Showing papers on "Acetonitrile published in 2005"
TL;DR: This deposition method, which involves simple reagents and does not require the isolation and purification of the diazonium salt, enabled the grafting of covalently bounded layers which exhibited properties very similar to those of layers obtained by the classical derivatization method involving isolated diaz onium salt dissolved in acetonitrile or aqueous acid solution.
Abstract: The derivatization of a glassy carbon electrode surface was achieved by electrochemical reduction of several in situ generated diazonium cations. The diazonium cations were synthesized in the electrochemical cell by reaction of the corresponding amines with NaNO2 in aqueous HCl. The versatility of the method was demonstrated by using six diazonium cations. This deposition method, which involves simple reagents and does not require the isolation and purification of the diazonium salt, enabled the grafting of covalently bounded layers which exhibited properties very similar to those of layers obtained by the classical derivatization method involving isolated diazonium salt dissolved in acetonitrile or aqueous acid solution. Cyclic voltammetry and electrochemical impedance spectroscopy carried out in aqueous solutions containing electroactive redox probe molecules such as Fe(CN)63-/4- and Ru(NH3)63+ confirmed the barrier properties of the deposited layers. The chemical composition of the grafted layers was d...
350 citations
TL;DR: The transferable potentials for phase equilibria (TraPPE) force fields are extended to amine, nitro, nitrile, and amide functionalities and to pyridine and pyrimidine, with excellent agreement with experimental results.
Abstract: The transferable potentials for phase equilibria (TraPPE) force fields are extended to amine, nitro, nitrile, and amide functionalities and to pyridine and pyrimidine. In many cases, the same parameters for a functional group are used for both united-atom and explicit-hydrogen representations of alkyl tails. Following the TraPPE philosophy, the nonbonded interaction parameters were fitted to the vapor-liquid coexistence curves for selected one-component systems. Coupled-decoupled configurational-bias Monte Carlo simulations in the Gibbs ensemble were applied to neat (methyl-, dimethyl-, trimethyl-, ethyl-, diethyl-, or triethyl-)amine, nitromethane, nitroethane, nitrobenzene, acetonitrile, propionitrile, acetamide, propanamide, butanamide, pyridine, and pyrimidine. Excellent agreement with experimental results was found, with the mean unsigned errors being less than 1% for both the critical temperature and the normal boiling temperature. Similarly, the liquid densities at low reduced temperatures are reproduced to within 1%, and the deviation for the critical densities is about 4%. Additional simulations were performed for the binary mixtures of methylamine + n-hexane, diethyl ether + acetonitrile, 1-propanol + acetonitrile, and nitroethane + ethanol. With the exception of the methylamine/n-hexane mixture for which the separation factor is substantially overestimated, agreement with experiment for the other three mixtures is very satisfactory.
214 citations
TL;DR: In this article, two phosphonium salts such as trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide (IL1) and Trihexyl (tetradescyl) phosphoniamide dicyanamide (IL2) have been used as electrolytes for supercapacitors.
Abstract: Ionic liquids (ILs) have been used as electrolytes for supercapacitors. Two phosphonium salts such as trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide (IL1) and trihexyl(tetradecyl) phosphonium dicyanamide (IL2) have been selected for this target. To decrease the viscosity of ILs, a small amount of acetonitrile (from 5 to 25 wt %) was added. Supercapacitor based on activated carbon (AC) as electrodes and IL1 with 25 wt % of acetonitrile supplied capacitance values of 100F∕g at a high operating voltage of 3.4 V. Such a supercapacitor reached a high energy of ∼40Wh∕kg and a good cyclability.
185 citations
TL;DR: In this article, the density and speed of sound (u) data for 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) + methanol and acetonitrile binary mixtures over the entire range of their compositions were reported.
