Carbocation

A carbocation is an organic ion with a positively charged carbon atom. Its electron deficiency makes it a reactive intermediate in many organic reactions.

SN1 reaction: A nucleophilic substitution reaction whose rate-determining step is formation of a carbocation. Its slow ionization step creates the carbocation intermediate.
Formal charge: A bookkeeping charge assigned to an atom by comparing its valence electrons with its bonding and nonbonding electrons. It identifies the positive charge assigned to the carbocation carbon.
Carbanion: An organic ion in which a carbon atom bears a negative charge. It has the opposite charge and electron-rich character of a carbocation.
Friedel–Crafts alkylation: An electrophilic aromatic substitution that attaches an alkyl group to an aromatic ring using a Lewis acid catalyst. Its electrophile can be a carbocation formed from an alkyl halide.
E1 reaction: An elimination reaction in which a leaving group departs before a base removes a proton. The departing group forms a carbocation before the alkene appears.
Valence-shell electron-pair repulsion theory: A model that predicts molecular shape from repulsions among electron domains around an atom. The three-coordinate carbocation center is typically approximately planar.
Free radical: A chemical species containing an atom or group with an unpaired electron. A radical has an unpaired electron rather than a formally positive carbon.
Pinacol rearrangement: An acid-catalyzed rearrangement that converts a vicinal diol into a carbonyl compound. Loss of water creates a carbocation that undergoes a group shift.
Carbocation rearrangement: A shift of a hydrogen or carbon group that changes a carbocation's carbon framework. A shift can replace an initially formed carbocation with a more stable one.
Orbital hybridization: A model that combines atomic orbitals to describe bonding orbitals in molecules. The positively charged carbon is commonly described as sp²-hybridized.

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