Neighbouring group participation

In <a href="/facts/Organic_chemistry/djxhxaNg">organic chemistry</a>, neighbouring group participation (NGP, also known as anchimeric assistance) has been defined by the <a href="/facts/International_Union_of_Pure_and_Applied_Chemistry/2AV6myCK">International Union of Pure and Applied Chemistry</a> (IUPAC) as the interaction of a reaction centre with a <a href="/facts/Lone_pair/Q6kEAC4g">lone pair</a> of <a href="/facts/Electron/L0KBo5cW">electrons</a> in an atom or the electrons present in a <a href="/facts/Sigma_bond/CSyEe5CY">sigma</a> or <a href="/facts/Pi_bond/3Q6LAGYK">pi bond</a> contained within the parent molecule but not <a href="/facts/Conjugated_system/Ddx9qzox">conjugated</a> with the reaction centre. When NGP is in operation it is normal for the <a href="/facts/Reaction_rate/Prwvxq0y">reaction rate</a> to be increased. It is also possible for the <a href="/facts/Stereochemistry/XkcRVNwd">stereochemistry</a> of the reaction to be abnormal (or unexpected) when compared with a normal reaction. While it is possible for neighbouring groups to influence many reactions in organic chemistry (e.g. the reaction of a <a href="/facts/Diene/F5NxrLPW">diene</a> such as 1,3-cyclohexadiene with <a href="/facts/Maleic_anhydride/KfBTU8n4">maleic anhydride</a> normally gives the <a href="/facts/Endo_isomer/3fPeu0F6">endo isomer</a> because of a secondary effect {overlap of the carbonyl group π orbitals with the transition state in the <a href="/facts/Diels-Alder/zc6dVpKl">Diels-Alder</a> reaction}) this page is limited to neighbouring group effects seen with <a href="/facts/Carbocation/vIggUxTh">carbocations</a> and <a href="/facts/SN2_reaction/0N06Ra0R">SN2 reactions</a>.

Neighbouring group participation open-in-new

Neighbouring group participation