Benzene sulphohydroxamic acid

Benzenesulphohydroxamic Acid.1—Hydroxylamine hydrochloride (10 g.) is boiled under reflux condenser with just enough methyl alcohol to dissolve it, and when still hot is decomposed by a solution of 3 g. of sodium in 60 c.c. of ethyl alcohol, which should not be added too quickly. After the mixture has been cooled, precipitated sodium chloride is removed at the pump and 8-5 g. of benzenesulphonyl chloride are then added in small portions to the solution of free hydroxylamine. Most of the alcohol is now removed by distillation from the water bath, the hydroxylamine hydrochloride which has separated is removed by filtration, and the filtrate is evaporated to dryness in vacuo at a moderate temperature. The residue is extracted three times with 15 c.c. portions of boiling absolute ether. Evaporation of the combined ethereal extracts in an open dish yields the benzene sulphohydroxamic acid in the form of a mass of crystalline plates which are digested with cold chloroform and filtered with suction. Yield 5-6 g. Melting point 126°. 

The decomposition by alkalis of benzene sulphohydroxamic acid— from benzene sulphochloride and hydroxylamine—likewise leads, as was already mentioned, to the sulphinic acid (Piloty). 

Experiment 5. Angeli-Rimini Reaction.—A few drops of an aldehyde (any of those prepared) are dissolved in aldehyde-free 1 alcohol and about the same amount of benzene sulphohydroxamic acid (for the preparation of which see p. 192) is added in the case of aliphatic substances, twice as much of the acid is used. To this mixture, kept cool and shaken, 2 A-sodium hydroxide is added, in an amount judged to be about two molecular proportions. After standing for fifteen minutes the alkaline mixture is made just acid to Congo red and finally a drop of ferric chloride solution is added. An intense red colour is produced. 

It was mentioned on p. 193 that benzene sulphohydroxamic acid is decomposed by alkali into benzene sulphinic acid and the very unstable compound nitroxyl, 0=NH. If nitroxyl is produced in the presence... 

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