To put it another way, although we have seen many examples of carbon electrophiles, we have not seen a reaction with a carbon atom acting as a nucleophile or a leaving group. In order for a carbanion ...To put it another way, although we have seen many examples of carbon electrophiles, we have not seen a reaction with a carbon atom acting as a nucleophile or a leaving group. In order for a carbanion to be a reasonable participant in an aqueous reaction - a nucleophile or leaving group - there clearly must be some kind of powerful stabilizing factor involved which acts to delocalize the unbonded electron pair, and its associated negative charge, away from the carbon atom.