Question
Which of the following is the correct order of decreasing $${S_N}2$$ reactivity?
A.
$${R_2}CHX > {R_3}CX > RC{H_2}X$$
B.
$$RCHX > {R_3}CX > {R_2}CHX$$
C.
$$RC{H_2}X > {R_2}CX > {R_3}CX$$
D.
$${R_3}CX > {R_2}CHX > RC{H_2}X$$
Answer :
$$RC{H_2}X > {R_2}CX > {R_3}CX$$
Solution :
In $${S_N}2$$ mechanism transition state is pentavelent. For
bulky alkyl group it will have sterical hinderance and smaller alkyl group will favour the $${S_N}2$$ mechanism. So the decreasing order of reactivity of alkyl halides is $$RC{H_2}X > {R_2}CX > {R_3}CX$$