Radical copolymerization of chlorotrifluoroethylene with 4‐bromo‐3,3,4,4‐tetrafluorobut‐1‐ene

The radical copolymerization of chlorotrifluoroethylene (CTFE) with 3,3,4,4‐tetrafluoro‐4‐bromobut‐1‐ene (BTFB) initiated by tert‐butylperoxypivalate is presented. The microstructures of the obtained copolymers are determined by means of NMR spectroscopies and elemental analysis and show that random copolymers were obtained. A wide range of poly(CTFE‐co‐BTFB) copolymers is synthesized, containing from 17 to 89 mol % of CTFE. In all the cases, CTFE is the less reactive of both comonomers. T_d^10% values, ranging from 163 up to 359 °C, are dependent on the BTFB content. These variations of thermal property are attributed to the increase in the number of C‐H and C‐Br bonds breakdown when the BTFB molar percentage in the copolymer is higher. T_g values range from 19 to 39 °C and a decreasing trend is observed when increasing the amount of BTFB in the copolymer. This observation arises from the higher flexibility of the copolymer when increasing the number of fluorobrominated lateral chains. These original fluoropolymers bearing reactive pendant bromo groups are suitable candidates for various applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1714–1720     

N-isopropylsulfinylimines as useful intermediates in the synthesis of chiral amines: expeditive asymmetric synthesis of the calcimimetic (+)-NPS R-568

An efficient and high-yielding approach for the asymmetric synthesis of calcimimetic (+)-NPS R-568 (1) has been developed. The key step of the synthesis is the highly diastereoselective addition of methyl Grignard to the (SS,E)-N-(3-methoxybenzylidene)-2-propanesulfinamide [5(S)], which afforded a single diastereoisomer in high yield in short reaction time.     

Isobaric metabolite interferences and the requirement for close examination of raw data in addition to stringent chromatographic separations in liquid chromatography/tandem mass spectrometric analysis of drugs in biological matrix

In addition to matrix effects, common interferences observed in liquid chromatography/tandem mass spectrometry (LC/MS/MS) analyses can be caused by the response of drug-related metabolites to the multiple reaction monitoring (MRM) channel of a given drug, as a result of in-source reactions or decomposition of either phase I or II metabolites. However, it has been largely ignored that, for some drugs, metabolism can lead to the formation of isobaric or isomeric metabolites that exhibit the same MRM transitions as parent drugs. The present study describes two examples demonstrating that interference caused by isobaric or isomeric metabolites is a practical issue in analyzing biological samples by LC/MS/MS. In the first case, two sequential metabolic reactions, demethylation followed by oxidation of a primary alcohol moiety to a carboxylic acid, produced an isobaric metabolite that exhibits a MRM transition identical to the parent drug. Because the drug compound was rapidly metabolized in rats and completely disappeared in plasma samples, the isobaric metabolite appeared as a single peak in the total ion current (TIC) trace and could easily be quantified as the drug since it was eluted at a retention time very close to that of the drug in a 12-min LC run. In the second example, metabolism via the ring-opening of a substituted isoxazole moiety led to the formation of an isomeric product that showed an almost identical collision-induced dissociation (CID) MS spectrum as the original drug. Because two components were co-eluted, the isomeric product could be mistakenly quantified and reported by data processing software as the parent drug if the TIC trace was not carefully inspected. Nowadays, all LC/MS data are processed by computer software in a highly automated fashion, and some analysts may spend much less time to visually examine raw TIC traces than they used to do. Two examples described in this article remind us that quality data require both adequate chromatographic separations and close examination of raw data in LC/MS/MS analyses of drugs in biological matrix.     

Fast search algorithms for computational protein design

One of the main challenges in computational protein design (CPD) is the huge size of the protein sequence and conformational space that has to be computationally explored. Recently, we showed that state‐of‐the‐art combinatorial optimization technologies based on Cost Function Network (CFN) processing allow speeding up provable rigid backbone protein design methods by several orders of magnitudes. Building up on this, we improved and injected CFN technology into the well‐established CPD package Osprey to allow all Osprey CPD algorithms to benefit from associated speedups. Because Osprey fundamentally relies on the ability of to produce conformations in increasing order of energy, we defined new strategies combining CFN lower bounds, with new side‐chain positioning‐based branching scheme. Beyond the speedups obtained in the new ‐CFN combination, this novel branching scheme enables a much faster enumeration of suboptimal sequences, far beyond what is reachable without it. Together with the immediate and important speedups provided by CFN technology, these developments directly benefit to all the algorithms that previously relied on the DEE/ combination inside Osprey* and make it possible to solve larger CPD problems with provable algorithms. © 2016 Wiley Periodicals, Inc.     

