Dichloroaniline and 2,6 Dibromoaniline

5-Dichlorosulfanilamide. In a 2-1. round-bottomed flask, fitted with a two-holed stopper carrying a mechanical stirrer and a thermometer, are placed 50 g. (0.29 mole) of sulfanilamide and 500 ml. of water. About 50 ml. of a 500-ml. portion (approximately 6 moles) of pure concentrated hydrochloric acid is added, and the mixture is stirred until a clear solution results (Note 1). The remainder of the 500 ml. of hydrochloric acid is then added. If the internal temperature does not rise to 45°, the stirred solution should be warmed gently with a free flame until this temperature is reached. At this point 65 g. (59 ml., 0.58 mole) of 30% hydrogen peroxide (sp. gr. 1.108) is added and rapid stirring is initiated (Note 2). The heat of reaction causes a progressively faster rise in temperature. After 5 minutes the solution fills with a white precipitate which increases rapidly in amount and becomes delicately colored. When the temperature has reached 60°, about 10 minutes after adding the peroxide (Note 3), any further rise is preferably prevented by judicious cooling (Note 4). The reaction is allowed to proceed for 15 

5-Dibromo sulfanilamide. The bromination of sulfanilamide is carried out in much the same way as the chlorination. The stirrer must be more efficient (Note 9) a glass stirrer with two sets of blades is satisfactory if run at high speed. Fifty grams (0.29 mole) of sulfanilamide is dissolved in a mixture of 850 ml. of water (Note 9) and 100 ml. (0.68 mole) of 40% hydro-bromic acid (Note 10). The solution is heated as above, but to 70-75°, and 65 g. (59 ml., 0.58 mole) of 30% hydrogen peroxide is added (Notes 2 and 11). A precipitate settles in 2 to 3 minutes, and the solution becomes yellow. The heat of reaction causes the internal temperature to rise without further application of heat to a maximum of 85-90° after 10 minutes by the end of the reaction time the temperature will have fallen to about 

70° (Note 12). After a total reaction time of 30 minutes (Note 13), during which the mixture has become almost solid and is very difficult to stir, the material is filtered hot (Note 14). The yield of 3,5-dibromosulfaniIamide is 85-90 g. (90-94%), and the crude tan product (Note 15) melts over a range of 1-2° in the region 230-237° (Note 16). 

6-Dibromoaniline. In a 2-1. flask, equipped with a two-holed stopper carrying an exit tube to a condenser and an entrance tube for steam, 50 g. of crude 3,5-dibromosulfanilamide (Notes 17 and 18) and 250 ml. (5 ml./g.) of 70% sulfuric acid are heated in an oil bath when the temperature of the bath reaches 175-180°, steam is passed rapidly through the mixture (Note 19). The hydrolysis is continued in this way for 2 hours small amounts of the dibromoaniline distil (Note 20). The bath is then allowed to cool to 105-110°. At this temperature the main mass of the product is steam-distilled. The slightly colored 2,6-dibromoaniline melts at 84-86° and weighs 25-30 g. (66-79% based on 3,5-dibromosulfanilamide) (Note 21). It may be purified by recrystallization from 70% alcohol (7 ml./g.) after recrystallization the product is obtained as long colorless needles which melt at 87-88°. The recovery is 85-90%. 

Solution of sulfanilamide is more readily obtained in this way than by treating the amide at once with 6 N acid for, in the latter case, the salt precipitates at first and redissolves only slowly. If acid stronger than 6 N is used, a larger volume is required to dissolve the sulfanilamide hydrochloride, and the product is partly held in solution as dichlorosulfanilamidc hydrochloride unless the solution is diluted. If 4 A acid is used, the reaction is much slower without any worthwhile decrease in the color of the product. 

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Diaz et al. [583] recently studied the synthesis and properties, including spectroscopy and morphology, of dihalogenated P(ANi) s, specifically poly((2,5)/(2,3)/(3,5)-dichloroaniline) and poly((2,5)/(2,6)-dibromoaniline). Chemical synthesis using Cu perchlorate, K dichromate and K permanganate was employed. 

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