Question

Rank the bond dissociation energies of the bonds indicated with the arrows. (from smallest to largest).

• A. $1<2<3$
• B. $3<2<1$
• C. $2<3<1$
• D. $3<1<2$

Answer 1

The correct option is D $3<1<2$

The dissociation of $C-H$ bond will result into a carbon radical. Primary carbon radical is the least stable whereas tertiary one is the most stable as tertiary carbon radical has stabilizing $+I$ effect of $2-methyl$ groups.

Hence, dissociation of a primary carbon-hydrogen bond will be difficult, requiring the most energy. In case of tertiary carbon, this energy required will be least.

Therefore, order of bond dissociation energy is- $3<1<2$ i.e., $tertiary<secondary<primary$.