Preparation of 2,2′-dinitrobenzidine
To 56 g of pure benzidine sulphate 600 g of pure conc. sulphuric acid are added and the mixture well stirred. Solution is completed by heating up to 60° C if necessary. The solution is cooled down to about 10° C, but not lower, and 40 g potassium nitrate slowly added. After several hours’ stirring the solution is poured into about 2 litres of cold water and the 2,2′-dinitrobenzidine sulphate, which is precipitated, filtered off and washed with a little water. The 2,2′-dinitrobenzidine sulphate is then made into a cream with hot water and sodium hydroxide solution added until an alkaline reaction is given to phenolphthalein. The free base is then filtered off, washed with water, and recrystallised from water or from alcohol. Yellow leaflets, m.p. 214° C.
Systematic organic chemistry, by W. M. Cumming, 128, 1937.
2,2′-Dinitrobenzidine, CCRIS 5360, 5855-71-0, AC1NX4AQ, SCHEMBL153657, CTK5A8511, 2,2′-Dinitro-4,4′-biphenyldiamine, OR174584, SY027146, 4-(4-amino-2-nitrophenyl)-3-nitroaniline, LS-188363, [1,1′-Biphenyl]-4,4′-diamine,2,2′-dinitro-