7.50 draw all constitutional isomers with the molecular formula c4h9br, and then arrange them in order of: (a) increasing reactivity toward an sn2 reaction. (b) increasing reactivity toward an e2 reaction

Isomers are:

2-bromobutane (I)

2-bromo-2-methylpropane (II)

1-bromo-2-methylpropane (III)

1-bromobutane (IV)

for SN2 reaction :

IV > III > I > II

for E2 reaction is:

IV < III < I < II

Explanation:

The constitutional isomers are (structures are shown if figure):

2-bromobutane (I)

2-bromo-2-methylpropane (II)

1-bromo-2-methylpropane (III)

1-bromobutane (IV)

For SN2 reaction : the order of reactivity of alkyl halides is

tertiary < secondary < primary

For E2 reaction: the order of reactivity of alkyl halides is

tertiary > secondary > primary

Thus the order of reactivity for SN2 reaction is:

IV > III > I > II

The order of reactivity for E2 reaction is:

IV < III < I < II