ChemInform Abstract: SCHEINBARE IONENPRODUKTE UND ACIDITAETSNIVEAUS VON METHANOL‐DIMETHYLSULFOXID‐ UND METHANOL‐N,N‐DIMETHYL‐ACETAMID‐GEMISCHEN

Autoprotolysis Constants of Water–N-Methylacetamide Mixtures. A New Application of the Hammett Relationship to Acidity Constants

“…This situation is similar to one previously encountered in the methanol-DMSO mixtures (14), but different to that observed in the case of water-DMSO mixtures because of the weaker basicity of DMSO (9-1 1). Table 1 The selection of acids to be used for preparing buffer solutions is conditioned by the wish to obtain in each mixed solvent an acidity scale as extended as possible, with the differences between the pS+ values of successive buffers not greater than 0.5 p K unit.…”

“…Water-NMA Mixtures In pure NMA, the hydrogen electrode can be used to indicate the activity of the solvated proton (12), so that we have made use of a method which has already proved adequate for many solvent mixtures (7,13,14 f i (Fig. 1) justifies the approximation of the mean activity coefficient f, by the simplified Debye-Hiickel expression : log f, E -B 3 On the other hand, the measurement acidity of the buffer solutions shows that under our operating conditions (same ionic strength I in the compartments containing the hydrogen electrode) the junction potentials E,, and Ej,, are identicaL2 Table 1 gives the extrapolated pKs values.'…”

σ-Complexes as biochemical and biophysical probes. Part 6. The interaction of N-2,4,6-trinitrophenyl-L-lysine with methoxide ion in dimethylsulfoxide-methanol (95%-5% v/v) mixture: proton transfer and σ-complex formation

“…carboxylic acids and phenols) acids in water and DMSO. Generally speaking [22][23][24][25][26][27][28][29] , the change from water to DMSO for a given acid usually results in a decrease in the acid strength of both acid types, an effect that is often greater for uncharged acids than for positively charged ones 22 . In some cases, mild increases in the acid strength of positively charged acids have been noted 22 .…”

Multivariate analysis of data for the ionization of weak acids in water – dimethyl sulfoxide solvent mixtures

“…Subanalyses of data set 4 were then performed to investigate the possibility that one-component models might describe sets which are more homogeneous with respect to compound types (sets 6,8) or solvents (set 5). This was not the case; A = 2 was required (but sufficient) for these subsets also.…”

“…Halle, Schaal, et al (8)(9)(10)12) showed that p(,Ka) varies with solvent composition, and that different classes of compounds behave differently. In the present paper we apply the methods of principal components (pc) analysis (13)(14)(15)(16) to the p(,Ka) values reported by them for 41 weak acids, listed in Table 1, in ten water-DMSO solvent mixtures, listed in Table 2.…”