A carbanion is a negatively charged ion that contains a carbon atom with an extra pair of electrons. This extra electron pair gives the carbon a negative charge, making it a reactive species in organic chemistry. Carbanions can form during various chemical reactions, such as deprotonation, where a hydrogen atom is removed from a molecule. Carbanions play a crucial role in many organic reactions, including nucleophilic substitutions and additions. They can act as nucleophiles, meaning they can donate their extra electrons to positively charged species, such as alkyl halides or carbonyl compounds. Understanding carbanions is essential for studying organic synthesis and reaction mechanisms.