Hammett sigma constants, special

TABLE 7.4 Special Hammett Sigma Constants ([Pg.785]

I) the hydrophobic term, 1-octanol/water partition coefficient, log KQyy, and two discrete variables, (2) the ability to accept hydrogen, Ha, and (3) the ability to donate hydrogen, Hd. Several electronic parameters were selected (4) the Hammett sigma constant for the para position (see Jaffe 1953), and its special cases, (5) (normalized), (6) (minus), and (7) (plus) (see Hansch and Leo 1979) (8) the polar or field parameter, F (Swain and Lupton 1968) and (9) the resonance parameters, R (Swain and Lupton 1968), (10) R°,... [Pg.335]

Considerable effort has been devoted to the determination of rate and equilibrium constants for benzene derivatives with meta- and pnrn-trifluoro-methyl substituents in a search for an exalted substituent effect which would provide evidence for special electron delocalization. Resonance interactions are generally detectable by such procedures. To illustrate, two sigma constants Op-NOi p-N(h with values of 0.78 and 1.24, respectively are necessary to describe the behavior of the nitro group quantitatively by the Hammett equation... [Pg.260]

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