Preferred Label : common-ion effect (on rates);
IUPAC definition : A reduction in the rate of certain reactions of a substrate RX in solution [by a path
that involves a pre-equilibrium with formation of R sup class plus /sup (or R sup
class minus /sup ) ions as reaction intermediates] caused by the addition to the
reaction mixture of an electrolyte solute containing the 'common ion' X sup class
minus /sup (or X sup class plus /sup ). For example, the rate of solvolysis of
diphenylmethyl chloride in acetone-water is reduced by the addition of salts of the
common ion Cl sup - /sup which causes a decrease in the quasi-equilibrium concentration
of the diphenylmethyl cation in the scheme: This phenomenon is a direct consequence
of the mass-law effect on ionization equilibria in electrolytic solution. More generally,
the common-ion effect is the influence of the 'common ion' on the reactivity due to
the shift of the dissociation equilibrium. It may also lead to an enhancement of the
rate.;
Origin ID : C01191;
See also
A reduction in the rate of certain reactions of a substrate RX in solution [by a path
that involves a pre-equilibrium with formation of R sup class plus /sup (or R sup
class minus /sup ) ions as reaction intermediates] caused by the addition to the
reaction mixture of an electrolyte solute containing the 'common ion' X sup class
minus /sup (or X sup class plus /sup ). For example, the rate of solvolysis of
diphenylmethyl chloride in acetone-water is reduced by the addition of salts of the
common ion Cl sup - /sup which causes a decrease in the quasi-equilibrium concentration
of the diphenylmethyl cation in the scheme: This phenomenon is a direct consequence
of the mass-law effect on ionization equilibria in electrolytic solution. More generally,
the common-ion effect is the influence of the 'common ion' on the reactivity due to
the shift of the dissociation equilibrium. It may also lead to an enhancement of the
rate.
