NGP By An Aromatic Ring
In the case of a benzyl halide the reactivity is higher for the because the SN2 transition state enjoys a similar overlap effect to that in the allyl system.
An aromatic ring can assist in the formation of a carbocationic intermediate called a phenonium ion by delocalising the positive charge.
When the following tosylate reacts with acetic acid in solvolysis then rather than a simple SN2 reaction forming B, a 48:48:4 mixture of A, B and (C+D) was obtained .
The mechanism which forms A and B is shown below.
Read more about this topic: Neighbouring Group Participation
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