Solvent effect in dissociation of substituted benzenesulphonamides in dimethylformamide, dimethyl sulphoxide, and acetonitrile

Abstract

Dissociation constants of fifteen substituted arenesulphonamides of general formula XC 6 H 4 • . S02NH2 (or X2C6H3S02NH2) have been measured by potentiometric titration in dimethylformamide, dimethyl sulphoxide, and acetonitrile. The Hammett substitution correlations have been calculated and interpreted for these media. The pK HA values measured and the results published earlier for methanol, ethanol, and water have been treated by multiple linear regression using the published set of the parameters characterizing solvents and by factor analysis using the short cycle and the target testing method.• Purification of solvents: Dimethyl sulphoxide and acetonitrile were purified according to Kolthoff 17 .18. Dimethylformamide was repeatedly distilled in vacuum in the presence of fused powdered potassium hydroxide. Traces of alkalis were removed by two subsequent vacuum distillations, and the solvent was dried by keeping over activated molecular sieve for 14 days.Preparation of tetrabutylammonium nitrophenoxides: Picric acid, 2,4-dinitrophenol, and 2,6-dinitrophenol were dissolved in methanol. The solutions were neutralized with 0·1 moll-1 tetra-

Structure-Reactivity-Spectra Correlations for Substituted Benzenesulfonamides

“…IV) the absolute values of the slopes a of the correlations for dissociation constants (pK A ) measured in three selected solvents follow the same order as found previously on the basis of the Hammett equation and factor analyses [11], i.e. :…”

“…This is in accordance with a previous observation [13] that for several organic compounds containing SO 2 groups only the wavenumbers of the n as ðSO 2 Þ but not for the, n s ðSO 2 Þ vibration correlate satisfactorily with the s substituent constants. All previously reported pK A values, determined in H 2 O, CH 3 OH and CH 3 CN [10,11], exhibit good or satisfactory correlations with PM3 theoretical data of the À ÀSO 2 NH 2 group; Eqs. (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27).…”

“…From the infrared spectral data of the investigated compounds only the wavenumbers of the asymmetric SO 2 vibration, n as ðSO 2 Þ and the arithmetic mean of the symmetric and asymmetric NH 2 stretching vibrations, nðNH 2 Þ were found to correlate with the dissociation constants, the Hammett substituent constants, the PM3 S¼ ¼O bond orders and the oxygen atom charge densities; Eqs. (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). This is in accordance with a previous observation [13] that for several organic compounds containing SO 2 groups only the wavenumbers of the n as ðSO 2 Þ but not for the, n s ðSO 2 Þ vibration correlate satisfactorily with the s substituent constants.…”

“…However, there is no systematic investigation of substituent effects on these chemical shifts. The most systematic approach to the study of substituent effects on both IR and NMR spectral data of substituted benzenesulfonamides can be found in the paper of De Benedetti et al [1] Recently, dissociation constants of substituted benzenesulfonamides in various solvents have been measured and treated by the Hammett equation [10][11][12]. The dissociation constants determined in three selected solvents were taken as a measure of the acidity of the benzenesulfonamide system and used in our further investigation.…”

“…Spectral Data (in ppm) for the Substituted Benzenesulfonamides(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) in Acetone-d 6 .…”