Which will undergo fastest `S_(N)2` substitution reaction when treated with NaOH?

Options

A. `H_5C_2 - underset(H)underset(|)overset(CH_3)overset(|)C - Br`
B. `CH_3 - underset(CH_3) underset(|)overset(CH_3)overset(|)C - Br`
C. `H - underset(C_2H_5)underset(|)overset(CH_3)overset(|)C - Br`
D. `H - underset(Br)underset(|)overset(H)overset(|)C - CH_2 - CH_2 - CH_3`

Answer

D

Explanation

Primary alkyl halides undergo bimolecular núcleophilic substitution most readily.