Effect of solvent composition on the acidity of phenols in dimethyl sulfoxide-water mixtures

Abstract

The effect of solvent composition on the acidity of substituted phenols in DMSO-H 2 O systems was examined. It is shown that in DMSO-H 2 O mixtures with up to 35 mol% DMSO there is a linear relationship between the pK a values of monosubstituted phenols in the binary solvent mixtures of different compositions and the corresponding pK a values in water. This leads to an equation relating the slope and intercept terms, pK a (DMSO-H 2 O) = slope[pK a (H 2 O)] intercept. The basis of this relationship in the Kirkwood-Westheimer equation is examined. The significance of a possible 'supersolvent' is discussed. The applicability of the relationships derived herein to other rate-equilibria relationships and solvent mixtures is considered.

Preferential Solvation of a Hydrophobic Probe in Binary Mixtures Comprised of a Nonprotic and a Hydroxylic Solvent: A View of Solute−Solvent and Solvent−Solvent Interactions

“…Preferential solvation (PS) occurs when the polar solute has in its microenvironment more molecules of one solvent than the other in comparison with the bulk composition. This concept is relevant because it allows us to explain spectroscopic, − equilibrium, − and kinetic data ,− for mixed solvents. Preferential solvation commonly results from specific (e.g., hydrogen-bonding) 11 and nonspecific (dielectric enrichment) 12 solute−solvent interactions.…”

Reinforced macromolecular micelle-crosslinked hyaluronate gels induced by water/DMSO binary solvent

“…1b and c. As observed from the digital photos in Fig. 1b [21][22][23] And the structure of the water cluster is broken down particularly when the molar fraction of DMSO is ∼0.35 (the volume fraction of DMSO: ∼0.68). [24][25][26][27] Such a dehydration process thus restricts the swelling of FH gels.…”

DMSO‐Assisted K3PO4‐Catalyzed Cooperative Metal‐Free, Base‐Free Etherification of Chloroheteroarenes at Low Temperature

“…A clear difference in the δ values obtained in DMSO-d 6 and CDCl 3 for both 4-methoxyphenol & nbutanol suggest the enhancement of the acidic nature of the -OH proton assisted by DMSO through S=O lone pair coordination (Scheme 3 and for NMRs see supporting information that gives a comparison between DMSO & CDCl 3 ). [14,15] However, DMSO on its own cannot promote the given transformation and certainly a cooperative effect with K 3 PO 4 could be envisaged as rather than acting as a base, screening studies have suggested a more catalytic or promoting role for K 3 PO 4 (10-20 mol % rather than equivalent amount). Several reports in literature also support this analogy for K 3 PO 4 to exhibit a catalytic role and provide the necessary surface for enhancing further the acidity of the -OH through a weak P=O lone pair coordination (not soluble in DMSO).…”