Preparation of 3,3′-benzidinedicarboxylic acid
A solution is made of 33.4 grams (0.2 mole) of pure o-nitrobenzoic acid in 120 ml. 40% sodium hydroxide solution and 40 ml. water, by heating to 100°. Zinc dust is added to this solution, in small portions with vigorous stirring, at such a rate that the temperature of the solution stays at 100-105° without external heating, continuing the addition until the originally deep yellowish brown solution is completely decolorized. About 40-50 grams of zinc dust is required, depending on its quality, and the addition requires about 15 minutes. As soon as the solution becomes colorless, 600 ml. hot water is added, and the excess zinc dust is filtered off and washed with hot water. The filtrate is treated with 20 ml. 2 N acetic acid and a few drops of sodium bisulfite solution (to prevent oxidation), and then 140 ml. of concentrated hydrochloric acid is added dropwise with good stirring. At this point, the solution should be strongly acid to litmus, but not to Congo red, so that rearrangement does not occur. (The acetic acid added earlier facilitates attainment of the correct acidity.) A filtered test portion of the solution should give no precipitate on addition of acetic acid, and additional acid is added if necessary. The solution is then cooled and the 2,2′-(hydrazine-1,2-diyl)dibenzoic acid, which separates in a crystalline, easily filterable form, is filtered off with suction and washed thoroughly with cold water. The pale brownish yellow filter cake, weighing about 50 grams, is stirred with 80 ml. water to form a uniform paste; 60 ml. of concentrated hydrochloric acid is added, and the mixture is heated at 95-100° for 30 minutes, maintaining the volume by addition of water. When the material has all dissolved except for a small black residue, the resulting solution is filtered hot and the residue washed with a hot mixture of 15 ml. concentrated hydrochloric acid and 30 ml. water. The violet colored filtrate is again heated to 70-80° and neutralized, with stirring, with ammonia (50 to 60 ml. 25 % solution) to the point where the acid reaction to Congo red disappears. The precipitation is then completed by the addition of a solution of 30 grams of crystalline sodium acetate in 70 ml. water. A filtered test portion should give no further precipitate with either acetic acid or sodium acetate. The precipitated 3,3′-benzidinedicarboxylic acid is filtered from the warm solution, washed thoroughly with warm water, and dried. The yield is about 26 grams of pale greenish gray product, or about 92 % of the theoretical amount.
The fundamental processes of dye chemistry, by H. E. Fierz-David, 164-165, 1949
2130-56-5, 3,3′-Benzidinedicarboxylic acid, Benzidine-3,3′-dicarboxylic acid, 5,5′-Bianthranilic acid, 5,5′-Dianthranilic acid, 3,3′-DICARBOXYBENZIDINE, HSDB 2738, Benzidine-M,M’-dicarboxylic acid, 2-amino-5-(4-amino-3-carboxyphenyl)benzoic acid, EINECS 218-348-9, Kwas benzydynodwukaroksylowy [Polish], BRN 2815505, 4,4′-Diamino-3,3′-biphenyldicarboxylic acid, 4,4′-diaminobiphenyl-3,3′-dicarboxylic acid, 3,3′-Biphenyldicarboxylic acid, 4,4′-diamino-, (1,1′-Biphenyl)-3,3′-dicarboxylic acid, 4,4′-diamino-, [1,1′-Biphenyl]-3,3′-dicarboxylic acid, 4,4′-diamino-, Kwas benzydynodwukaroksylowy, UNII-PLU8S18T9F, PLU8S18T9F, Oprea1_205130, CBDivE_004675, MLS000703166, SCHEMBL352643, AC1L280U, CHEMBL1584156, STOCK1N-02238, CTK1A7543, MolPort-001-932-305, HMS2743C23, ZINC192342, AKOS022507511, CD-1128, MCULE-4830898032, BENZIDINE-3 3-DICARBOXYLIC ACID, NCGC00245477-01, BAS 00431407, LS-44306, OR062551, OR241958, SMR000273630, 4,4-Diaminobiphenyl-3,3-dicarboxylic acid, ST50979172, 4,4′-Diamino-biphenyl-3,3′-dicarboxylic acid, 2-14-00-00345 (Beilstein Handbook Reference), 4,4′-DIAMINOBIPHENYL-3,3′-DICARBOXYLICACID, 3B1-003012, [1,1′-Biphenyl]-3,3′-dicarboxylicacid, 4,4′-diamino-, 78020-20-9