Thiosemicarbazones special

Isothiazoles have also been incorporated into a wide range of established drugs including phenothiazines,123 sulfones,121 sulfonamides,3,66,156 thiosemicarbazones,140,157 amidines,158 nitrohetero-cycles,159 and benzimidazoles,160 but this approach does not appear to have resulted in any major improvements. However, many isothiazoles not directly related to known drugs have biological activity, and representatives are listed in Table I, No attempt has been made to include the numerous patents which mention isothiazole derivatives as part of a series, but for which no special claims are made. 

Thiosemicarbazones are of special interest, as they form insoluble compounds with monovalent metals such as silver, copper and mercury, which may be an aid to their separation from mixtures and to their quantitative determination. The colour of the nitrated phenylhydrazine derivatives can be characteristic of the type of carbonyl group. p-Nitrophenylhydrazones of aliphatic compounds are yellow or brown, those of aromatic compounds red. 2,4-Dinitrophenylhydrazones of saturated aliphatic aldehydes and ketones are yellow or orange, those of a, -unsaturated carbonyls are red, and those of simple aromatic compounds are yellow, orange or red. They are usually formed in excellent yields. 

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