Question

Which of the following compounds undergoes dehydrochlorination most easily when treated with alcoholic $KOH$ ?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

Rate of dehydrohalogenation in $R-X$
with respect to $\alpha$-carbon:
$3^{\circ }>2^{\circ }>1^{\circ }$
This is because, alkene so formed from a $3^{\circ }$ alkyl halide is most stable due to maximum number of $\alpha$-hydrogens

In (a) $\alpha$-carbon is $1^{\circ }$
In (b) $\alpha$-carbon is $1^{\circ }$
In (c) $\alpha$-carbon is $2^{\circ }$
In (d) $\alpha$-carbon is $3^{\circ }$

So, compound (d) undergoes dehydrochlorination most easily forming the most stable alkene when treated with alcoholic $KOH$