G+C ZG− Heterolysis C+ + Z−
Carbocation
G−C ZG+ Heterolysis C− + Z+
Carbanion
- Carbocations have six electrons in their valence shell, and are electron
deficient. ⇒ Carbocations are Lewis acids.
- Most carbocations are short-lived and highly reactive.
- Carbonium ion (R+) Ammonium ion (R 4 N+)
- Carbocations react rapidly with Lewis bases (molecules or ions that can donate
electron pair) to achieve a stable octet of electrons.
C+ + − C
Carbocation
B B
(a Lewis acid)
Anion
(a Lewis base )
C+ + C
Carbocation
O
(a Lewis acid)
Water
(a Lewis base)
H
O + H
H
H
- Electrophile: “electron-loving” reagent
- Electrophiles seek the extra electrons that will give them a stable valence shell of
electrons.
- A proton achieves the valence shell configuration of helium; carbocations
achieve the valence shell configuration of neon.
- Carbanions are Lewis bases.
- Carbanions donate their electron pair to a proton or some other positive center to
neutralize their negative charge.
