Ylide

An ylide or ylid (d or d) 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. Ylides are thus 1,2-dipolar compounds. They appear in organic ch...
Found on http://en.wikipedia.org/wiki/Ylide

ylide

(from the article `Wittig, Georg`) In investigating reactions involving carbanions, negatively charged organic species, Wittig discovered a class of organic phosphorus compounds called ...
Found on http://www.britannica.com/eb/a-z/y/9

Ylide

A chemical species produced (actually or notationally) by loss of a hydron from an atom directly attached to the central atom of an 'onium ion, e.g.
Found on http://www.chem.qmul.ac.uk/iupac/gtpoc/TtZ.html
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