List of top Chemistry Questions on Haloalkanes and Haloarenes asked in UP Board XII

Write the mechanism of bimolecular nucleophilic substitution reaction ($S_N2$) of alkyl halide.

The increasing order of reactivity of the following compounds in $S_N1$ reaction is:
Compounds:
A. $(CH_3)_3CBr$
B. $CH_3CH_2CH_2CH_2Br$
C. $(CH_3)_2CHCH_2Br$
D. $CH_3CH(Br)CH_2CH_3$