Carbanion

In organic chemistry, a carbanion is an anion in which carbon is negatively charged.^{[1][failed verification]}

Formally, a carbanion is the conjugate base of a carbon acid:

R₃CH + B⁻ → R₃C⁻ + HB

where B stands for the base. The carbanions formed from deprotonation of alkanes (at an sp³ carbon), alkenes (at an sp² carbon), arenes (at an sp² carbon), and alkynes (at an sp carbon) are known as alkyl, alkenyl (vinyl), aryl, and alkynyl (acetylide) anions, respectively.

Carbanions have a concentration of electron density at the negatively charged carbon, which, in most cases, reacts efficiently with a variety of electrophiles of varying strengths, including carbonyl groups, imines/iminium salts, halogenating reagents (e.g., N-bromosuccinimide and diiodine), and proton donors. A carbanion is one of several reactive intermediates in organic chemistry. In organic synthesis, organolithium reagents and Grignard reagents are commonly treated and referred to as "carbanions." This is a convenient approximation, although these species are generally clusters or complexes containing highly polar, but still covalent bonds metal–carbon bonds (M^δ+–C^δ−) rather than true carbanions.