Showing papers on "Acetonitrile published in 1989"

Femtosecond resolved solvation dynamics in polar solvents

Abstract: The transient solvation of a polar fluorescent probe has been studied by the time resolved Stokes shift technique with roughly five times shorter time resolution than previously reported. New shorter time components in the solvation relaxation function C(t) have been discovered for methanol, propionitrile, and propylene carbonate; the C(t) function for acetonitrile is singly exponential within the limitations of the instrument. The observed C(t) has been compared to theoretical calculations using the dielectric continuum (DC) model for each solvent, with non‐Debye expressions for the solvent dielectric response. For methanol the DC model predictions agree closely with experiment. For the polar aprotic solvents propylene carbonate and propionitrile, the shape of the experimental decay is different from the DC predictions, but the average decay times 〈τs〉 are closer to the DC predictions than previously reported. The comparison of theory and experiment is clearly limited by the inconsistencies and limited f...

Basicity of substituted 2-phenyl-1,1,3,3- tetramethylguanidines and other bases in acetonitrile solvent

Abstract: A series of 30 phenyl substituted derivatives of 2-phenyl-1,1,3,3-tetramethylguanidine was synthesized and the pKa value of each was measured in acetonitrile using a conventional, general purpose g...

Solvation of anion radicals: gas-phase versus solution

Abstract: Reversible half-wave potentials for 38 neutral/anion radical couples have been measured at 298 K by cyclic voltammetry in five solvents: tetrahydrofuran, N,N-dimethylformamide (DMF), acetonitrile, dimethyl sulfoxide, and methanol. Among the compounds are 22 substituted nitrobenzenes and nine quinones. The potentials are referenced to the cobaltocenium/cobaltocene couple

Degradation of Acetonitrile by Pseudomonas putida.

Abstract: A bacterium capable of utilizing high concentrations of acetonitrile as the sole source of carbon and nitrogen was isolated from soil and identified as Pseudomonas putida. This bacterium could also utilize butyronitrile, glutaronitrile, isobutyronitrile, methacrylonitrile, propionitrile, succinonitrile, valeronitrile, and some of their corresponding amides, such as acetamide, butyramide, isobutyramide, methacrylamide, propionamide, and succinamide as growth substrates. Acetonitrile-grown cells oxidized acetonitrile with a Km of 40.61 mM. Mass balance studies with [14C]acetonitrile indicated that nearly 66% of carbon of acetonitrile was released as 14CO2 and 14% was associated with the biomass. Metabolites of acetonitrile in the culture medium were acetic acid and ammonia. The acetate formed in the early stages of growth completely disappeared in the later stages. Cell extracts of acetonitrile-grown cells contained activities corresponding to nitrile hydratase and amidase, which mediate the breakdown of actonitrile into acetic acid and ammonia. Both enzymes were intracellular and inducible and hydrolyzed a wide range of substrates. The specific activity of amidase was at least 150-fold higher than the activity of the enzyme nitrile hydratase.

Reductive Addition of CO 2 to 9,10‐Phenanthrenequinone

Abstract: Reduction chimique de la phenanthrenequinone-9,10 par ajout d'un groupe carbonyle Etude de la reaction par voltammetrie cyclique dans un electrolyte acetonitrile-tetrafluoroborate d'ammonium tetrabutyle

Proton-coupled electron transfer in [(bpy)2Mn(O)2Mn(bpy)2]3+

Abstract: Etude des reactions electrochimiques du complexe de manganese sur une electrode de carbone a l'etat vitreux dans de l'acetonitrile

Asymmetric synthesis of optically active β-substituted ketones by highly enantioselective catalytic conjugate addition of dialkylzinc reagents to enones using a catalyst system of nickel(II)-chiral ligand–achiral ligand in acetonitrile/toluene

Abstract: Highly enantioselective conjugate addition of dialkylzinc reagents to aryl substituted enones using Ni(II)-bipyridyl–chiral ligand in acetonitrile (MeCN)/toluene as an in situ prepared catalyst system affords β-substituted ketones in up to 90% enantiomeric excess (ee)

Oxygen atom transfer chemistry of heteropolytungstate 'browns' in nonaqueous solvents

Abstract: Etude sur les composes XW 9 VI O 37 W 3 IV (OH 2 ) 3 n− (X=H 2 , B ou Si) en solution de toluene ou d'acetonitrile

