Voltammetric behavior of triethylamine trihydrofluoride and anisole in acetonitrile as a first approach of studies for electro-fluorination of some adducts

This work focuses on kinetic studies of anisole and triethylamine trihydrofluoride (fluorinating agent) on platinum electrode and acetonitrile as solvent, in order to get a better understanding of their anodic behavior. Results show that both compounds can be oxidized and some kinetic parameters are calculated: the diffusion coefficient within the working media, the anodic electronic transfer coefficient and the apparent intrinsic heterogeneous electronic transfer constant. An unusual variation of these parameters occurs within the chosen reaction conditions, particularly by varying the triethylaminetrihydrofluoride concentration. Preliminary experiments for anodic fluorination of dimethoxy ethane (DME) and anisole were carried out and even if results show a possible electrofluorination for the DME (classically used as solvent), there is no fluorination of anisole when electrochemical microreactor was used

A DFT study of the G3-Factor and derivatives

We present theoretical studies of the G3-Factor and two derivatives, the methylated (G3Me) and the fluorinated (G3F) endoperoxides. These endoperoxides were previously tested as alternative drugs against the parasite causing malaria. They showed promisin activity.The geometry of each compound was optimized in its lowest singlet and triplet spin states at the B3LYP/6-311G* level of theory. It was followed by a NBO analysis. The ground state of the G-Factors is a singlet. The geometric parameters found by the DFT calculations are in agreement with available experimental results. The spin density distribution for the triplet state shows a biradical molecule. The singlet–triplet splitting is of 36.60, 33.96 and 34.09 kcal/mol (B3LYP/6-311G*) and of 36.07, 33.51 and 33.60 kcal/mol (B3LYP/6-311++G**) for the G3-Factor and the G3Me and G3F derivatives, respectively

Comparison of diffusivities data of streptocyanine dyes by electrochemical and NMR-DOSY methods

Diffusivity data of streptocyanine dyes in acetonitrile were investigated using both transient voltammetric techniques and NMR-DOSY. Results of voltammetric measurements allow determination of the diffusion coefficient D values in the range of 1.2-1.6 x 10-9 m² s-1 for the target dyes. Deuterated acetonitrile solvent was used for NMR-DOSY experiments and diffusivities of streptocyanines are given after calibration of acetonitrile on its tracer diffusion value of D∗ACN of 4.37 x 10-⁹. The results for the two methods appear to be in good agreement allowing use of the convenient NMR-DOSY method to measure diffusivity of streptocyanine dyes at low concentrations and so giving a direct access to the number of exchanged electrons using limiting current electrochemical techniques. This last method affords a great advantage of obtaining diffusion coefficients by non-electrochemical method

Design and optimization of electrochemical microreactors for continuous electrosynthesis

The study focuses on the design and construction, as well as the theoretical and experimental optimization of electrochemical filter press microreactors for the electrosynthesis of molecules with a high added value. The main characteristics of these devices are firstly a high-specific electrochemical area to increase conversion and selectivity, and secondly the shape and size of themicrochannels designed for a uniform residence time distribution of the fluid. A heat exchanger is integrated into the microstructured electrode to rapidly remove (or supply) the heat required in exo- or endothermic reactions. The microreactors designed are used to perform-specific electrosynthesis reactions such as thermodynamically unfavorable reactions (continuous NADH regeneration), or reactions with high enthalpy changes

Reductive dimerization mechanisms of some streptocyanine dyes

Cyclic voltammetric studies of streptocyanine dyes were carried out on a glassy carbon electrode. For dye electroreduction, logarithmic analysis of the convoluted current indicates an EC2 mechanism with dimerization following electron transfer. Relevant kinetic and thermodynamic values are reported

New reaction of formation of the fused tricyclic bispyrroloquinone ring system

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A combined spin trapping/EPR/mass spectrometry approach to study the formation of a cyclic peroxide by dienolic precursor autoxidation

International audienceThe spontaneous addition of air oxygen to a dienolic compound, yielding a cyclic peroxide, was followed by spin trapping (ST) combined with EPR spectroscopy and mass spectrometry (MS). Using two different nitrones, the ST/EPR study allowed the detection of the spin adduct of a radical intermediate, and the radical centre in the addend was identified after similar experiments performed with two different (13)C-labelled analogues of the substrate. The media were also submitted to electrospray ionisation, in both positive and negative modes, for structural characterisation of the spin adducts by tandem mass spectrometry. This allowed the structure of the hydroxylamine derivatives of the nitroxides formed to be identified. Following these results, a mechanism pathway was proposed for this autoxidation

Ene-reaction between a dienolic compound and 2-methyl-2-nitrosopropane: an EPR-MS study

International audienceThe combination of electron paramagnetic resonance (EPR) and mass spectrometry (MS) was used as an efficient tool to elucidate the mechanism of an ene-reaction between a dienol compound and 2-methyl-2-nitrosopropane. (C) 2010 Elsevier Ltd. All rights reserved

5-Hydroxy-2,2,6,6-tetramethyl-4-(2-methylprop-1-en-yl)cyclohex-4-ene-1,3 -dione, a novel cheletropic trap for nitric oxide EPR detection

International audienceThe title compound behaves as an efficient cheletropic trap for both NO and NO(2) radicals in the presence of oxygen, yielding EPR observable nitroxide and alkoxynitroxide, respectively