Production and properties of a biosurfactant obtained from a member of the Bacillus subtilis group (PTCC 1696)

The production and properties of a biosurfactant, synthesized by a member of the Bacillus subtilis group (PTCC 1696) which was isolated from an Iranian oil field, have been investigated. The biosurfactant, which was produced as a primary metabolite associated with the growth of PTCC 1696, was able to reduce the surface and interfacial tension of media to 26.7 and 0.1 mN/m, respectively. Crude biosurfactant and acid precipitated biosurfactant have critical micelle concentrations of 10 and 100 mug/ml, respectively. The stability of the biosurfactant at different salinities, pH and temperature and also its emulsifying activity have been investigated. It is an effective surfactant at very low concentrations over a wide range of temperatures, pHs and salt concentrations and also has the ability to emulsify oil, which is essential for enhanced oil recovery.     

New synthetic route towards 2,2‐dimethylchromene and synthesis of substituted 7‐(dimethylpropargyl)chromene

Trifluoromethansufonic acid (TFA) was found a proper reagent for regioselectively ring closure of resorcinol to afford 7‐hydroxy‐2,2‐dimethyl‐2,3‐dihydrochromen‐4‐one 3 . The propargylation of 3 gave rise to 2,2‐dimethyl‐7‐(2‐methylbut‐3‐yn‐2‐yloxy)‐2,3‐dihydrochromen‐4‐one 4 . Condensation of 4 with substituted phenyl or benzyl Grignard reagents afforded substituted phenyl or benzylidene chromenes 6a‐d and 4‐(substitutedbenzylidene)‐3,4‐dihydro chromenes 8a‐e , respectively.     

Trimethylsilylation of Hydroxyl Group with 1,1,1,3,3,3‐Hexamethyldisilazane (HMDS) Catalyzed by Tribromomelamine (TBM)

Tribromomelamine (TBM) can be used as a novel catalyst for the trimethylsilylation of alcohols and phenols with 1,1,1,3,3,3‐hexamethyldisilazane (HMDS). A wide variety of hydroxyl groups were selectively protected in CH₂Cl₂/CH₃CN under mild conditions.     

Stripping Voltammetry of Cerium(IIl) with a Chemically Modified Carbon Paste Electrode Containing Functionalized Nanoporous Silica Gel

This research introduces the design of an adsorptive stripping voltammetric method for the cerium(III) determination at a carbon paste electrode, chemically modified with dipyridyl‐functionalized nanoporous silica gel (DPNSG‐CPE). The electroanalytical procedure comprised two steps: the Ce(III) chemical accumulation at ?200 mV followed by the electrochemical detection of the Ce(III)/dipyridyl complex, using anodic stripping voltammetry. The factors, influencing the adsorptive stripping performance, were optimized including the modifier quantity in the paste, the electrolyte concentrations, the solution pH and the accumulation potential or time. The resulting electrode demonstrated a linear response over a wide range of Ce(III) concentration (1.0–28 ng mL^?1). The precision for seven determinations of 4 and 10 ng mL^?1 Ce(III) was 3.2% and 2.5% (relative standard deviation), respectively. The prepared electrode was used for the cerium determination in real samples and very good recovery results were obtained.     

Evidence for a tetraoxo intermediate in a reaction between a superoxometal complex and acylperoxyl radicals

The superoxo complex Cr aq( (18)O (18)O) (2+) reacts with (CH 3) 3C(O) (16)O (16)O (*) to generate quantitative yields of mixed-label dioxygen, (18)O (16)O, demonstrating that this cross-reaction involves head-to-head interaction between the metal-activated and alkyl-activated dioxygen.     

Palladium supported on diaminoglyoxime‐functionalized Fe3O4 nanoparticles as a magnetically separable nanocatalyst in Heck coupling reaction

A hybrid material of palladium supported on diaminoglyoxime‐functionalized Fe₃O₄ was used as an effective and recyclable catalyst in Mizoroki–Heck coupling reactions. The catalyst was very effective for the Mizoroki–Heck reaction of aryl halides with styrene and conversion was in most cases excellent. The yields of the products were in the range 75–98%. The catalyst showed good stability and could be recovered and reused for six reaction cycles without significant leaching and loss its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.