Preferred Label : dual substituent-parameter equation;
IUPAC definition : In a general sense, any equation which expresses substituent effects in terms of two
parameters. However, in practice the term is used more specifically for an equation
for summarizing the effects of i meta /i - or i para /i - substituents (i m or
p) strong X /strong on chemical reactivity, spectroscopic properties, etc. of a
probe site strong Y /strong in benzene or other aromatic system. \[P {rm{i}} \rho
_{I} {rm{i}}\ σ _{I} \rho _{R} {rm{i}}\ σ _{R}\] P is the magnitude of the property
strong Y /strong for substituent strong X /strong , expressed relative to the property
for X H; σ I and σ R are inductive or polar and resonance substituent constants,
respectively, there being various scales for σ R and ρ R are the corresponding regression
coefficients.;
Origin ID : D01866;
See also
In a general sense, any equation which expresses substituent effects in terms of two
parameters. However, in practice the term is used more specifically for an equation
for summarizing the effects of i meta /i - or i para /i - substituents (i m or
p) strong X /strong on chemical reactivity, spectroscopic properties, etc. of a
probe site strong Y /strong in benzene or other aromatic system. \[P {rm{i}} \rho
_{I} {rm{i}}\ σ _{I} \rho _{R} {rm{i}}\ σ _{R}\] P is the magnitude of the property
strong Y /strong for substituent strong X /strong , expressed relative to the property
for X H; σ I and σ R are inductive or polar and resonance substituent constants,
respectively, there being various scales for σ R and ρ R are the corresponding regression
coefficients.
