Preferred Label : neighbouring group participation;
IUPAC definition : The direct interaction of the reaction centre (usually, but not necessarily, an incipient
carbenium centre) with a lone pair of electrons of an atom or with the electrons of
a σ- or π-bond contained within the parent molecule but not conjugated with the reaction
centre. A distinction is sometimes made between n-, σ- and π-participation. A rate
increase due to neighbouring group participation is known as 'anchimeric assistance'.
'Synartetic acceleration' is the special case of anchimeric assistance ascribed to
participation by electrons binding a substituent to a carbon atom in a β-position
relative to the leaving group attached to the α-carbon atom. According to the underlying
model, these electrons then provide a three-centre bond (or 'bridge') 'fastening together'
(as the word 'synartetic' is intended to suggest) the α- and β-carbon atoms between
which the charge is divided in the intermediate bridged ion formed (and in the transition
state preceding its formation). The term synartetic acceleration is not widely used.;
Origin ID : N04100;
See also
The direct interaction of the reaction centre (usually, but not necessarily, an incipient
carbenium centre) with a lone pair of electrons of an atom or with the electrons of
a σ- or π-bond contained within the parent molecule but not conjugated with the reaction
centre. A distinction is sometimes made between n-, σ- and π-participation. A rate
increase due to neighbouring group participation is known as 'anchimeric assistance'.
'Synartetic acceleration' is the special case of anchimeric assistance ascribed to
participation by electrons binding a substituent to a carbon atom in a β-position
relative to the leaving group attached to the α-carbon atom. According to the underlying
model, these electrons then provide a three-centre bond (or 'bridge') 'fastening together'
(as the word 'synartetic' is intended to suggest) the α- and β-carbon atoms between
which the charge is divided in the intermediate bridged ion formed (and in the transition
state preceding its formation). The term synartetic acceleration is not widely used.