Effect of para Substitution on Dissociation of N-Phenylbenzenesulfonamides

Abstract

The reaction of substituted anilines and benzenesulfonyl chlorides has been used to prepare 49 substituted N-phenylbenzenesulfonamides of general formula 4-X-C 6 H 4 SO 2 NHC 6 H 4 -Y-4′. Their purity was checked by elemental analysis. The substituents X and Y include H, CH 3 , CH 3 O, Cl, Br, CN, and NO 2 . The dissociation constants of all compounds were determined by potentiometric titration in methanol, acetonitrile, N,N-dimethylformamide, and pyridine. The obtained dissociation constants, pK HA , were correlated with various sets of substituent constants. It was found that the effects of substituents X and Y on the dissociation are best described by using the Hammett equation with σ p constants and the Yukawa-Tsuno equation with σ p -and σ p constants, respectively. This result confirms the direct conjugation of Y substituent with the reaction centre. The explained variability using the additive model was above 96% in all the solvents used. The data also provided information about the transmission effect of the SO 2 group. The average dissociation constants were further processed by the latent variables methods, principal components and conjugated deviations analyses.

Primary and Secondary Amines by Flavin‐Photocatalyzed Consecutive Desulfonylation and Dealkylation of Sulfonamides

“…However, we failed to cleave the N−S bond in either 4 e or 5 e , as representatives of secondary perfluoroalkanesulfonamides (entries 13 and 14). We surmise that this outcome is most likely due to the relatively acidic NH group in triflamides (p K a =5.7 for N ‐phenyltriflamide) [49] as compared to tosylamides (p K a =23.9 for N ‐phenyltosylamide), [50] resulting in the formation of an anion that is extremely difficult to reduce. The triflyl or nonaflyl group was also readily removed from the corresponding aryl triflates 6 and aryl nonaflates 7 by applying the general procedure (entries 15 and 16).…”

Absolute pKas of Sulfonamides in Ionic Liquids: Comparisons to Molecular Solvents

“…The knowledge of sulfonamide acidities is important to the pharmaceutical industry because it delivers valuable information on the mechanisms of drug actions and metabolisms. The acidities of sulfonamides have been investigated extensively in conventional molecular solvents . However, until now almost no attention has been paid to the acidities of N–H bonds in ILs.…”

Development of a Robust Protocol for the Determination of Weak Acids’ pKa Values in DMSO

“…Depending on the charge states of the acids and conjugate bases, the polarity of the solvent and the ability to act as hydrogen bond acceptor or donor can shift the pK a values for several orders of magnitude. For this reason pK a values of weak acids have been determined in various solvents, mostly in DMSO, 1 in acetonitrile, 11 in N,N-dimethylformamide (DMF), 12 and in cyclohexylamine. 13 An excellent overview on this work has been given by Leito et al 14 The determination of weak acids' pK a values was dominated by the tremendous amount of work finished by Bordwell et al, who determined the acidity in DMSO of more than 1000 compounds.…”