Leaving group facts for kids

In chemistry, a leaving group is an atom or molecule that leaves another molecule during a reaction. This reaction can be for example a nucleophilic substitution. In this case the leaving group gets a pair of electrons. Some leaving groups are better than others. This is because some atoms or molecules like getting extra electrons. The halides are a good example of good leaving groups.

In this S_N2 reaction, bromide (Br⁻) is the leaving group and hydroxide (OH⁻) is the nucleophile.

The type of leaving group can change the type of reaction that happens. For example, bad leaving groups make an SN1 reaction more difficult, while they make an SN2 reaction easier.

Images for kids

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  Common mechanistic contexts that involve the departure of a nucleofugal leaving group. The leaving group (LG) is shown in red. Top: SN2 reaction; middle/left: first step of SN1 and E1 reactions; middle/right: second step of E1cb, AAC2, and BAC2 reactions; bottom: E2 reaction.

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  In an ionization reaction, as in all reactions that involve leaving group departure, the leaving group bears a larger negative charge in the transition state and products than it does in the starting materials

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  The ability of hyper leaving groups is enhanced by entropic factors

See also

In Spanish: Grupo saliente para niños