An Extended Table of Hammett Substitutent Constants Based on the Ionization of Substituted Benzoic Acids

Kinetics of the Z-E isomerization of monosubstituted azobenzenes in polar organic and aqueous micellar solvents

“…By plotting the logarithm of kobs for the investigated 4-X-azobenzenes in methanol and ethanol against the corresponding  substituent constants 34 V-shaped Hammett plots are obtained ( Figure 6). The n-Butyl derivative has been excluded from the correlations due to the mentioned peculiar solute-solvents interactions in methanol/water mixtures.…”

Compilation and critical evaluation of structure-reactivity parameters and equations - Part I: Values of σm, and σp based on the ionization of substituted benzoic acids in water at 25 C (Technical Report)

“…The number of determinations is usually too small for any formal treatment of errors to be applicable. McDaniel and Brown (1958) attempted to deal with this problem in terms of a 'limit of uncertainty', which was not too clearly defined. Exner (1978) adopted the same practice.…”

“…the rates of alkaline hydrolysis of ethyl benzoates in 87.83% ethanol-water at 3OOC) by using the data relating to substituents for which d values based on the ionization of substituted benzoic acids were available, and then applying the established p values to the relevant experimental results for other substituents. Thus, right from the start, as pointed out by McDaniel and Brown (1958), there was but a limited number of 'primary' ts values; these were a larger number of 'secondary' ts values, and even some which might be termed 'tertiary', the last-mentioned being based on correlation equations which had been established by using a mixture of primary and secondary ts values. This situation, in fact, led McDaniel and Brown (1958) to suggest that secondary ts values should as far as possible be based on ionization constants of benzoic acids in aqueous organic solvents such as 50% ethanol-water, rather than on rate or equilibrium measurements for a wider range of systems.…”

Mass spectral studies of metal chelates. VI. Mass spectra and appearance potentials of β-diketonates of copper(II)

“…) that the presence of the copper and oxygen atoms will mean that the chelate ring will not be truly aromatic. The o+ constants of Brown and Okamoto (27) have been used although use of the o values of McDaniel and Brown (28) leads to the same conclusions. In one plot the values used have been selected with respect to the position of the substituent relative to the copper atom, i.e.…”