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Carbocations as reactive intermediates usually are demonstrated in organic chemistry labs as unimolecular elimination (E1) reactions (1, 2) with the accompanying skeletal rearrangements (3) or in solvolytic kinetic experiments (4). As with many instructional experiments, these reactions are illustrative in nature with little student discovery required. Often, the experimental outcome can be predicted through similarities with examples given in the textbook or in lecture. In contrast, experiments that yield unpredictable products help students to develop analytical and problem-solving skills. The advantages of discovery-based laboratory exercises have been discussed elsewhere (5-7). One such experiment is described here.
The Ritter reaction involves the in situ trapping of a carbocation intermediate by a nitrile followed by hydrolysis in an aqueous workup to produce an amide (8-10).
Although amides are prepared more commonly by the reaction of amines with acid chlorides, the Ritter reaction is an easy method for the preparation of amides via stabilized carbocations. As one of the few synthetic routes to amides of N-tertiary alkyl amines (8), the subsequent hydrolysis of the amide to liberate an...