NOPR Collection:

Electron spin resonance studies on titanium(III) chloride in aqueous 2-methyl- 2-butanol (z-amyl alcohol)

Thu, 01 Nov 1990 00:00:00 GMT

Title: Electron spin resonance studies on titanium(III) chloride in aqueous 2-methyl- 2-butanol (z-amyl alcohol) Authors: Premovic, PI Abstract: On addition of small amounts of water (1% to 2%, v/v) to TiCl₃ (0.02 M, pH 1.4 to 1.8) partially dissolved in t-amyl alcohol, an electron spin resonance signal (g₀ = 1.9589 ± 0.0002) with well-resolved superhyperfine structure due to water protons is observed (the coupling constant equals 0.187 ± 0.003 mT). Confirmation of splitting to be due to water hydrogens has been obtained by using D₂O in equivalent experiments. Aqueous solutions of Ti₂(SO₄)₃, TiBr₃ or TiI₃ (0.01 M to 1.0 M, pH 0.8 to 1.8) saturated with t-amyl alcohol (ca. 5%, v/v) give no electron spin resonance signal. Addition of NaCl or LiCl (1.0 M) to these solutions produces a signal identical in hyperfine pattern and-close in the value of g factor (1.9580±0.0002) to that for TiCl₃ solution. It is proposed that there are axial alkoxide and chloride ions and four equatorial water molecules in the first coordination sphere of this ESR-active Ti(III) complex ion. Approximate spin concentration measurements, made employing deuterated samples, indicate that maximum ESR signal intensity (at ca. 2% added water) represents only 15 ± 5% of the nominal Ti(III) that is present. Page(s): 1039-1044

Effect of the molecular character and extent of crosslinking on the reactivity of attached amino groups in crosslinked polyacrylamide gels

Thu, 01 Nov 1990 00:00:00 GMT

Title: Effect of the molecular character and extent of crosslinking on the reactivity of attached amino groups in crosslinked polyacrylamide gels Authors: Devaky, K S; George, Benny K; Pillai, V N Rajasekharan Abstract: The dependence of the reactivity of the attached amino groups in crosslinked polyacrylamide gels on the extent of crosslinking and the molecular character of the crosslinks has been studied. Acrylamide has been copolymerized with N, N'-methylene-bis-(acrylamide) (NNMBA), tetraethyleneglycol diacrylate (TEGDA) and divinyl benzene (DYB) in different proportions to afford crosslinked polyacrylamide gels of varying nature and extent of crosslinking. These gels have been functionalised with amino groups by treating with excess ethylenediamine. The extent of amino functionalisation is found to be dependent on the nature and degree of crosslinking. The reactivity of amino groups in these polyacrylamide gels has been investigated by following the course of aminolysis of p-nitrophenyl acetate with these resins. These studies reveal a significant influence of the nature and extent of crosslinking on the aminolysis reaction. The polarity of the crosslinking agent and its molar percentage affect the extent of swelling and solvation which are decisive in the facilitation of the aminolysis of the p-nitrophenyl active ester. Page(s): 1045-1049

Conductance behaviour of silver(I) bromate and silver(I) perchlorate in water - N,N-dimethyl formamide mixtures

Thu, 01 Nov 1990 00:00:00 GMT

Title: Conductance behaviour of silver(I) bromate and silver(I) perchlorate in water - N,N-dimethyl formamide mixtures Authors: Giridhar, V V; Kalidas, C Abstract: The conductances of silver(I) bromate and perchlorate in water - N,N-dimethyl formamide (DMF) mixtures have been determined over the entire range of solvent compositions. The data have been analysed by the 1980 Fuoss equation and the limiting molar conductances (˄_o) and ion association constants (K_A) have been evaluated at all solvent compositions. The ˄_o values have been split into their ionic contributions and corresponding Walden products have been evaluated using the transference number data derived from a concentration cell with transference. The Walden product of silver ion decreases sharply with the addition of DMF and this has been interpreted in terms of selective solvation of this ion by DMF. For anions, the Walden product varies in a complex manner and is strongly influenced by solvent-solvent interactions. Page(s): 1050-1054

Equilibrium and transport properties of amino acid solutions: Part 1- Temperature dependence of apparent molar volume in aqueous solutions between 288 and 308 K

Thu, 01 Nov 1990 00:00:00 GMT

Title: Equilibrium and transport properties of amino acid solutions: Part 1- Temperature dependence of apparent molar volume in aqueous solutions between 288 and 308 K Authors: Wadi, Ramesh K; Islam, M N; Goyal, Rma Kant Abstract: Solute apparent molar volumes (ϕ_v) obtained from precise density measurements on aqueous solutions of -ɑ-aminoburync acid, 4-hydroxy--proline, -serine, -phenylalanine, -norleucine, -aminovaleric acid and ω-aminocaprylic acid over the temperature range 288-308 K and the concentration range 0.02-0.33 mol kg^-1 are reported. The derived side chain and end group contributions to the limiting apparent molar volume (ϕ) are also presented. Page(s): 1055-1059