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.     

Estimation of cysteine and cystine at mercury pool electrode

Zusammenfassung Zum Ausgleich der starken Sogdifferenzen bei Wasserstrahlpumpen als Folge erheblich schwankender Wasserdrucke wird eine automatisch arbeitende Unterdruckregulierung beschrieben. Der dadurch erzielte konstante Nutzsog kommt im Laboratorium all den, Versuchsanordnungen zugute, die einen konstanten Unterdruck benötigen.     

HPLC-Bestimmung von S-Carboxymethyl-l-cystein in Haarwaschmitteln

Zusammenfassung S-Carboxymethyl-l-cystein läßt sich mit o-Phthaldialdehyd/Mercaptoethanol derivatisieren und mittels HPLC an einer LiChrosorb RP-8-Säule unter Verwendung eines Fluorescenzdetektors quantitativ bestimmen. Die Spezifität des Fluorescenzsignals und die gewählten chromatographischen Bedingungen gestatten, ohne spezielle Aufarbeitung der Proben zu arbeiten. Die Standardabweichung beträgt ± 1,1 mg/l bei einem mittleren Gehalt von 98 mg/l.

---

Determination of S-carboxymethyl-l-cysteine in shampoo by HPLC

Summary S-Carboxymethyl-l-cysteine can be determined quantitatively by derivatisation with o-phthaldialdehyde/mercaptoethanol using HPLC with a LiChrosorb RP-8 column and a fluorescent detector. The specifity of the fluorescent signal and the Chromatographic conditions allow to work without any special preparation of the sample. The standard deviation is ± 1.1 mg/l for an average content of 98 mg/l.

     

A simple method for extracting both active oily and water soluble extract (WSE) from Nigella sativa (L.) seeds using a single solvent system

The current study provides a way of extraction for both active NSO and WSE from Nigella sativa seeds using 98% methanol. About 1?kg of ground seeds was macerated by 1:2.5 w/v (g/mL) for 72?hours. After rotary evaporation and 7 days of continuous drying and chilling at 50 and 4?°C, NSO and WSE were obtained at the same instant. Solubility tests of 24 solvents and 11 thin layer chromatographic analyses while 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging assay of NSO (73.66) , WSE (33.32) and NSO?+?WSE (78.22) against ascorbic acid (IC50?=?4.28?mg/mL) was performed. WSE was found to be highly soluble in water and 5% NaOH exhibiting the same Rf value of 0.95 for EtOH:DMSO (9:1) against the honey. WSE has revealed more than twofold higher anti-oxidant activity than others. Formulation of WSE with Tualang honey may provide better targeted hydrophilic drug delivery systems.