4,4-di:amino-stilbene-2,2-di:sulphonic acid - by redn. of corresp. di:nitro cpd. in aq. medium presence of hydrogenation catalyst with forming acid or salt as reducing agent

摘要

4,4'-Diaminostilbene-2,2'- disulphonic acid (I) is produced by redn. of 4,4'-dinitrostilbene- 2,2'-disulphonic acid (II) in aq. medium in the presence of hydrogenation catalysts, using formic acid or a salt thereof as reducing agent (III). (I) is claimed as such. Pref. catalyst is a metal of Sub-Gp. VIII, pref. a Pd catalyst with Na formate as reducing agent; redn. is carried out at 20-80 deg.C and normal pressure. USE/ADVANTAGE - (I) is useful as an intermediate for the prodn. of optical brighteners (claimed). The process does not require the use of hydrogen under pressure, and produces no effluent problems on the large scale (contrast prior-art processes).