Leaving group

Atom(s) that detach from the substrate during a chemical reaction

In organic chemistry, a leaving group typically means a molecular fragment that departs with an electron pair during a reaction step with heterolytic bond cleavage. In this usage, a leaving group is a less formal but more commonly used synonym of the term nucleofuge; although IUPAC gives the term a broader definition. A species' ability to serve as a leaving group can affect whether a reaction proceeds at a meaningful rate, as well as what mechanism the reaction takes.

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