Preferred Label : Brønsted relation;
Detailed label : Brønsted relation;
IUPAC definition : The term applies to either of the equations: \[\frac{k_{{HA}}}{p} G\left ( \frac{q\
K_{{HA}}}{p} \right ) {\alpha}\] \[\frac{k_{{A}}}{q} G\left ( \frac{q\ K_{{HA}}}{p}
\right ) {-\beta} \] (or their logarithmic forms) where α, β and G are constants for
a given reaction series (α and β are called 'Brønsted exponents'), kHA and kA are
catalytic coefficients (or rate coefficients) of reactions whose rates depend on the
concentrations of HA and/or of A sup /sup . KHA is the acid dissociation constant
of the acid HA, p is the number of equivalent acidic protons in the acid HA, and q
is the number of equivalent basic sites in its conjugate base A sup class minus
/sup . The chosen values of p and q should always be specified. (The charge designations
of H and A are only illustrative.) The Brønsted relation is often termed the 'Brønsted
catalysis law' (or the 'Catalysis law'). Although justifiable on historical grounds,
this name is not recommended, since Brønsted relations are known to apply to many
uncatalysed and pseudo-catalysed reactions (such as simple proton (hydron) transfer
reactions). The term 'pseudo-Brønsted relation' is sometimes used for reactions which
involve nucleophilic catalysis instead of acid–base catalysis. Various types of Brønsted
parameters have been proposed such as βlg, βnuc, βeq for leaving group, nucleophile
and equilibrium constants, respectively.;
Origin ID : B00746;
See also
The term applies to either of the equations: \[\frac{k_{{HA}}}{p} G\left ( \frac{q\
K_{{HA}}}{p} \right ) {\alpha}\] \[\frac{k_{{A}}}{q} G\left ( \frac{q\ K_{{HA}}}{p}
\right ) {-\beta} \] (or their logarithmic forms) where α, β and G are constants for
a given reaction series (α and β are called 'Brønsted exponents'), kHA and kA are
catalytic coefficients (or rate coefficients) of reactions whose rates depend on the
concentrations of HA and/or of A sup /sup . KHA is the acid dissociation constant
of the acid HA, p is the number of equivalent acidic protons in the acid HA, and q
is the number of equivalent basic sites in its conjugate base A sup class minus
/sup . The chosen values of p and q should always be specified. (The charge designations
of H and A are only illustrative.) The Brønsted relation is often termed the 'Brønsted
catalysis law' (or the 'Catalysis law'). Although justifiable on historical grounds,
this name is not recommended, since Brønsted relations are known to apply to many
uncatalysed and pseudo-catalysed reactions (such as simple proton (hydron) transfer
reactions). The term 'pseudo-Brønsted relation' is sometimes used for reactions which
involve nucleophilic catalysis instead of acid–base catalysis. Various types of Brønsted
parameters have been proposed such as βlg, βnuc, βeq for leaving group, nucleophile
and equilibrium constants, respectively.