Experimental and Computational Study of the Thermal Decomposition of 3‐Methyl‐3‐buten‐1‐ol in m‐Xylene Solution

An experimental study of the thermal decomposition of a β‐hydroxy alkene, 3‐methyl‐3‐buten‐1‐ol, in m‐xylene solution, has been carried out at five different temperatures in the range of 513.15–563.15 K. The temperature dependence of the rate constants for the decomposition of this compound in the corresponding Arrhenius equation is given by ln k (s^?1) = (25.65 ± 1.52) ? (17,944 ± 814) (kJ·mol^?1)·T^?1. A computational study has been carried out at the M05–2X/6–31+G(d,p) level of theory to calculate the rate constants and the activation parameters by the classical transition state theory. There is a good agreement between the experimental and calculated rate constants and activation Gibbs energies. The bonding characteristics of reactant, transition state, and products have been investigated by the natural bond orbital analysis, which provides the natural atomic charges and the Wiberg bond indices. Based on the results obtained, the mechanism proposed is a one‐step process proceeding through a six‐membered cyclic transition state, being a concerted and slightly asynchronous process. The results have been compared with those obtained previously by us (Struct Chem 2013, 24, 1811–1816) for the thermal decomposition of 3‐buten‐1‐ol, in m‐xylene solution. We can conclude that in the compound studied in this work, 3‐methyl‐3‐buten‐1‐ol, the effect of substitution at position 3 by a weakly activating CH₃ group is the stabilization of the transition state formed in the reaction and therefore a small increase in the rate of thermal decomposition.     

Structural and Kinetic Aspects of Blood Plasma Protein Adsorption on the Surface of Hydrophobic Polymers

Abstract

Due to the wide use of polymers in medicine, researchers are required to solve a very important problem–to understand the interaction between materials of nonphysiological origin and the surrounding biological liquids, and tissues, particularly blood.     

Tunneling estimates of paramagnon suppression of superconductivity in transition metals

New experimental estimates are given of the separate electron-phonon (λ_ph) and paramagnon (λ_S) contributions to mass renormalization for the transition metals Nb and V, from recent tunneling results. Our analysis, which is the first of its kind, is based on the recent demonstration of Daams, Mitrovic, and Carbotte of a simple rescaling of the Eliashberg equations using an effective coupling parameter $\text{λ}{}_{\mathrm{ph}}\text{(1+λ}{}_{\mathrm{S}}\text{)}$. The results provide a consistent picture of superconductivity in these transition elements from tunneling, in substantially improved agreement with other measurements. We conclude that spin fluctuations reduce the electron-phonon T_c values in Nb and V by 25% and 45%, respectively.     

Quantitative proximity tunneling spectroscopy

Using the new Green's function calculation of Arnold and an appropriate modification of the McMillan-Rowell procedure, it is demonstrated that tunneling characteristics of suitable proximity junctions may be inverted to determine the properties of superconductors which do not oxidize satisfactorily. The junctions employed are of the form M-Al₂O₃-Al/S (where S is the superconductor of interest). The Al thickness is less than 100 Å and the Al/S interface is specularly transmitting. Quantitative values for Δ_S(E) and Δ_N(E) are obtained for S=Nb, N=Al.