The Benzyl Group and Its Reactivity

FIGURE 13.70 The position adjacent to a benzene ring is quite analogous to the allylic position. 

FIGURE 13.71 The resonance stabilization of the benzylic cation makes its formation relatively easy. Accordingly, SnI reactions of benzylic compounds containing good leaving groups are quite fast. 

In the benzyl cation itself (Fig. 13.72), the positive charge is borne by 4 carbons, in the benzhydryl cation (Ph2C H) (the benzhydryl group is Ph2CH) by 7 carbons, and in the trityl cation (Ph3C ) by a whopping 10 carbons. 

A composite picture in which the positions sharing the positive charge are shown as (+) 

Benzhydryl chloride The benzhydryl cation—7 resonance forms 

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