248 PRACTICAL ORGANIC CHEMISTRY fore be used to obtain crystalline derivatives of hydroxyl compounds, and also of primary and secondary amines: tertiary amines cannot undergo sulphonylation. There is, however, one important difference between the benzoyl and the sulphonyl derivatives of amines. It has been shown that primary and secondary amines, when treated with benzoyl chloride, give mono- and di-substituted derivatives of benzamide, and when treated with benzenesulphonyl chloride, give similar derivatives of benzene sulphonamide. A carboxylic acid amide, such as benzamide, possesses only very weak amphoteric properties (p. 120), and is therefore practically neutral, and its derivatives are consequently insoluble in dilute aqueous solutions of alkalis or acids. A sulphonic acid amide, such as benzenesulphonamide, is devoid of basic properties, but has its acidic properties correspondingly increased, and therefore each of the hydrogen atoms in the-NH 1 group can in turn show marked acidic properties. It follows that
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