A sensitive nitrite sensor using an electrode consisting of reduced graphene oxide functionalized with ferrocene

A composite consisting of chitosan containing azidomethylferrocene covalently immobilized on sheets of reduced graphene oxide was drop-casted on a polyester support to form a screen-printed working electrode that is shown to enable the determination of nitrite by cyclic voltammetry and chronoamperometry. Both reduction and oxidation of nitrite can be accomplished due to the high electron-transfer rate of this electrode. Under optimal experimental conditions (i.e. an applied potential of 0.7 V vs. Ag/AgCl in pH 7.0 solution), the calibration plot is linear in the 2.5 to 1450 μM concentration range, with an ~0.35 μM limit of detection (at a signal-to-noise ratio of 3). The sensor was successfully applied to the determination of nitrite in spiked mineral water samples, with recoveries ranging between 95 and 101 %.

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Graphical abstract We describe the design of ferrocene-functionalized reduced graphene oxide electrode and its electrocatalytic properties towards the determination of nitrite. Compared to a reduced graphene oxide electrode, the sensor exhibits enhanced electrocatalytic activity towards both oxidation and reduction of nitrite.

     

Synthesis and characterization of polyesters derived from sebacic acid,hexanediol, and hydroquinone

Oils and fats derived from animals and plants provide a good renewable source for polymer precursors. In this investigation, fatty acids derived from plant oils and diols were used as monomers to produce polyesters by melt polycondensation. Sebacic acid, hexanediol, and hydroquinone were used as precursors in the polymer synthesis. The polymers were characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, three-bending point flexural test, X-ray diffraction, tensile testing, and contact angle. The resulting polyesters were blended with epoxies to create materials with an increased elongation at break without affecting other mechanical properties.     

Theoretical calculation of the low laying electronic states of the molecule NaCs with spin-orbit effect

The potential energy curves have been calculated for the 59 lowest electronic states of the molecule NaCs including the spin-orbit effect within the range of 4.5a(0)-20.0a(0) of the internuclear distance R. Using an ab initio method, the calculation is based on a nonempirical pseudopotentials which take into consideration the spin-orbit effect. Gaussian basis sets have been used for both atoms, and the spin-orbit effects have been taken into consideration. The spectroscopic constants have been calculated for 56 electronic states. The components of the spin-orbit splitting have been identified for the states (1,2,4)(3)Pi. The comparison of the present results with those available in the literature shows a very good agreement.     

Non perturbative approach for a polar and polarizable linear molecule in an inhomogeneous electric field: Application to molecular beam deviation experiments

A non perturbative approach is used to solve the problem of a rigid linear molecule with both a permanent dipole moment and a static dipole polarizability, in a static electric field. Eigenenergies are obtained and compared to perturbative low field and high field approximations. Analytical expressions for the orientation parameters and for the gradient of the energy are given. This non perturbative approach is applied to the simulation of beam deviation experiments in strong electric field. Results of simulations are given for inhomogeneous alkali dimers. For LiNa, the simulations are compared to experimental data. For LiK, deviation profiles have been simulated in order to prepare future experiments on this molecule. Received 21 July 1999 and Received in final form 22 September 1999     

Pickering emulsion polymerization of polyaniline/LiCoO2 nanoparticles used as cathode materials for lithium batteries

The oil in water (o/w) emulsions were prepared using aniline dissolved in toluene and LiCoO₂ particles as stabilizers (Pickering emulsions). Pickering emulsions are stabilized by adsorbed solid particles instead of emulsifier molecules. The mean droplet diameter of emulsions was controlled by the mass ratio M (oil)/M (solid particles). The emulsions showed great stability during 3 days. The composite materials containing LiCoO₂ and the conductive polymer polyaniline (PANI) have been prepared by means of polymerization of aniline emulsion stabilized by LiCoO₂ particles. The composite materials were characterized by nanosphere and nanofiber-like structures. The nanofiber-like morphology of the powdered material was distinctly different of the morphologies of the parent materials. The electrochemical reactivity of PANI/LiCoO₂ composites as positive electrode in a lithium battery was examined during lithium ion deinsertion and insertion by galvanostatic charge–discharge testing; PANI/LiCoO₂ (1:4) composite materials exhibited the best electrochemical performance by increasing the reaction reversibility and capacity compared to that of the pristine LiCoO₂ cathode. The first discharge capacity of PANI/LiCoO₂ (1:4) was 167 mAh/g, while that of LiCoO₂ was136 mAh/g.