Question

The ease of dehydrohalogenation of alkyl halide with alcoholic $KOH$ is

• A. $3^{o} < 2^{o} < 1^{o}$
• B. $3^{o} > 2^{o} >1^{o}$
• C. $3^{o} < 2^{o} > 1^{o}$
• D. $3^{o} > 2^{o} < 1^{o}$

Answer 1

Answer: (B)

$3^{o} > 2^{o} >1^{o}$

Answer 2

According to Saytzeff rule, any alkyl halide that gives a more highly substituted (more stable) alkene undergoes dehydrohalogenation faster than the one which gives a less highly substituted (less stable) alkene. Thus, the ease of dehydrohalogenation of different alkyl halides having the same halogen decreases in the order
tertiary $\left(3^{\circ}\right)>$ secondary $\left(2^{\circ}\right)>$ primary $\left(1^{\circ}\right)$