The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Ning Zhao - One of the best experts on this subject based on the ideXlab platform.
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efficient Propylene Carbonate synthesis from Propylene glycol and carbon dioxide via organic bases
Catalysis Communications, 2008Co-Authors: Shiyong Huang, Junping Li, Ning ZhaoAbstract:Abstract Organic bases were first used as effective catalysts for the synthesis of Propylene Carbonate from Propylene glycol and carbon dioxide in the presence of acetonitrile. Acetonitrile in the reaction acted as not only the solvent but also the dehydrating reagent to remove the water produced from the reaction. It was interesting that upon ammonium Carbonate being introduced into the reaction system, the catalytic selectivity was significantly enhanced. With 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the catalyst, the yield of Propylene Carbonate could reach 15.3% with the selectivity of 100% under the optimal conditions.
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catalytic performance of metal oxides for the synthesis of Propylene Carbonate from urea and 1 2 propanediol
Journal of Molecular Catalysis A-chemical, 2007Co-Authors: Qibiao Li, Ning ZhaoAbstract:Abstract The influences of acid–base properties of metal oxides on the catalytic performance for synthesis of Propylene Carbonate from urea and 1,2-propanediol was investigated, and the reaction was stepwise. The amphoteric ZnO showed the best activity, and the yield of Propylene Carbonate reached 98.9%. The urea decomposition over oxides was characterized by using FTIR. ZnO, CaO, MgO and La 2 O 3 were favorable to promote urea decomposition to form the isocyanate species, and the formation of isocyanate species was the key to urea alcoholysis. The catalytic activity of urea decomposition was consistency to the catalytic performance for synthesis of Propylene Carbonate. Based on these, the probable reaction mechanism was proposed.
Marta Omedespujol - One of the best experts on this subject based on the ideXlab platform.
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catalytic asymmetric cyanohydrin synthesis in Propylene Carbonate
Tetrahedron Letters, 2009Co-Authors: Michael North, Marta OmedespujolAbstract:Propylene Carbonate can be used as a green solvent for asymmetric cyanohydrin synthesis catalyzed by VO(salen)NCS. A range of 10 aromatic and aliphatic aldehydes gave high enantioselectivities (up to 93%) and conversions (up to 100%) in reactions carried out at or near room temperature with reaction times of 24 h or less.
Michael North - One of the best experts on this subject based on the ideXlab platform.
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Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in Propylene Carbonate
Beilstein Journal of Organic Chemistry, 2010Co-Authors: Michael North, Marta Omedes-pujolAbstract:Propylene Carbonate can be used as a green solvent for the asymmetric synthesis of cyanohydrin trimethylsilyl ethers from aldehydes and trimethylsilyl cyanide catalysed by VO(salen)NCS, though reactions are slower in this solvent than the corresponding reactions carried out in dichloromethane. A mechanistic study has been undertaken, comparing the catalytic activity of VO(salen)NCS in Propylene Carbonate and dichloromethane. Reactions in both solvents obey overall second-order kinetics, the rate of reaction being dependent on the concentration of both the aldehyde and trimethylsilyl cyanide. The order with respect to VO(salen)NCS was determined and found to decrease from 1.2 in dichloromethane to 1.0 in Propylene Carbonate, indicating that in Propylene Carbonate, VO(salen)NCS is present only as a mononuclear species, whereas in dichloromethane dinuclear species are present which have previously been shown to be responsible for most of the catalytic activity. Evidence from 51V NMR spectroscopy suggested that Propylene Carbonate coordinates to VO(salen)NCS, blocking the free coordination site, thus inhibiting its Lewis acidity and accounting for the reduction in catalytic activity. This explanation was further supported by a Hammett analysis study, which indicated that Lewis base catalysis made a much greater contribution to the overall catalytic activity of VO(salen)NCS in Propylene Carbonate than in dichloromethane.
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catalytic asymmetric cyanohydrin synthesis in Propylene Carbonate
Tetrahedron Letters, 2009Co-Authors: Michael North, Marta OmedespujolAbstract:Propylene Carbonate can be used as a green solvent for asymmetric cyanohydrin synthesis catalyzed by VO(salen)NCS. A range of 10 aromatic and aliphatic aldehydes gave high enantioselectivities (up to 93%) and conversions (up to 100%) in reactions carried out at or near room temperature with reaction times of 24 h or less.
Shiyong Huang - One of the best experts on this subject based on the ideXlab platform.
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efficient Propylene Carbonate synthesis from Propylene glycol and carbon dioxide via organic bases
Catalysis Communications, 2008Co-Authors: Shiyong Huang, Junping Li, Ning ZhaoAbstract:Abstract Organic bases were first used as effective catalysts for the synthesis of Propylene Carbonate from Propylene glycol and carbon dioxide in the presence of acetonitrile. Acetonitrile in the reaction acted as not only the solvent but also the dehydrating reagent to remove the water produced from the reaction. It was interesting that upon ammonium Carbonate being introduced into the reaction system, the catalytic selectivity was significantly enhanced. With 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the catalyst, the yield of Propylene Carbonate could reach 15.3% with the selectivity of 100% under the optimal conditions.
John D Holbrey - One of the best experts on this subject based on the ideXlab platform.
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intermolecular structure and hydrogen bonding in liquid 1 2 Propylene Carbonate and 1 2 glycerol Carbonate determined by neutron scattering
Physical Chemistry Chemical Physics, 2017Co-Authors: Yoan Delavoux, Mark Gilmore, Martin P Atkins, Malgorzata Swadźbakwaśny, John D HolbreyAbstract:Neutron diffraction with isotopic substitution has been used to investigate the liquid structures of Propylene Carbonate and glycerol Carbonate. C–H⋯OC hydrogen-bonding motifs dominate the local structure of Propylene Carbonate, giving rise to the formation of head-to-tail correlated chains of molecules. In contrast, glycerol Carbonate exhibits a more disordered structure with no overall dominant interactions in which the pendant hydroxyl function disrupts structure-making correlations present in Propylene Carbonate.
