THE KINETICS AND MECHANISM OF THE REACTION OF TRICOORDINATE PHOSPHORUS COMPOUNDS WITH SULFENATE ESTERS

Abstract

The kinetics and mechanism of the reaction of tricoordinate phosphorus compounds, Ar_nP(OCH₂CF₃)_3-n with arylsulfenate esters, ArSOCH₂CF₃, are reported. Product analysis, kinetic order, activation parameters, Hammett data and solvent effects are the criteria used to elucidate the two step mechanism involving arylthiophosphoranes as intermediates.     

Exploiting the Structural Metamorphosis of Polymers to ‘Wrap’ Micron-Sized Spherical Objects

There is growing interest in developing methods to ‘wrap’ nano- and micron-sized biological objects within films that may offer protection, enhance their stability or improve performance. We describe the successful ‘wrapping’ of lectin-decorated microspheres, which serve as appealing model micron-sized objects, within cross-linked polymer film. This approach utilizes polymer chains able to undergo a structural metamorphosis, from being intramolecularly cross-linked to intermolecularly cross-linked, a process that is triggered by polymer concentration upon the particle surface. Experiments demonstrate that both complementary molecular recognition and the dynamic covalent nature of the crosslinker are required for successful ‘wrapping’ to occur. This work is significant as it suggests that nano- and micron-sized biological objects such as virus-like particles, bacteria or mammalian cells—all of which may benefit from additional environmental protection or stabilization in emerging applications—may also be ‘wrapped’ by this approach.     

Chemical and Physical Characteristics of Pulsed Electrical Discharge Within Gas Bubbles in Aqueous Solutions

The chemical and physical characteristics of pulsed electrical discharge within gas bubbles immersed in an aqueous solution were investigated using a reactor with long protrusion length high voltage needle electrodes. Argon gas was introduced at the base of the needle electrode causing gas bubbles to flow upwards in contact with the needle. The effects of needle protrusion length were evaluated by using 2, 4, and 6 cm length needles under a wide range of power input (3–78 W). No significant differences in chemical or electrical characteristics were found among the different protrusion lengths. H₂ and H₂O₂ generation rates were proportional to input power and the energy yield efficiency for these species was not affected dramatically by input power. The results of discharge within bubbles in aqueous solution were also compared with those for direct liquid phase discharge and gas phase discharge above the liquid surface.     

A novel oxazolidinone antibiotic: RWJ‐416457

The crystal structure of the antibiotic drug candidate RWJ‐416457 (systematic name: N‐{(5S)‐3‐[4‐(5,6‐dihydro‐2H,4H‐2‐methylpyrrolo[3,4‐c]pyrazol‐5‐yl)‐3‐fluorophenyl]‐2‐oxo‐1,3‐oxazolidin‐5‐yl}acetamide), C₁₈H₂₀FN₅O₃, which belongs to the first new class of antibiotics discovered in the past 30 years, has been determined at 150 K. Each molecule of this drug donates one hydrogen bond to a neighboring molecule and accepts one hydrogen bond to give (O=C—R—N—H...O=C—R—N—H...)_n linkages along the b‐axis direction. The compound contains a pyrrolopyrazole ring, which, owing to its uncommon structure, has been shown to have particular effectiveness against multi‐drug‐resistant bacteria.     

Monitoring oil displacement processes with k‐t accelerated spin echo SPI

Magnetic resonance imaging (MRI) is a robust tool to monitor oil displacement processes in porous media. Conventional MRI measurement times can be lengthy, which hinders monitoring time‐dependent displacements. Knowledge of the oil and water microscopic distribution is important because their pore scale behavior reflects the oil trapping mechanisms. The oil and water pore scale distribution is reflected in the magnetic resonance T₂ signal lifetime distribution. In this work, a pure phase‐encoding MRI technique, spin echo SPI (SE‐SPI), was employed to monitor oil displacement during water flooding and polymer flooding. A k‐t acceleration method, with low‐rank matrix completion, was employed to improve the temporal resolution of the SE‐SPI MRI measurements. Comparison to conventional SE‐SPI T₂ mapping measurements revealed that the k‐t accelerated measurement was more sensitive and provided higher‐quality results. It was demonstrated that the k‐t acceleration decreased the average measurement time from 66.7 to 20.3 min in this work. A perfluorinated oil, containing no ¹H, and H₂O brine were employed to distinguish oil and water phases in model flooding experiments. High‐quality 1D water saturation profiles were acquired from the k‐t accelerated SE‐SPI measurements. Spatially and temporally resolved T₂ distributions were extracted from the profile data. The shift in the ¹H T₂ distribution of water in the pore space to longer lifetimes during water flooding and polymer flooding is consistent with increased water content in the pore space. Copyright © 2015 John Wiley & Sons, Ltd.     

High Speed and Rapid State Switching ESI- TOF- MS Technology and Its Applications

Due to new emerging fast separation technology and the great demand of high sample throughput in discovery, large number of samples now needed to be analyzed by mass spectrometer with high conformation accuracy.     

Hydrogen-bonded oxadiazole mesogens

Hydrogen-bonded analogues of recently reported biaxial nematic oxadiazoles have been prepared. These are obtained by having oxadiazole derivatized with either one or two pyridines, leading either to symmetric or unsymmetric materials complexed using several different benzoic acids. The new materials were studied by optical microscopy and DSC and were found to show N and SmA phases, i.e. mesomorphism characteristic of a calamitic rather than a bent-core mesogen. This mesomorphism is discussed in terms of the flexibility of the complexes and the bend angle at the centre of the complexes.