List the following compounds in order of increasing reactivity in an SN2 reaction. A. 2-Bromo-2-methylbutane, 1-Bromopentane, 2-Bromopentane
B. 1-Bromo-3-methylbutane, 2-Bromo-2-methylbutane, 2-Bromo-3-methylbutane
C. 1-Bromobutane, 1-Bromo-2,2-dimethylpropane, 1-Bromo-2-methylbutane, 1-Bromo-3-methylbutane

A- 1-Bromopentane

>2-Bromopentane> 2-Bromo-2-methylbutane

B- 1-Bromo-3-methylbutane>2-Bromo-3-methylbutane> 2-Bromo-2-methylbutane

C- 1-Bromobutane > 1-Bromo-3-methylbutane>1-Bromo-2-methylbutane>1-Bromo-2,2-dimethylpropane

Explanation:

We must bear in mind that the ease of SN2 reaction is methyl > primary> secondary> tertiary.

As a result of this all primary alky halides react faster towards SN2 than secondary and tertiary alkyl halides.

Also, compounds that may form more stable carbocations by 1,2- alkyl shifts are less likely to participate in SN2 reaction