| 摘要 |
A valuable starting material for the manufacture of tetrachlorothioindigo pigments is 2,5-dichlorophenylthioglycollic acid which is prepared by: (a) diazotizing 2,5-dichloroaniline with aqueous alkali metal nitrite at acidic pH to produce 2,5-dichlorophenyl-diazonium salt, (b) reacting the 2,5-dichlorophenyl-diazonium salt from (a) with thiourea in an aqueous medium at acidic pH in the presence of a catalyst to produce 2,5-dichlorophenyl-isothiuronium salt of the formula <IMAGE> wherein X(-) is an anion of a mineral acid, (c) hydroloyzing the 2,5-dichlorophenylisothiuronium salt from (b), without intermediate isolation, at alkaline pH to produce 2,5-dichlorothiophenol and (d) condensing the 2,5-dichlorothiophenol with monochloroacetic acid to produce 2,5-dichlorophenylthioglycollic acid.
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