Potential dependence of the relative conductivity of poly(3-methylthiophene): electrochemical reduction in acetonitrile and liquid ammonia

Abstract: Relevant topics for Chemistry of Materials include both theoretical and experimental studies that focus on the preparation, characterization, processing, or understanding of materials with unusual or useful properties. Of particular importance are the originality, significance, overall quality, and completeness of the work as well as its relevance to both chemistry and materials science. The last of these considerations, in particular, serves to define the particular focus of this journal and the special niche that it seeks to fill among periodicals in materials science. Recognizing the international scope and the breadth of the subject, the Editorial Advisory Board of Chemistry of Materials has been selected to ensure a strong international representation as well as a broad perspective on the wide range of subjects in materials chemistry. Included on the Advisory Board are over sixty scientists and engineers from academic, industrial, and governmental laboratories in ten different countries. The articles scheduled for publication in the first few issues are illustrative of this broad, international perspective on materials chemistry. Among the topics covered are molecular and polymeric conductors, nonlinear optical materials, thin-film resists, various aspects of solid-state inorganic chemistry including high-T, superconductors, sol-gel processing, chemical vapor deposition, ceramic precursors, biosensors, colloid chemistry, electronic materials processing, heterogeneous

Model reactions for nitrogen fixation. Photo-induced formation and X-ray crystal structure of [Os2(NH3)8(MeCN)2(N2)]5+ from [OsVI(NH3)4N]3+

Abstract: UV-VIS irradiation of an acetonitrile solution of [OsVI(NH3)4N](CF3SO3)3 and organic donors under degassed conditions gave [Os2(NH3)8(MeCN)2(N2)]5+; the X-ray crystal structure of the µ-dinitrogen complex has been determined and the Os–N(N2) distances found to be 1.873(9) and 1.893(9)A.

Voltammetric Characterization of α- and β-Dodecamolybdophosphates in Aqueous Organic Solutions

Abstract: The electrochemical properties of α- and β-dodecamolybdophosphates were characterized at the glassy carbon (GC) electrode. It was found that the β-isomer was only stable in neat organic solvents. When molybdophosphate was prepared in aqueous organic solutions, a mixture of α- and β-isomers formed.

Ion transport in pyrrole-based polymer films

Abstract: Ionic resistivities and counterion diffusion coefficients for polypyrrole, poly-[1-methyl-3-(pyrrol-1-ylmethyl)pyridinium](poly-MPMP+) and pyrrolex-[Ru(2,2′-bipyridine)2(3-(pyrrol-1-ylmethyl) pyridine)Cl]+ copolymer films have been obtained by chronoamperometry using the single-pore model. For poly-MPMP+ both the electronic resistivity and the ionic resistivity can be simultaneously determined. Finite-difference simulations have been used to confirm the validity of the equations used and to extend the applicability of the model.Counterion diffusion coefficients in polypyrrole and poly-MPMP+ have also been determined by rotating-disc voltammetry and d.c. conductivity measurements. Where possible the results have been confirmed by the use of two independent methods. Diffusion coefficients for I–, Cl–, ClO4– and Fe(CN)64– in the above polymers in water and/or acetonitrile are compared and discussed. It is concluded that: (a) polypyrrole and poly-MPMP+ are solvated and swollen to a much greater extent in water than in acetonitrile, (b) permanent cationic sites increase the permeability of polypyrrole in water but not in acetonitrile and (c) the permeability of polypyrrole in acetonitrile can be increased by the incorporation of bulky metal complexes.

Kinetics of the bis(2,9-dimethyl-1,10-phenanthroline)copper(I/II) self-exchange reaction in solution

Abstract: The rate of the Cu(dmp) 2 +/2+ electron-transfer reaction has been measured by 1 H NMR spectroscopy in the perdeuterated solvents water (with the chloride salts), acetonitrile, and acetone (with the CF 3 SO 3 − salts)

The bonding of acetonitrile and CH2CN on Ag(110) determined by near edge x-ray absorption fine structure: evidence for π-donor bonding and azimuthal ordering

