Question

The reactivity of hydrogen atom in an alkane towards substitution by bromine atom is

• A. > >
• B. < <
• C. > <
• D. < >

Answer 1

The correct option is B < <

Homolytic bond dissociation energy is inversely related to the stability of radicals.
$1^{\circ }H\Delta H=98Kcal/Mol$
$2^{\circ }H\Delta H=94Kcal/Mol$
$3^{\circ }H\Delta H=91Kcal/Mol$
Thus the order of reactivity is $1^{\circ }H$ < $2^{\circ }H$ < $3^{\circ }H$