GB758395A - Condensation products of arylhydrazines - Google Patents

Abstract

Condensation products of arylhydrazines with reactants capable of reacting therewith, namely aldehydes, ketones, urea, cyanates and thiocyanates are prepared by heating an aqueous solution of the corresponding sodium or potassium arylhydrazine-N-sulphonate with sulphuric or preferably, hydrochloric or hydrobromic acid, neutralizing the excess of acid over one molar equivalent, e.g. with sodium or potassium hydroxides, adding the reactant (i.e. the substance with which condensation is to take place), if necessary heating until condensation is complete and isolating the product. In the arylhydrazine-N-sulphonate the aryl group may be phenyl or a - or b -naphthyl or a suitable substituted derivative thereof. The N-sulphonates are prepared by alkali metal sulphite reduction of aryldiazonium salts and the crude liquors thus obtained may be used, although the solid recrystallized N-sulphonates are preferred. Preferably two molar equivalents of acid are added to the N-sulphonate solution, the mixture refluxed for 1-2 hours, the excess acid over one molar equivalent neutralized with caustic alkali to about pH3 and the reactant added. When the free arylhydrazine is required for condensation the acid liquor is neutralized to about pH 8. In examples, (1) sodium phenyl- or p-tolyl-hydrazine-N-sulphonate is reacted with urea to give phenylor p-semicarbazide and phenylsemicarbazide is also obtained by using sodium isocyanate instead of urea; (2) the reaction liquor from the sodium sulphide reduction of benzene- or p-toluene-diazonium chloride gives similar results to (1).