Methane to higher hydrocarbons via halogenation

Activation of methane with a halogen followed by the metathesis of methyl halide is a novel route from methane to higher hydrocarbons or oxygenates. Thermodynamic analysis revealed that bromine is the most suitable halogen for this goal. Analysis of the published data on the reaction kinetics in a CSTR enabled us to judge on the effects of temperature, reactor residence time and the feed concentrations of bromine and methane to the conversion of methane and the selectivity towards mono or dibromomethane. The analysis indicated that high dibromomethane selectivity is attainable (over 90%) accompanied by high methane conversions. The metathesis of dibromomethane can provide an alternative route to the conversion of methane (natural gas) economically with smaller installations than the current syn-gas route.     

Synthesis and characterization of cyclohexene oxide functional polystyrene macromonomers by ATRP and their use in photoinitiated cationic polymerization

In this study, a novel well-defined macromonomer of epoxy end-functionalized polystyrene was synthesized by atom transfer radical polymerization (ATRP). The compound 3-cyclohexenylmethyl-2-bromopropanoate was synthesized by the condensation of 3-cyclohexene-1-methanol with 2-bromopropanoyl bromide. Subsequently, the epoxidation of the obtained 3-cyclohexenylmethyl-2-bromopropanoate using 3-chloroperoxybenzoic acid results in a new epoxy functional ATRP initiator. The ATRP of styrene (St) in bulk at 110 °C, by means of this initiator in conjunction with the cuprous complex Cu(I)Br/bipyridine, yields a well-defined macromonomer of polystyrene with an epoxy end group. GPC, IR, and ¹H NMR analyses revealed that a low-polydispersity polystyrene with the desired functionality at the end of the chain was obtained. The photoinduced cationic polymerization of this macromonomer yielded graft and block copolymers.     

The survival of E. coli O157:H7, S. Typhimurium and L. monocytogenes in black carrot (Daucus carota) juice

In this study the survival and growth patterns of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in various concentrations of black carrot juice were investigated during incubation period at 4 °C and 37 °C for 7 days. Several parameters, such as juice concentration (%), pH, incubation temperature (°C) and time (days) were found effective on the survival of pathogens tested. Although L. monocytogenes has been found to be the less resistant microorganism to the variable conditions, there were only ca. 1 and 2 log reductions in the number of the cells in the juice samples incubated at 4 °C for 2 and 7 days, respectively. Incubating at low temperature (4 °C) enhanced the survival of test microorganisms.     

Cyclohexene oxide mid‐chain functional macromonomer of poly(ε‐caprolactone): Synthesis,characterization, and photoinitiated cationic homo‐ and copolymerization

In this study, a novel well‐defined epoxy mid‐chain functional macromonomer of poly(ε‐caprolactone) (PCL) has been synthesized by ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) and epoxidation on workup with 3‐chloroperoxybenzoic acid. The ROP of ε‐CL monomer in bulk at 110°C, by means of a dihydroxy functional initiator namely, 3‐cyclohexene‐1,1‐dimethanol in conjunction with stannous‐2‐ethylhexanoate, (Sn(Oct)₂), yielded a well‐defined PCL with a cyclohexene mid‐chain group. The epoxidation of the cyclohexene (CH) mid‐chain group of PCL was performed using 3‐chloroperoxybenzoic acid. GPC, IR, and ¹H‐NMR analyses revealed that a low‐polydispersity macromonomer of PCL with the desired cyclohexene oxide (CHO) functionality at the mid‐chain was obtained. The photoinduced cationic polymerizations of this macromonomer yielded comb‐shaped and graft copolymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Block Copolymers by Using Combined Controlled Radical and Radical Promoted Cationic Polymerization Methods

