Question

Questions: Why is a benzylic C-H bond unusually weak?

Short answer

Answer

Benzylic C-H bond is unusually weak because the cleavage of the C-H bond gives a 1^o radical, which is stabilized by resonance.

Step-by-step solution

Stability

The presence of an unpaired electron forms a radical. It is represented by a dot.It is unstable and highly reactive. Its stability is governed by the degree of radical formed.

Explanation by resonance

Representation of resonance structures

Due to the resonance stabilization of benzylic radical, the C-H bond cleavage is easy.