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'Stability of carbocations depends upon ...

'Stability of carbocations depends upon the electron releasing inductive effect of groups adjacent to positively charged atom involvement of neighbouring groups in hyperconjugation and resonace''.
Write structure of various carbocations that can be obtained from 2-methylbutane. Arrange these carbocations in order of increasing stability

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Four possible carbocations can arise from 2-methylbutane. These are :
`{:(CH_(3)-CH-CH_(2)-CH_(3) overset(-H^(+))(rarr)CH_(3)-CH-CH_(2)-overset(o+)(C)H_(2)" "CH_(3)-CH-overset(o+)(C)H-CH_(3)" "CH_(3)-overset(o+)(C)-CH_(2)-CH_(3)" "overset(o+)(C)H_(2)-CH-CH_(2)-CH_(3)),(" |"" |"" |"" |"" |"),(" "CH_(3)" "CH_(3)" "CH_(3)" "CH_(3)" "CH_(3)),(" "Ioverset(@)((1))" "IIoverset(@)((2))" "IIIoverset(@)((3))" "IVoverset(@)((1))):}`
Order of increasing stabilities of the carbocations is : `(I) lt (IV) lt (II) lt (III)`
Explanation. We know that the order of relative stabilities of carbocations is : tertiary `gt` secondary `gt` primary. In this case, carbocations (III) and (II) are tertiary and secondary respectively. carbocations (I) and (IV) are both primary carbocations. Out of the two, structure (IV) is more stable because the electron releasing - `CH_(3)` group (-I effect) is present at `alpha`-position w.r. to the carbon atom carrying positive charge. In structure (I), it is present at the `beta`-position. the increasing order of stabilities of carbocations is : `(I) lt (IV) lt (II) lt (III)`.
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