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Arrange the following compounds in order of incraesing S_(N)2 reacitivity and explain: (i) 2-bromo-2-methylbutane, 1-bromopentane, 2-bromopentane. |
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Answer» Solution :`underset(2-"brome"-2-"methylbutane"(3^@))(CH_(3)-underset(Br)underset(|)overset(CH_3)overset(|)(C)-CH_(2)CH_(3))``underset(1-"bromopentane"(1^@))(CH_(3)CH_(2)CH_(2)CH_(2)CH_(2)Br)` `underset(1-"bromopentane"(1^@))(CH_(3)underset(Br)underset(|)CH-CH_(2)CH_(2)CH_(3))` The `S_(N)2` reacitivity of ALKYL halides depends on the steric hindrance at the reactingcentre. The tendency of nucleophilic attack increases with decrease in steric crowding. The steric hindrance in `S_(N)2` transition state PROGRESSIVELY increases from primary `(1^@)` halide to TERTIARY `(3^@)` halide. Thus, the `S_(N)2` reactivity of to tertiary `(3^@)` halide. Thus, the `S_(N)2` reactivity of these compounds follows the order: 1-bromopentane > 2-bromopentane > 2-bromo-2-methylbutane. |
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