treatment of />-tolylthiourea with halogens7 or acid halides. 8ĺ 9> 10, 11 ĺ12 2-Aminobenzothiazole has been prepared in
1 Kaufmann, Oehring, and Clauberg, Arch. Pharm. 266, 197 (1928). [C. A. 22 2166 (1928)].
2 Kaufmann and Kiichler, Ber. 67, 946 (1934).
3 Kaufmann, Ger. pat. 579,818 [C. A. 28, 1053 (1934)].
4 Likhosherstov and Petrov, J. Gen. Chem. (U.S.S.R.) 3, 759 (1933) [C. A. 28,
61. G. Farbenind. A-G., Fr. pat. 688,867 [C. A. 25, 968 (1931)].
6 Hunter and Jones, J. Chem. Soc. 1930, 2197.
7 Hunter, J. Chem. Soc. 1926, 1399.
8 Herz and Schubert, U. S. pat. 2,003,444 [C. A. 29, 4774 (1935)].
91. G. Farbenind. A-G., Brit. pat. 345,735 [C. A. 26, 1944 (1932)].
10 E. I. du Pont de Nemours and Company, Fr. pat. 727,410 [C. A. 26, 5103 (1932)].
11 Herz and Schubert, Ger pat. 537,105 [Frdl. 17, 615 (1932); C. A. 26, 1000 (1932)].
12 Schubert and Schiitz, Ger. pat. 604,639 [Frdl. 21, 227 (1934); C. A. 29, 819 (1935)].
excellent yield by the action of hydroxylamine upon benzothi-azole.13
3-AMINO-2-NAPHTHOIC ACID (2-Naphthoic Acid, 3-amino-)
^ˇ\˝ţ2 ZnCl2 ^/^co2H
Submitted by C. F. H. Allen and Alan Bell.
Checked by Nathan L. Drake, E. W. Reeve, and J. Van Hook.
An autoclave (Note 1) is charged successively with 600 cc. (').5 moles) of approximately 28 per cent aqueous ammonia, 78 g of zinc chloride (0.57 mole) (Notes 2 and 3), and 167 g. of 3-hydroxy-2-naphthoic acid (0.89 mole) (Note 4). The autoclave is dosed, and then, with continuous stirring or shaking (Note 5), │ I is gradually heated, so that, at the end of three hours, the temperature is 195░. This temperature is maintained for thirty-six hours; the pressure is about 400 lb. (Note 6). The autoclave is allowed to cool to room temperature, with continuous stirring nr shaking. The cover is removed, the solid is scraped off the walls, and the reaction mixture is transferred to a 5-1. flask. The autoclave is rinsed with two 700-cc. portions of water, which are in Med to the reaction mixture.
To the reaction mixture is added 660 g. of concentrated hydro-
< liloric acid (sp. gr. 1.18), and the suspension is boiled for-half an hour. It is then filtered, while hot, through a Buchner funnel. The residual cake is boiled again, for the same length of time, will) a mixture of 500 cc. of water and 30 cc. of concentrated hydrochloric acid, and then filtered as before.
The combined filtrates, on cooling, deposit the hydrochloride of the aminonaphthoic acid; this is filtered with suction and is
1,1 KkrniiPi Ann. 410, f>5 (1'╦9).
pressed as dry as possible. To obtain a second crop of the hydrochloride, the filtrate is heated to 85░, 500 g. of salt is added, and the solution is cooled.
The combined moist filter cakes are placed in a 5-1. flask with 1.3 1. of water, and, with stirring, sufficient 40 per cent sodium hydroxide solution is added to make the solution just alkaline to Clayton yellow paper (Note 7); about 110 cc. is required. The mixture is heated to 85░ and is filtered to remove a small amount of insoluble material. The filtrate is then made acid to Congo red by addition of concentrated hydrochloric acid (about 100 cc. of acid is required). The mixture is stirred for fifteen minutes, and then enough 10 per cent sodium acetate solution is added so that Congo red paper is no longer turned blue; the amount needed depends on the acidity; usually about 15 cc. is sufficient.