Question

Which of the following compound has the highest $\stackrel{\ast }{C}-H$ bond energy?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

The free radicals formed from the given compounds are

The most stable free radical is (a) since it is a tertiary free radical.
The stability of the free radicals follows the order,
(a) > (b) > (c) > (d)
The compound which gives more stable radical have the higher ability to form such radical. Since, the radical formed by the homolytic fission of $C^{\ast }-H$, the compound which form stable radical will break the bond easily. The bond which can be easily breaks have the lesser bond energy.

$\text{Bond energy}\propto \frac{1}{\text{Stability of free radicals}}$

Thus, (d) forms least stable radical so it will have the highest $C^{\ast }-H$ bond energy.