The acid dissociation constants of the hydroxyl groups in 25, 26, 27, 28-tetrahydroxy-5, 11, 17, 23-tetrasulphonic-calix[4]arene (SC4) were determined at 25οC by a combination of potentiometric and spectrophotometric titration method. The first and second acid dissociation constants (pKa1, pKa2) were found to be 3.19 and 12.1, which demonstrated pKa shift due to intramolecular hydrogen bonding ...

according to the bronsted definition, any compound which has a hydrogen atom is an acid, since itmay be lost as a proton. a thermodynamical cycle is proposed to calculate absolute pka values forbronsted acids in aqueous solution. the equilibrium of dissociation of a bronsted acid depends onthe interaction of the acid and its conjugate base with solvent molecules. there fore the pka valuedepends...

The purpose of this study was to determine the acid dissociation constants (pKa) of meloxicam in the presence of various surfactants including sodium lauryl sulfate (SLS) as an anionic surfactant, cetyltrimethylammonium bromide (CTAB) as a cationic surfactant and Triton® TX-100 (TX-100) as a non-ionic surfactant in different pre-determined concentrations. The related pKa was determined spec...

In this research complexation of dioxovanadium(V) with nitrilotriacetic acid (NTA) at differentionic strengths (0.1 to 1.0 mol dm-3) of sodium perchlorate as supporting electrolyte and pH rangeof 1.00-2.50 at 25 °C has been investigated by a combination of potentiometric and UVspectrophotometric measurements. Stability constants of two species, V0211L- and VO2H2L havebeen calculated. Ionic stre...

in this research complexation of dioxovanadium(v) with nitrilotriacetic acid (nta) at differentionic strengths (0.1 to 1.0 mol dm-3) of sodium perchlorate as supporting electrolyte and ph rangeof 1.00-2.50 at 25 °c has been investigated by a combination of potentiometric and uvspectrophotometric measurements. stability constants of two species, v0211l- and vo2h2l havebeen calculated. ionic stre...