Carbocations:-
Carbocation is organic
molecules in several reactions particularly in nucleophilic substitution
reactions, that has a carbon atom bearing a positive charge and three bonds
instead of four that chemical intermediate sate carbon which has a positive
charge on it and carrying six electrons in its valence shell are called
carbocation.
Carbocation is classified in three types:
1.Primary(1o) Carbocation has one
carbon group attached to the carbon bearing the positive charge.
2.Secondary (2o) Carbocation has two
carbons attached to the carbon bearing the positive charge.
Stability of Carbocation:-
(3o)>(2o)>(1o )>Methyl
The Question raises here ...why is
Tertiary carbocation the most stable ?
Ans:- Because methyl groups are weakly electron
donating group by inductive effects and hyper-conjugation.
Less positive charge at
carbon then it will gain more stability where Methyl groups push electron
density towards the electron defficient carbocation center to stabilise the
positive charge. The more donating groups (like methyl group), the more the
positive charge will be stabilised.
Carbanions:-
The simplest carbanion, the methide ion (CH-3 ), is derived from the organic compound methane (CH4) by a loss of a proton (hydrogen ion, H+)
Stability of Carbanions:-
The stability of a
carbanion also depends on the nature of hybridized orbitals used by the
negatively charge carbon atom. A more electronegative carbon atom accomodates a
negative charge in a betterways and electronegativity of the C atom depends on
the nature of hybridization its uses. The primary carbanions more stable than
secondary and tertiary carbanions.
More negative charge at carbon it will be less stable
so
Methide ion (CH-3 )>(10 )>(20)> (3o)
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