Catalytic effects of hydrogen-bond acceptor solvent on nucleophilic aromatic substitution reactions in non-polar aprotic solvent: reactions of phenyl 2,4,6-trinitrophenyl ether with amines in benzene-acetonitrile mixtures

The effect of addition of small amounts of hydrogen-bond acceptor solvent, acetonitrile, to the benzene medium of the reactions of phenyl 2,4,6-trinitrophenyl ether with aniline and cyclohexylamine, respectively have been investigated. The addition produced similar effects in the two reactions—continuous rate increase with increasing amounts of acetonitrile. The results are interpreted in terms of the effect of amine-solvent interaction on the nucleophilicity of the amines and are in accord with our expectations based on the effects observed for hydrogen-bond donor solvent, methanol on the same reactions. It is also established from the results that the role of hydrogen-bond acceptor co-solvent could be played by an added more basic non-nucleophilic amine.     

Composition and antioxidant activities of leaf and root volatile oils of Morinda lucida

Morinda lucida (L.) Benth. (Rubiacae) is used in traditional medicine in many West African countries for the treatment of various human diseases. The leaves and roots of this plant were subjected to hydro-distillation to obtain volatile oils which were analyzed by high resolution GC/MS. Fifty compounds were identified in the leaf volatile oil and the major compounds were alpha-terpinene (17.8%) and beta-bisabolene (16.3%). In the root oil, 18 compounds were identified, the major constituents being 3-fluoro-p-anidine (51.8%) and hexadecanoic acid (12.0%). Antioxidant activities of the oils were examined using the DPPH, ABTS, reducing power and lipid peroxidation assays. All assays were concentration dependent with varying antioxidant potentials. The antioxidant activity of the root volatile oil of M. lucida was similar to that of the standard drugs used.     

Energy analysis of a domestic refrigerator system with ANN using LPG/TiO2–lubricant as replacement for R134a

Journal of Thermal Analysis and Calorimetry - This paper experimentally investigated and also modeled using artificial neural networks (ANN) approach the energy analysis of a domestic refrigerator...     

Photochromic property of ternary transition metal oxide nanocomposite prepared with co-solvated deep eutectic mixtures

Research on Chemical Intermediates - The application of deep eutectic solvents (DES) in the synthesis of photochromic transition metal oxide (TMO)-based nanocomposites is gaining attention in...     

Intermediate and ion-pair formation in the outer-sphere reactions between azido-pentacyanocobaltate(III) and iron(II) polypyridyl complexes in aqueous medium

The kinetics of the reactions between azido-pentacyanocobaltate(III), Co(CN)₅N₃ ³⁻, and iron(II) polypyridyl complexes, Fe(LL)₃ ²⁺ (LL = bipy, phen), have been studied in both neutral and acidic aqueous solutions at I = 0.1 mol dm⁻³ NaCl. The reactions were carried out under pseudo-first-order conditions in which the concentration of Fe(LL)₃ ²⁺ was kept constant, and the second-order rate constants obtained for the reactions at 35 °C were within the range of 0.156–0.219 dm³ mol⁻¹ s⁻¹ for LL = bipy and 0.090–0.118 dm³ mol⁻¹ s⁻¹ for LL = phen. Activation parameters were measured for these systems. The dependence of reaction rates on acid was studied in the range [H⁺] = 0.001–0.008 mol dm⁻³. The reaction in acid medium shows interesting kinetics. Two reactive species were identified in acid medium, namely, the protonated cobalt complex and the azido-bridged binuclear complex. The electron-transfer process is proposed to go by mixed outer- and inner-sphere mechanisms in acid medium, in which electron transfer through the bridged inner-sphere complex (k ₅) is slower than through the outer-sphere path (k ₄). Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Robust solvent‐free fabrication and characterization of (polydimethylsiloxane‐co‐2‐hydroxyethylmethacrylate)/poly (ethylene glycol) methacrylate (PDMS‐HEMA)/PEGMA hydrogels

Combining hydrophobic materials such as polydimethylsiloxane (PDMS), a natural hydrophobic material with typical hydrophilic monomers without using organic solvent remains a big challenge due to their extreme different properties; hence, fabricating a class of silicone hydrogels with two extremes without use of organic solvents could bring us a novel class of silicone hydrogels. Herein, a range of PDMS‐HEMA‐PEGMA hydrogels was prepared from hydroxyl‐terminated PDMS, 2‐hydroxyethylmethacrylate (HEMA), poly (ethylene glycol) methacrylate (PEGMA), and isophorone diisocyanate via condensation and radical copolymerization reactions. The infrared results confirmed the PDMS‐HEMA‐PEGMA network formation, while the hydrophilicity of the as‐prepared block copolymer was dependent on (PDMS‐HEMA)/PEGMA ratio. Increasing the PEGMA content resulted in increased equilibrium water content, phase separation, surface roughness, and tensile strength, while the tensile modulus, elongation at break, optical transmittance, water contact angle, and oxygen permeability (Dk) were decreasing. At PEGMA content of 28.3%, the relative protein adsorption ratio decreased to 20% and 36% for bovine serum albumin and lysozyme, respectively, compared with that of the control (PDMS‐HEMA), suggesting antiprotein adsorption ability. In overall, the results showed that the PDMS‐HEMA‐PEGMA hydrogels not only exhibited remarkable hydrophilicity and suppressed protein adsorption but also maintained higher optical transparency and oxygen permeability (Dk).     

Experimental performance of a safe charge of LPG refrigerant enhanced with varying concentrations of TiO2 nano-lubricant in a domestic refrigerator

Journal of Thermal Analysis and Calorimetry - This paper presents an experimental investigation of energy consumption and heat transfer performance characteristics of a safe mass–charge of...     

Ligand substitution and reduction reactions of decakis(isopropylisocyanide)dicobalt(II)

The reactions between decakis(isopropylisocyanide)dicobalt(II), present as [Co(CNCHMe₂)₅]²⁺ in solution, and three triaryl phosphines, PPh₃, P(C₆H₄Me-p)₃, and P(C₆H₄OMe-p)₃, have been studied in dichloromethane. The reactions were investigated under pseudo first-order conditions at different temperatures. A combination of conventional, stopped-flow, and infrared spectroscopy was employed in order to gain insight into the reaction mechanisms. Addition of each of the three phosphines to the Co(II) complex results in a shift in the λ _max followed by increase and/or decrease in absorbance at the new wavelength. The triaryl phosphines react in the order P(C₆H₄OMe-p)₃ ? P(C₆H₄Me-p)₃ > PPh₃. This is explained in terms of the electron-donating/π-acceptor properties of the phosphines. The reactions are proposed to proceed via a number of reaction pathways including ligand substitution, ligand rearrangement, disproportionation, and reduction.