Angeli—Rimini reaction

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. 

Because this impurity is not easily removed from the desired prodnct, the Angeli-Rimini reaction has been seldom nsed in organic synthesis. 

Angelo Angeli s name, along with that of Enrico Rimini (1874—1917), is often associated with the chemical reaction that bears their names. In 1896 Angeli, and independently Rimini, discovered the reaction between an aldehyde and a sulfonamide to form a hydroxamic acid they published their discoveries in the same year [115, 116]. The reaction was mainly used as a chemical test in the dairy industry for detecting the presence of aldehydes as a consequence of food storage. The Angeli-Rimini reaction has been recently applied in solid-phase synthesis [117]. 

Fig. 4.9 Step 1 of the Angeli-Rimini Reaction Formation of the acid amide intermediate...

The reaction is based on an early observation by Angeli and Ahrens that Piloty s acid converted aldehydes to hydroxamic acids, and this has formed the basis of the Angeli-Rimini aldehyde test. Di Maio and Tardella propose the above reaction sequence, consistent with the observed second-order kinetics. The possibility that benzenesulfon-hydroxamic acid would decompose in alkali to give nitroxyl (HNO)... 

Reaction with Benzenesulfohydroxamic Acid (According to Angeli-Rimini)... 

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