Chapter 18: 18-28P (page 677)

Explain why \({{\rm{C}}_{\rm{6}}}{{\rm{H}}_{\rm{5}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{Br}}\)is not formed during the radical bromination of \({{\rm{C}}_{\rm{6}}}{{\rm{H}}_{\rm{5}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{C}}{{\rm{H}}_{\rm{3}}}\).

Short Answer

Expert verified

\({{\rm{C}}_{\rm{6}}}{{\rm{H}}_{\rm{5}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{Br}}\) is not formed during the radical bromination of \({{\rm{C}}_{\rm{6}}}{{\rm{H}}_{\rm{5}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{C}}{{\rm{H}}_{\rm{3}}}\) because benzylic radicals are more stable than primary radicals and they form the product.

Step by step solution

Halogenation of alkylbenzene

Benzylic halides are formed from alkyl benzene through radical halogenation reactions. Weaker benzylic C-H bonds are broken, and C-X (X is a halogen) is formed.

Stability of benzylic radical

During radical formation, there is a possibility of the formation of two radicals—benzylic and primary. Benzylic radicals are resonance stabilized; therefore, a benzylic bromide product is formed.

No other product is formed because the radical that gives the product (primary radical) is more unstable than the benzylic radical.