Heterogeneous Bifunctional Catalysts for the Synthesis of Chiral Vicinal Diols

Heterogeneous bifunctional catalysts consisting of palladate–osmate and osmate–tungstate developed by the ion exchange on quaternary ammonium salts covalently bound to resin, and their homogeneous bimetallic analogs are evaluated for the synthesis of chiral vicinal diols. The heterogeneous bifunctional catalyst (resin-PdOs) and its homogeneous analog are used in the tandem Heck-asymmetric dihydroxylation (AD) to afford diols with excellent yields and enantiomeric excesses (ee's) in the presence of various co-oxidants. The other bifunctional catalyst (resin-OsW) and its homogeneous analog are used in a simultaneous asymmetric dihydroxylation-N-oxidation of a wide range of olefins to obtain chiral vicinal diols with higher yields and ee's using H₂O₂ as terminal oxidant. The bifunctional resin catalysts are recovered quantitatively by a simple filtration and reused for a number of cycles with consistent activity.     

Cloning and sequence analysis of the estA gene encoding enzyme for producing (R)-beta-acetylmercaptoisobutyric acid from Pseudomonas aeruginosa 1001

The estA gene encoding the enzyme that catalyzes the production of (R)-beta-acetylmercaptoisobutyric acid from (R,S)-ester from Pseudomonas aeruginosa 1001, was cloned in Escherichia coli and its nucleotide sequence was determined, revealing the presumed open reading frame encoding a polypeptide of 316 amino acid residues (948 nucleotides). The overall A + T and C + G compositions were 32.59% and 67.41%, respectively. The amino acid sequence of the estA gene product showed a significant similarity with that of the triacylglycerol lipase from Psychrobacter immobilis (38% identity), triacylglycerol lipase from Moraxella sp. (36% identity), and two forms of carboxyl esterases from Acinetobacter calcoaceticus (17% and 17% identities). The deduced amino acid sequences have a pentapeptide consensus sequence, G-X-S-X-G, having an active serine residue, and another active site, dipeptides H-G, located at 70-100 amino acids upstream of the G-X-S-X-G consensus sequence.     

Cloning and Sequence Analysis of the estA gene encoding enzyme for producing (R)-β-acetylmercaptoisobutyric acid from Pseudomonas aeruginosa 1001

The estA gene encoding the enzyme that catalyzes the production of (R)-β-acetylmercaptoisobutyric acid from (R,S)-ester from Pseudomonas aeruginosa 1001, was cloned in Escherichia coli and its nucleotide sequence was determined, revealing the presumed open reading frame encoding a polypeptide of 316 amino acid residues (948 nucleotides). The overall A+T and C+G compositions were 32.59% and 67.41%, respectively. The amino acid sequence of the estA gene product showed a significant similarity with that of the triacylglycerol lipase from Psychrobacter immobilis (38% identity), triacylglycerol lipase from Moraxella sp. (36% identity), and two forms of carboxyl esterases from Acinetobacter calcoaceticus (17% and 17% identities). The deduced amino acid sequences have a pentapeptide consensus sequence, G-X-S-X-G, having an active serine residue, and another active site, dipeptides H-G, located at 70–100 amino acids upstream of the G-X-S-X-G consensus sequence.     

An Improved Process for Selective Liquid-Phase Air Oxidation of Toluene

An improved process for the oxidation of toluene to obtain benzaldehyde and benzyl alcohol with high selectivities using a Co/Mn/Br^– composite catalytic system in liquid phase is described. A protocol for recovery and reuse of the composite catalyst is developed. The use of low concentrations of composite catalytic systems aimed at minimizing corrosion of the reaction, and higher concentrations of toluene affording higher productivity and recyclability of the catalyst giving high turnover number, are the remarkable achievements of the present methodology. Investigation into the recycle, aging and spectroscopic studies of the catalytic system improves the understanding of the process, chemistry and mechanism of the reaction. As the market demand for each product fluctuates, the dynamic system developed here to meet changing demands is very important to obtain one of the products in excess quantities with a change of the ratio of Br^–/Cl^–.     

MCM-41 Anchored Cinchona Alkaloid for Catalytic Asymmetric Dihydroxylation of Olefins: A Clean Protocol for Chiral Diols Using Molecular Oxygen

MCM-41 anchored 1,4-bis(9-O-quininyl)phthalazine (MCM-(QN)₂PHAL)-OsO₄, is prepared for the first time and used in the heterogeneous asymmetric dihydroxylation of olefins to afford diols with good to excellent enantiomeric excesses in the presence of N-methylmorpholine N-oxide, K₃Fe(CN)₆ or molecular oxygen as cooxidants.     

The weathering characteristics of coking coals: Use of a gas flow test in assessing weathering propensity

A study was made of the weathering characteristics of three Australian coking coals in both experimental stockpiles and the laboratory. A gas-flow test was used to assess the relative weathering propensities of these coals in the laboratory under accelerated weathering conditions. The principle of the test is that the pressure drop of a stream of nitrogen gas flowing through a coal sample during continuous heating is a function of the coal's coking propensity. The test results were found to reflect the rate of deterioration in coke strength due to weathering in experimental stockpiles leading to the possibility of using the test to detect oxidized coal. It was also found that the relative weathering propensity of coal did not necessarily increase as the particle size decreased.     

Modeling of Ordered Structures of Phase-Stabilized Cubic Bismuth Oxides

Stabilized bismuth oxides undergo a decay in conductivity when subjected to annealing at temperatures of <600°C, because of the formation of an ordered superstructure, which is observed in transmission electron microscopy (TEM) diffraction patterns. Neutron-diffraction studies of the aged samples indicate that there is a displacement of almost all the anions, from the regular 8c sites to interstitial 32f sites. Based on the TEM patterns and the displacement of the oxygen ions, various structural models for the superstructure have been analyzed. From this work, it can be deduced that the observed decay in conductivity is due to the ordering of the oxygen sublattice, along with a possible concomitant ordering of cations.     

Learning: Student-centred vs teacher-centred

The paper differentiates student centred learning from teacher centred learning, identifies the continuum of factors which contributes to these and provides a self evaluation questionnaire to enable one to judge the extent to which one is ‘teacher-centred’ or ‘student-centred’ in their approach to student learning.