Question

In S$_N$2 reactions, the correct order of reactivity for the following compounds $CH_3Cl,CH_3CH_2Cl, (CH_3 )_2CHCl$ and (CH$_3 )_3CCl$ is

• A. $CH_3Cl > (CH_3)_2CHCl > CH_3CH_2Cl > (CH_3)_3CCl$
• B. $CH_3Cl > CH_3CH_2 Cl > (CH_3)_2 CHCl >(CH_3)_3CCl$
• C. $CH_3CH_2Cl > CH_3Cl > (CH_3)_2CHCl > (CH_3)_3CCl$
• D. $(CH_3)_2CHCl > CH_3CH_2Cl > CH_3Cl > (CH_3)_3CCl$

Answer 1

Answer: (B)

$CH_3Cl > CH_3CH_2 Cl > (CH_3)_2 CHCl >(CH_3)_3CCl$

Answer 2

Rate of $S _{ N } 2$ reaction depends on steric crowding of alkyl halide. So order is

$CH _{3} Cl >\left( CH _{3}\right) CH _{2}- Cl >\left( CH _{3}\right)_{2} CH - Cl >\left( CH _{3}\right)_{3} CCl$