Haloalkanes and Haloarenes - Result Question 46
####46. The correct order of increasing reactivity of $C-X$ bond towards nucleophile in the following compounds is:
[2010]
(I)
(II)
(III)
(IV)
(a) I $<$ II $<$ IV $<$ III
(b) II $<$ III $<$ I $<$ IV
(c) IV $<$ III $<$ I $<$ II
(d) III $<$ II $<$ I $<$ IV
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Solution:
- (a) Tertiary alkyl halide is most reactive towards nucleophilic substitution because the corresponding carbocation $(3^{\circ})$ is most stable. Aryl halide is least reactive due to partial double bond character of the $C-Cl$ bond.
Presence of - $NO_2$ groups in ortho and para positions increases the reactivity of the $-Cl$ towards nucleophiles.
$ \begin{gathered} (CH_3)_3-C-X>(CH_3)_2-CH-X> \\ \text{ III } \end{gathered} $
II I
or I $<$ II $<$ IV $<$ III
