An ylide (/ˈɪlaɪd/)[1] or ylid (/ˈɪlɪd/) is a neutral dipolar molecule containing a formally negatively charged atom (usually a carbanion) directly attached to a heteroatom with a formal positive charge (usually nitrogen, phosphorus or sulfur), and in which both atoms have full octets of electrons. The result can be viewed as a structure in which two adjacent atoms are connected by both a covalent and an ionic bond; normally written X+–Y−. Ylides are thus 1,2-dipolar compounds, and a subclass of zwitterions.[2] They appear in organic chemistry as reagents or reactive intermediates.[3]
The class name "ylide" for the compound should not be confused with the suffix "-ylide".