A multiparameter extension of the Hammett equation to quantify the role of enhanced resonance effects on the reactivity of meta- and para-substituted benzene derivatives, e.g.
lg k = lg ko + + r (+ - )]The parameter r gives the enhanced resonance effect on the scale (+-), or (--), respectively.
See also -value, -constant. See YUKAWA and TSUNO (1959); SHORTER (1973).
Z-valueSee below under Z-value.
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