Hydrolysis of diphenylmethyltin(iv) chloride in different aqueous solutions of ethanol

The hydrolysis of [(Ph)₂MeSn(IV)]⁺ has been studied spectrophotometrically at 25ˆC and constant ionic strength of 0.1 mol dm⁻³ sodium perchlorate. Over a wide pH range, 1–11, the investigation has been performed in different aqueous solutions of ethanol. The species formed together with their formation constants have been determined using the computer program Squad. The hydrolysis constants at different media were analyzed in terms of Kamlet and Taft's parameters. A single‐parameter correlation of the formation constants, K_1‐1 and K_1‐2, versus α (hydrogen‐bond donor acidity), β (hydrogen‐bond acceptor basicity), and π^* (dipolarity/polarizability) for both cases are relatively poor in all solutions, but multiparameter correlation represents significant improvement with regard to the single‐parameter models. In this work, we have also used the normalized polarity parameter, E, alone and in combination with the Kamlet–Taft's parameters to find a better correlation of the formation constants in different aqueous solutions of ethanol. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:654–660, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20484     

Interaction of Dioxovanadium(V) with Alanine, Alanylalanine, and Alanylglycine

The stability constants of the systems dioxovanadium(V) with alanylalanine, alanylglycine, and alanine have been determined in aqueous solution in 0.8 pH 5 at 25°C and 0.1 mol-dm^–3 (NaClO₄), using a combination of potentiometric and spectrophotometric techniques. The compositions of the formed complexes were determined and it was shown that dioxovanadium(V) forms two mononuclear 1:1 and 1:2 species with alanine of the type VO₂L and VO₂L₂ ^–, and two mononuclear 1:1 complexes with alanylpeptides of the type VO₂HL and VO₂L^–.     

Ionic strength dependence of formation constants, complexation of nitrilotriacetic acid with tungsten(VI) ion

The dependence on ionic strength of protonation of nitrilotriacetic acid and its complexation with W(VI) is reported in sodium perchlorate, sodium nitrate and sodium chloride solutions as background salts. The measurements have been performed at 25°C and various ionic strengths in the range 0.1–1.0 mol dm⁻³, using a combination of potentiometric and spectrophotometric techniques. The overall analysis of the present and the previous data dealing with the determination of stability constants at different ionic strengths allowed us to obtain a general equation, by which a formation constant determined at a fixed ionic strength can be calculated, with a good approximation, at another ionic strength, if 0.1 ≤ ionic strength ≤ 1.0 mol dm⁻³ sodium perchlorate, sodium nitrate or sodium chloride.     

A strain rate dependent yield criterion for isotropic polymers: Low to high rates of loading

In this study, strain rate sensitivity of yield behavior in a semicrystalline polymer, Nylon 101, was experimentally investigated. A precise definition of yield was established for the polymer by deforming several specimens to certain levels of strain and measuring the residual strains after unloading and strain recovery. The material was then subjected to different loading conditions (uniaxial to multiaxial) at four different quasi-static and intermediate strain rates to determine several points on the material's yield loci. Due to positive strain rate sensitivity of this polymer, the material's yield loci expanded uniformly as the strain rates were increased to higher values. Further, an empirical hydrostatic pressure dependent yield equation (with four material constants) was developed to simulate these behaviors as a function of strain rate. The capability of the developed criterion was examined by simulating high strain rate yield behavior of the material in tension and in compression. The simulation results revealed very good correlations/predictions between the experimental data and the responses determined from the proposed yield criterion.