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Encyclopedia Britannica - Main :: I27-INV |
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IMIDAZOLES, or GLYOXALINES , organic chemical compounds CH=CH containing the ring system
first prepared by H. Debus(Ann. 1858, 107, p. 254) by the action of ammonia on glyoxal, 2C2H202+2NH3=C3I-I4N2+H2CO2+2H20. The compounds of this series may be prepared by the condensation of ortho-diketones with ammonia and aldehydes RC-N RCOCORd-2NH,+R'CHO=3H2O+ fl ~CR ; R.C-NHS from thioimidazolones by oxidation with dilute nitric acid (W. Marckwald, Ber., 1892, 25, p. 2361); by distillation of hydrobenzamide and similarly constituted bodies; and by the action of phosphorus pentachloride on symmetrical dimethyloxamide, a methylchlorglyoxaline being formed (O. Wallach, Ann., 1877, 181, P. joo). The glyoxalines are basic in character , and the imide hydrogen is replaceable by metals and alkyl groups They are stable towards reducing agents, and acidyl groups are only introduced with difficulty.Irnidazole (glyoxaline), C3H4N2, crystallizes in thick prisms which melt at 88-89 C. and boil at 2J3 C., and are readily soluble in alcohol and in water. It is unaffected by chromic acid, but potassium pe-manganate oxidizes it to formic acid. It forms salts with acids. CeH;C-N Lophine (triphenylglyoxaline), II 2CC6Hy, is formed CbHSC-NH by the dry distillation of hydrobenzamide, or by saturating an alcoholic solution of benzil and benzaldehyde (at a temperature of 4o C.) with ammonia. It crystallizes in needles which melt at 275. C. It is a weak base. When heated to 300 C. with hydriodic acid and hydrochloric acid, in the presence of some red phosphorus, it yields benzoic acid. The keto-glyoxalines are known as imidazolones and are prepared by the action of acids on acetalyl thioureas (W. Marckwald, Ber., 1892, 25, P. 2357). Benzimidazole, C6H4\ NH >CH, is the simplest representative of the benzoglyoxalines and is prepared by the condensation of formic acid with ortho-phenylene diamine. It forms rhombic crystals which melt at 17o C. It is basic in character , and on oxidation with potassium permanganate yields aHOOCC-N small amount of glyoxaline dicarboxylic acid, II HOOCC-NH' (E. Bamberger, Ann., 1893, 273, p. 338). End of Article: IMIDAZOLES, or GLYOXALINES If you wish, you can link directly to this article.
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