The protonation equilibria of four substituted N-methylbenzenesulfonamides, X-MBS: X = 4-MeO (3a), 4-Me (3b), 4-Cl (3c) and 4-NO(2) (3d), in aqueous sulfuric acid were studied at 25 °C by UV-vis spectroscopy. As expected, the values for the acidity constants are highly dependent on the electron-donor character of the substituent (the pK(BH+) values are -3.5 ± 0.2, -4.2 ± 0.2, -5.2 ± 0.3 and -6....

the formation constants of the species formed in the systems fr + glycine + dioxovanadium(v) + and h+ + glycine have been determined in aqueous solutions of methanol at 25 °c and constant ionicstrength, using spectrophotometric and potentiometric techniques. it was shown thatdioxovanadium(v) forms two mononuclear 1 : land 1:2 complexes with glycine. the formationconstants in various media were ...

the complexation reactions between diacetyl monooxime (damo), imidazole (him), histamine (hist) and histidine (his) with co2+, ni2+ and cu2+ were studied potentiometrically in aqueous solution at 25 °c and m= 0.5 m kno3. the overall stability constants log b's of species were obtained by computer refinement of ph-volume data using best computer program. several models were tested and, based on ...

A novel synthesis of 3-fold symmetric, homochiral tris(2-alkyl-2-aminoethyl)amine (TREN) derivatives is presented. The synthesis is general in scope, starting from readily prepared chiral alpha-amino aldehydes. The optical purity of the N-BOC protected derivatives of tris(2-methyl-2-aminoethyl)amine and tris(2-hydroxymethyl-2-aminoethyl)amine has been ascertained by polarimetry and chiral NMR c...

The complexation of Cd2+ by diallyl disulfide (DADS) and diallyl sulfide (DAS) has been studied by differential pulse voltammetry. Stability constants, (log β), of the 1:1 (PbL) and 1:2 (PbL2) complexes, where L = ligand, were found to be in the range of ca. 5.8 - 6.2 and 9.6 -10.6, respectively. Complex formation is accompanied with a significant decrease in the peak current and the shift of t...

The complexation reactions of some transition metal ions and 2-aminopyridine (2-ampy) were studied potentiometrically in aqueous solution at µ=0.1 M and 25 °C. The overall stability constants log β’s of all species are obtained by computer refinement of pH-volume data with using the BEST computer program. Several models were tested and the best one accepted according to the least sum of squ...

Mixed dissociation constants of four drug acids, i.e. silychristin, silybinin, silydianin and mycophenolate at various ionic strengths I of range 0.01 and 0.30 and at temperatures of 25 and 37 ◦C were determined using the SQUAD(84) regression analysis program applied to pH-spectrophotometric titration data. The proposed strategy of an efficient experimentation in a protonation constants determi...

Three novel chelators based on the 6-amino-6-methylperhydro-1,4-diazepine scaffold and possessing three pendant N-acetic or N-α-methylacetic acid have been synthesised. The ligands contain six donor atoms for complexation of Mn(II) ions and thus potentially leave an additional site for coordination of a water molecule. The protonation constants of the ligands and the stability constants of thei...

The acid-base properties of N,N9-disubstituted dithiooxamides derived from alkyl-a-aminoacids or glycylglycine were studied in aqueous solutions of pH 2.5-10.8. For each dithiooxamide, protonation constants were obtained from potentiometric data for three dilute aqueous solutions [I50.15 M (NaClO ), 37.08C] using the program HYPERQUAD, and are reported as conventional pK values. For 4 a compoun...