Bond dissociation enthalpy of `C_(6)H_(5)CH_(2)` - H bond is much less than `CH_(3)` - H bond. Explain.

Explanation

Benzyl radical `(C_(6)H_(5)overset(*)(C)H_(2))` produced by homolytic cleavage of `C_(sp^(3))-H` bond of toluene is considerably stabilised by resonance. But, the stability of methyl radical `(overset(*)(C)H_(3))` obtained by homolytic fission of the C - H bond of methane is not stabilised by any factor and in face, it is very much unstable. Thus, the C - H bond dissociation enthalpy of toluene is much less than the C - H bond dissociation enthaply of methane.