Kinetics of the thermal decomposition of bis(trifluoromethyl) peroxydicarbonate,CF3OC(O)OOC(O)OCF3

Thermal decomposition of bis(trifluoromethyl) peroxydicarbonate has been studied. The mechanism of decomposition is a simple bond fission, homogeneous first‐order process when the reaction is carried out in the presence of inert gases such as N₂ or CO. An activation energy of 28.5 kcal mol^?1 was determined for the temperature range of 50–90°C. Decomposition is accelerated by nitric oxide because of a chemical attack on the peroxide forming substances different from those formed with N₂ or CO. An interpretation on the influence of the substituents in different peroxides on the O? O bond is given. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 15–19, 2003     

Capillary isoelectric focusing of proteins utilizing poly(vinylpyrrolidone)- and plexiglas-coated columns

Fused-silica capillaries chemically derivatized with silane/poly(vinylpyrrolidone) (PVP) or dynamically modified with plexiglas [poly(methyl methacrylate)] were prepared and evaluated with regard to column stability and separation performance for capillary isoelectric focusing of standard proteins. The PVP coating showed the better stability and was good for at least 100 runs while the plexiglas coating started to deteriorate after about 30 runs. The time spent for the plexiglas coating is about 40 minutes while the PVP coating requires two days. The migration time reproducibility was better with the PVP capillary (RSD 0.7-1.6%, n = 5) compared to the plexiglas-coated column (RSD 1.2-2.9%, n = 5) while peak area and height varied over a similar interval (RSD 2-28.1% area; 0.9-22.7% height, n = 5). The two most consistent proteins in this evaluation, viz. myoglobin A and carbonic anhydrase II, showed linear dynamic ranges between 5-150 and 5-50 microg/mL, and limits of detections at 2 and 1 microg/mL, respectively, employing UV detection at 280 nm.     

Synthesis and characterization of trifluoromethyl fluoroformyl peroxycarbonate,CF3OC(O)OOC(O)F

The synthesis of CF(3)OC(O)OOC(O)F is accomplished by the photolysis of a mixture of (CF(3)CO)(2)O, FC(O)C(O)F, CO, and O(2) at -15 degrees C using a low-pressure mercury lamp. The new peroxide is obtained in pure form in low yield after repeated trap-to-trap condensation and is characterized by NMR, IR, Raman, and UV spectroscopy. Geometrical parameters were studied by ab initio methods [B3LYP/6-311+G(d)]. At room temperature, CF(3)OC(O)OOC(O)F is stable for many days in the liquid or gaseous state. The melting point is -87 degrees C, and the boiling point is extrapolated to 45 degrees C from the vapor pressure curve log p = 8.384 - 1715/T (p/mbar, T/K). A possible mechanism for the formation of CF(3)OC(O)OOC(O)F is discussed, and its properties are compared with those of related compounds.     

Efficient synthesis in three steps and spectral determination of methyl‐5‐[(o‐, m‐, and p‐substituted‐phenylthio]‐2‐benzimidazolecarbamates

The preparation and spectral properties often novel methyl 5‐[(o‐, m‐, and p‐substituted)‐phenylthio]‐2‐benzimidazolecarbamates with possible pharmacological activity as antihelmintics is described; by condensation and cyclization between 5‐methylthioures sulfate chloroformic acid methyl ester and 3,4‐diaminophenyl‐substituted‐phenylthio ether dissolved in ethanol. The structures of all final products were corroborated by ir; ¹H‐nmr, ¹³C‐nmr and ms.     

Sodiation Of Hard Carbon: How Separating Enthalpy And Entropy Contributions Can Find Transitions Hidden In The Voltage Profile

Sodium-ion batteries (NIBs) utilize cheaper materials than lithium-ion batteries (LIBs) and can thus be used in larger scale applications. The preferred anode material is hard carbon, because sodium cannot be inserted into graphite. We apply experimental entropy profiling (EP), where the cell temperature is changed under open circuit conditions. EP has been used to characterize LIBs; here, we demonstrate the first application of EP to any NIB material. The voltage versus sodiation fraction curves (voltage profiles) of hard carbon lack clear features, consisting only of a slope and a plateau, making it difficult to clarify the structural features of hard carbon that could optimize cell performance. We find additional features through EP that are masked in the voltage profiles. We fit lattice gas models of hard carbon sodiation to experimental EP and system enthalpy, obtaining: 1. a theoretical maximum capacity, 2. interlayer versus pore filled sodium with state of charge.     

Stability of general relativistic static thick disks: the isotropic Schwarzschild thick disk

We study the stability of general relativistic static thick disks. As an application we consider the thick disk generated by applying the “displace, cut, fill and reflect” method, usually known as the image method, to the Schwarzschild metric in isotropic coordinates. The isotropic Schwarzschild thick disk obtained from this method is the simplest model to describe, in the context of General Relativity, real thick galaxies. Stability under a general first order perturbation of the disk energy momentum tensor is investigated. The first order perturbation, when applied to the conservation equations, leads to a set of differential equations that have fewer equations than unknowns. In this article we search for perturbations in which the perturbation of the four velocity in a certain direction leads to a pressure perturbation in the same direction. We found that, in general, the isotropic Schwarzschild thick disk is stable under these kinds of perturbations.