Rearrange the compounds of each of the following sets in order of reactivity towards S2 displacement:
i) 2-bromo-2-methylbutane, 1-bromopentane, 2-bromopentane
ii) 1-bromo-3-methylbutane, 2-bromo-2-methylbutane, 2-bromo-3-methylbutane
iii) 1-bromobutane, 1-bromo-2,2-dimethylpropane, 1-bromo-2-methylbutane
i) 2-bromo-2-methylbutane, 1-bromopentane, 2-bromopentane
ii) 1-bromo-3-methylbutane, 2-bromo-2-methylbutane, 2-bromo-3-methylbutane
iii) 1-bromobutane, 1-bromo-2,2-dimethylpropane, 1-bromo-2-methylbutane
Solution
S2 reactivity falls with crowding at and next to the α-carbon (1° > 2° > 3°; β-branching also hinders).
(i)
(ii)
(iii) all primary — β-branching decides:
(i)
(ii)
(iii) all primary — β-branching decides:
CBSE Class 12 Board · 2011 · All India · Subjective