A carbon acid is a chemical acid that loses a proton from a carbon-hydrogen bond, producing a carbanion or a resonance-stabilized related species. The name refers to the atom bearing the acidic hydrogen, not to every compound containing carbon.
For example, deprotonation of acetone next to its carbonyl group gives an enolate. Delocalization of the negative charge makes this hydrogen much more acidic than an ordinary alkane hydrogen. Carbon acidity therefore explains how carbon nucleophiles arise in reactions such as the aldol reaction, while the actual acid strength depends strongly on substituents and solvent.
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