Hydrochloric Acid → 2-[(5-Chloro-2-methoxyphenyl)AZO]-1H-imidazole

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Reaction Steps

An example of preparing the azo compound may be illustrated as follows: To 50 parts by weight of water are added 5.1 parts by weight of 4-chloro-2-aminoanisole and 7.6 parts by weight of 35% hydrochloric acid, and a mixture of 2.2 parts by weight of sodium nitrate and 15 parts by weight of water is added thereto at 0°-5° C. The resulting mixture is stirred for 1 hour for the completion of diazotation. The first reaction mixture is then added at 0°-5° C. to a solution of 20.4 parts by weight of imidazole, 1.7 parts by weight of sodium hydroxide and 2.5 parts by weight of sodium acetate in 150 parts by weight of water. Stirring of the mixture for 1 hour can allow the diazonium salt to effect the coupling with imidazole, thereby precipitating a yellow-orange product. The product is then filtered, washed with water and then dried at 60° C. to provide 7.6 parts by weight of the crude azo compound. This crude azo compound (7 parts by weight) is recrystallized from n-propylalcohol to provide 7.6 parts by weight of pure 2-[(2-methoxy-5-chlorophenyl)azo]-1H-imidazole, having a melting point of 205° C. (decomposed), when measured in accordance with the designation of the Japanese Pharmacopoeia. It has a maximum ultraviolet absorption peak (λmax) at 384 mμ and its elementary analysis indicates as follows:

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