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Write structures of various carbocatins that can be obtained from 2-methylbutane. Arrange these carbocation in order of increasing stability |
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Answer» Solution :2-methyl butane has four different sets of equivalent H atoms marked as 1, 2, 3 and 4. `overset(1)(C )H_(3)- underset(underset(CH_(3))(|))overset(2)(C )H- overset(3)(C )H_(2) - overset(4)(C )H_(3)` Removal of ONE hydrogen from any of these equivalent sets of hydrogen gives four different CARBONCATIONS (a), (b), (c ), (d) as shown below: (a) Minimum STABLE  (b) Medium stable (-ve `CH_(3)` has strong +1 effect)  (c ) Maximum stable +I effect of `CH_(3)CH_(2)` is medium  (d) Stability of (d) `gt` Stability of (a)  Now stability of carbocations decreases in the order: `3^(@) gt 2^(@) gt 1^(@)` `therefore` (b) `gt` (c ) `gt` [(a) and (d)] but stability of (d) is more than (a) because +I containing alkyl group `(CH_(3))_(2)CH CH_(2)`- is more strong is (d)  `therefore` Decreasing order of stability : `(b) gt (c ) gt (d) gt (a)` and lecresing order of stability : `(a) lt (b) lt (c ) lt (b) rarr` stability increase `rarr` In ADDITION based on no of hyperconjugation `alpha` stability so same stability order is obtained |
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