Summary A novel synthetic procedure for the preparation of block copolymers based on the combination of diphenylethene (DPE) mediated controlled radical polymerization and radical promoted cationic polymerization is described. In the first step, the controlled polymerization of styrene (St) and methyl methacrylate (MMA) in presence of DPE yields polymers with various structures of diphenylethyl units in the main chain. Upon heating these prepolymers undergo scission to give polymeric radicals. Oxidation of these radicals by onium salts such as diphenyliodonium heaxfluorophosphate (Ph₂I⁺PF₆ ⁻) and N-ethoxy-2-methylpyridinium hexafluorophosphate (EMP⁺PF₆ ⁻) yields reactive cations capable of initiating cationic polymerization of cyclohexene oxide (CHO). Block copolymer structure was confirmed by IR and NMR spectral measurements and GPC analysis. Received: 13 December 2002/Revised version: 25 March 2003/ Accepted: 11 March 2003 Correspondence to Yusuf Yagci     

Long-Term Effect of Acidic Beverages on Dental Injectable Composite Resin: Microhardness,Surface Roughness,Elastic Modulus,and Flexural Strength Patterns

Strength of Materials - The purpose of this study is to evaluate the effects of different acidic beverages on the surface roughness, microhardness, flexural strength, and elastic modulus of...     

Bioactive xanthones from the roots of Hypericum perforatum (common St John's wort)

BACKGROUND: Extracts of Hypericum perforatum L. (common St John's wort; Hypericaceae) are sold as phytopharmaceuticals and herbal supplements to treat mild to moderate depression and as food additives. Extensively cultivated in Europe, plants can be infected by anthracnose (Colletotrichum gloeosporioides), a virulent fungal pathogen that causes tissue necrosis and dramatically decreases crop value. Such infections triggered the production of new secondary metabolites, specifically xanthones, in cell culture experiments. RESULTS: Bioassay‐guided fractionation of H. perforatum root extracts, testing for growth inhibition of plant pathogenic fungi from the genera Colletotrichum, Botrytis, Fusarium and Phomopsis, was performed. In vitro anti‐inflammatory activity through inhibition of COX‐1, COX‐2 and 5‐LOX‐catalyzed LTB₄ formation was also evaluated. Extracts were analyzed by various chromatographic means and structure elucidation was performed using data from nuclear magnetic resonance and mass spectrometry. CONCLUSION: Researchers have previously described constituents from the aerial parts of this species, but few reports describe secondary metabolites found in underground parts, of particular interest because the lower stem and upper root are often sites of fungal infection. This work resulted in the isolation of three xanthones: 1,6‐dihydroxy‐5‐methoxy‐4′,5′‐dihydro‐4′,4′,5′‐trimethylfurano‐(2′,3′:3,4)‐xanthone; 4,6‐dihydroxy‐2,3‐dimethoxyxanthone; and cis‐kielcorin, one of which possessed novel bioactivity against species of Phomopsis and inhibited 5‐LOX‐mediated LTB₄ formation. Copyright © 2010 Society of Chemical Industry     

Activated carbon supported silicotungstic acid catalysts for ethyl‐tert‐butyl ether synthesis

Vapor phase ethyl‐tert‐butyl ether (ETBE) production was conducted in the presence of Cesium salts of silicotungstic acid (Cs‐STA), activated carbon supported silicotungstic acid (AC‐STA), and activated carbon supported Cesium salts of silicotungstic acid (AC‐Cs‐STA) catalysts. Isobutene (IB) conversion to ETBE at 373 K were determined as 0.16 and 0.2 for STA and AC‐STA catalysts on constant space time basis. This increase of activity is one of the highlights of this study considering that STA loading in AC‐STA catalysts had been adjusted to 40%. IB conversion to ETBE obtained at 373 K in the presence of AC‐STA catalyst was found to be close to equilibrium. Stability of the synthesized catalysts were tested by applying a washing procedure with ethanol. Repeated ETBE synthesis with thoroughly washed samples indicated quite stable and active catalyts. © 2011 American Institute of Chemical Engineers AIChE J, 2011