Preferred Label : pseudo-catalysis;
IUPAC definition : If an acid or base is present in nearly constant concentration throughout a reaction
in solution (owing to buffering or the use of a large excess), it may be found to
increase the rate of that reaction and also to be consumed during the process. The
acid or base is then not a catalyst and the phenomenon cannot be called catalysis
according to the well-established meaning of these terms in chemical kinetics, although
the mechanism of such a process is often intimately related to that of a catalysed
reaction. It is recommended that the term pseudo-catalysis be used in these and analogous
cases (not necessarily involving acids or bases). For example, if a Brønsted acid
accelerates the hydrolysis of an ester to a carboxylic acid and an alcohol, this is
properly called acid catalysis, whereas the acceleration, by the same acid, of hydrolysis
of an amide should be described as pseudo-catalysis by the acid: the 'acid pseudo-catalyst'
is consumed during the reaction through formation of an ammonium ion. The terms 'general
acid pseudo-catalysis' and 'general base pseudo-catalysis' may be used as the analogues
of general acid catalysis and general base catalysis. The term 'base-promoted', 'base-accelerated'
or 'base-induced' is sometimes used for reactions that are pseudo-catalysed by bases.
However, the term 'promotion' also has a different meaning in other chemical contexts.;
Origin ID : P04924;
See also
If an acid or base is present in nearly constant concentration throughout a reaction
in solution (owing to buffering or the use of a large excess), it may be found to
increase the rate of that reaction and also to be consumed during the process. The
acid or base is then not a catalyst and the phenomenon cannot be called catalysis
according to the well-established meaning of these terms in chemical kinetics, although
the mechanism of such a process is often intimately related to that of a catalysed
reaction. It is recommended that the term pseudo-catalysis be used in these and analogous
cases (not necessarily involving acids or bases). For example, if a Brønsted acid
accelerates the hydrolysis of an ester to a carboxylic acid and an alcohol, this is
properly called acid catalysis, whereas the acceleration, by the same acid, of hydrolysis
of an amide should be described as pseudo-catalysis by the acid: the 'acid pseudo-catalyst'
is consumed during the reaction through formation of an ammonium ion. The terms 'general
acid pseudo-catalysis' and 'general base pseudo-catalysis' may be used as the analogues
of general acid catalysis and general base catalysis. The term 'base-promoted', 'base-accelerated'
or 'base-induced' is sometimes used for reactions that are pseudo-catalysed by bases.
However, the term 'promotion' also has a different meaning in other chemical contexts.
