Preferred Label : partial rate factor;
IUPAC definition : The rate of substitution at one specific site in an aromatic compound relative to
the rate of substitution at one position in benzene. For example, the partial rate
factor fpZ for i para /i -substitution in a monosubstituted benzene C sub 6 /sub
H sub 5 /sub Z is related to the rate constants k(C6H5Z) and k(C6H6) for the total
reaction (i.e. at all positions) of C sub 6 /sub H sub 5 /sub Z and benzene, respectively,
and % i para /i (the percentage i para /i -substitution in the total product formed
from C sub 6 /sub H sub 5 /sub Z) by the relation: \[f_{p} {{Z}} \frac{6\ k\left({C}_{6}{H}_{5}{Z}\right)}{k\left({C}_{6}{H}_{6}\right)}\
\frac{\%\ {para}}{100}\] Similarly for i meta /i -substitution: \[f_{m} {{Z}} \frac{6\
k\left({C}_{6}{H}_{5}{Z}\right)}{2\ k\left({C}_{6}{H}_{6}\right)}\ \frac{\%\ {meta}}{100}\]
(The symbols p f Z, m f Z, o f Z are also in use.) The term applies equally to the
i ipso /i position, and it can be extended to other substituted substrates undergoing
parallel reactions at different sites with the same reagent according to the same
rate law.;
Origin ID : P04421;
See also
The rate of substitution at one specific site in an aromatic compound relative to
the rate of substitution at one position in benzene. For example, the partial rate
factor fpZ for i para /i -substitution in a monosubstituted benzene C sub 6 /sub
H sub 5 /sub Z is related to the rate constants k(C6H5Z) and k(C6H6) for the total
reaction (i.e. at all positions) of C sub 6 /sub H sub 5 /sub Z and benzene, respectively,
and % i para /i (the percentage i para /i -substitution in the total product formed
from C sub 6 /sub H sub 5 /sub Z) by the relation: \[f_{p} {{Z}} \frac{6\ k\left({C}_{6}{H}_{5}{Z}\right)}{k\left({C}_{6}{H}_{6}\right)}\
\frac{\%\ {para}}{100}\] Similarly for i meta /i -substitution: \[f_{m} {{Z}} \frac{6\
k\left({C}_{6}{H}_{5}{Z}\right)}{2\ k\left({C}_{6}{H}_{6}\right)}\ \frac{\%\ {meta}}{100}\]
(The symbols p f Z, m f Z, o f Z are also in use.) The term applies equally to the
i ipso /i position, and it can be extended to other substituted substrates undergoing
parallel reactions at different sites with the same reagent according to the same
rate law.