Abstract: Carbon K edge near edge x‐ray absorption fine structure (NEXAFS) spectra of adsorbed acetonitrile and reactive intermediates derived therefrom on Ag(110) were studied in order to determine their orientation and bonding to the surface. For both the multilayer and the adsorbed monolayer there is excellent agreement between the spectra of the adsorbed acetonitrile and the gas phase species. For the multilayer coverage the orientation of the acetonitrile molecules is not completely random; the molecules prefer an orientation with their bond axes closer to parallel than perpendicular to the surface. At monolayer coverage acetonitrile bound to the surface is unrehybridized. It is bound with its linear molecular skeleton parallel to the surface and randomly oriented azimuthally. Annealing molecular CH3 CN to 325 K in the presence of coadsorbed atomic oxygen produces a linear CH2 CN surface intermediate, the molecular axis of which is parallel to the surface and perpendicular to the close‐packed direction. The C–...

Electrochemistry of Tris(β-diketonato)ruthenium(III) Complexes at Platinum Electrodes in Nonaqueous Solutions and Substituent Effects on Their Reversible Half-Wave Potentials

Abstract: The one-electron oxidation and reduction processes at platinum electrodes of a series of β-substituted and γ-substituted tris(β-diketonato)ruthenium(III) complexes are studied in acetonitrile, N,N-dimethylformamide, and nitromethane solutions, each containing 0.1 mol dm−3 (C2H5)4NClO4 at 25 °C. Syntheses of three new γ-substituted derivatives are described. Attempts to isolate the immediate product of the one-electron oxidation of [Ru(acac)3] in acetonitrile failed; bis(acetonitrile)bis(acetylacetonato)ruthenium(III) was obtained instead. Diffusion coefficients of the complexes in the acetonitrile medium are presented. The reversible half-wave potentials for the oxidation and the reduction in the acetonitrile medium depended linearly on the sum of the Hammett constants of the substituents (σp for the β-substituents and σm for the γ-substituents). Analysis of the dependence of the half-wave potentials on several kinds of substituent parameters suggests that the inductive effect is operative at both the β-p...

Solvent relaxation in electron-transfer reactions: comparisons between Barrier-crossing dynamics in water and polar aprotic media

Abstract: : Rate constants, k sub ex, for electron self exchange of three metallocene redox couples, carboxymethyl (cobaltocenium-cobaltocene) CpCO2Me2) 2Co+o, hydroxymethyl (ferrocenium-ferrocene) (Cp (dot) CpCH2OH)Fe+/o, and trimethylaminomethyl (ferrocenium-ferrocene) (Cp (dot) CpCH2NMe3)Fe2+/2, obtained using proton NMR line broadening, are utilized along with optical electron-transfer energies for the mixed-valence biferrocenylacetylene cation to obtain solvent-dependent frequencies, (Kappa sub el)(n sub n), in water relative to those in methanol and six aprotic solvents. While (Kappa sub el)(n sub n) for the ferrocene couples is insensitive to the solvent, indicative of nonadiabatic behavior (K sub el < 1), K sub el (n sub n) vn for the cobaltocene couple is responsive to the solvent dynamics. While rapid barrier-crossing dynamics are obtained in water, comparable to acetonitrile, acetone, and nitromethane, the influence of high-frequency relaxation components in water is less marked than for methanol. Keywords: Nuclear: Magnetic resonance: Metallocene redox couples: Line broadening: Biferrocenylacetylene cation: Aprotic solvents: Solvent dynamics: Mixed valence.

The reactive state in the photo-rearrangement of o-nitrobenzaldehyde

Abstract: The primayy step of the o-nitrobenzaldehyde-o-nitrosobenzoic acid photorearrangement in solution has been studied by flash absorption with 35 ps 355 nm light pulses. Flash photolysis of o-nitrobenzaldehyde in acetonitrile or THF solutions produces a transient absorption with a maximum at ca. 440 nm. Formation of the transient was < 35 ps, the laser pulse width, and within experimental error, no furthrr buildup was observed. The transient which decayed at nanosccond times is attributed to a remarkably reactive ketene intermediate formed by H abstraction of the aldehydic hydrogen by the excited state of the nitro group. Decay of the ketene was more rapid in water-acetonitrile, methanol-acetonitrile, tert-butyl alcohol and in THF than in acetonitrile solution. It is suggested that the intramolecular reaction of the ketene intermediate is enhanced in THF relative to acetonitrile because of the ability of THF to faciliaate proton transfer associated with the reaction.