Abstract: We report the density (ρ) and speed of sound (u) data for 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) + methanol and ([BMIM][PF6]) + acetonitrile binary mixtures over the entire range of their compositions at T = (298.15 to 318.15) K. From these data, excess molar volume and isentropic compressibility deviation values have been calculated and fitted to the fourth-order Redlich−Kister equation. The excess molar volume values (VE) for acetonitrile mixtures are more negative than methanol mixtures. Isentropic compressibility deviation values (Δκs) in methanol mixtures are more than acetonitrile mixtures. The results have been interpreted in terms of ion−dipole interactions and structural factors of the ionic liquid and these organic solvents.
161 citations
TL;DR: Vapor−liquid equilibria, molar volumes, and volume expansion for several binary mixtures of organic solvents with carbon dioxide have been determined using a visual synthetic technique at temperatu... as mentioned in this paper.
Abstract: Vapor−liquid equilibria, molar volumes, and volume expansion for several binary mixtures of organic solvents with carbon dioxide have been determined using a visual synthetic technique at temperatu...
141 citations
TL;DR: Direct catalytic enantioselective cross aldol-type reaction of an acetate surrogate was developed using Cu alkoxide-chiral phosphine complexes as catalysts using either DTBM-SEGPHOS or a tuned BIPHEP as a chiral ligand.
141 citations
TL;DR: The variation of diffusion coefficient with temperature was found to occur in an Arrhenius-type manner for all combinations of solute and solvent, and for a given ionic liquid, the diffusional activation energies of each species were not only closely equivalent to each other, but also to the RTIL's activation energy of viscous flow.
Abstract: Measurements on the diffusion coefficient of the neutral molecule N,N,N',N'-tetramethyl-para-phenylenediamine and the radical cation and dication generated by its one- and two-electron oxidation, respectively, are reported over the range 298-348 K in both acetonitrile and four room temperature ionic liquids (RTILs). Data were collected using single and double potential step chronoamperometry at a gold disk electrode of micrometer dimension, and analysed via fitting to the appropriate analytical expression or, where necessary, to simulation. The variation of diffusion coefficient with temperature was found to occur in an Arrhenius-type manner for all combinations of solute and solvent. For a given ionic liquid, the diffusional activation energies of each species were not only closely equivalent to each other, but also to the RTIL's activation energy of viscous flow. In acetonitrile supported with 0.1 M tetrabutylammonium perchlorate, the ratio in diffusion coefficients of the radical cation and dication to the neutral molecule were calculated as 0.89 +/- 0.05 and 0.51 +/- 0.03, respectively. In contrast, amongst the ionic liquids the same ratios were determined to be on average 0.53 +/- 0.04 and 0.33 +/- 0.03. The consequences of this dissimilarity are considered in terms of the modelling of voltammetric data gathered within ionic liquid solvents.
131 citations
TL;DR: It is shown that both the anion and the cation contribute to solute retention and peak efficiency extending beyond simple "salting-out" or ion-pairing effects.
Abstract: Room temperature ionic liquids (RTIL) are molten salts starting to be used as nonmolecular solvents in separation methods mainly for their extremely low vapor pressure and thermal stability. RTILs are formed by an anion associated to a cation. This intrinsic structure gives them a dual nature. When used as additives in RPLC mobile phases to enhance basic compound separation, RTILs lose their particular physicochemical properties to become just salts. However, a given RTIL is not equivalent to another one made with the same cation. It is shown that both the anion and the cation contribute to solute retention and peak efficiency extending beyond simple “salting-out” or ion-pairing effects. Nine different alkyl-methyl-imidazolium ionic liquids with different alkyl chain length and chloride or BF4- or PF6- anions were used as additives (50 mM max. conc.) in the liquid chromatography separation of some cationic basic solutes on a Kromasil C18 column. It is shown with sodium salts and an acetonitrile−water 30/7...
124 citations
TL;DR: A new, mild, and reversible method to convert primary amides to nitriles in good yields using PdCl2 in aqueous acetonitrile is described.
114 citations
TL;DR: It is suggested that methanol be used as the preferred organic modifier with phenyl columns to achieve selectivity based upon pi-pi interactions.
109 citations
TL;DR: The simplicity of the methods presented here and the improved robustness of the resulting devices should facilitate the broader implementation of polymer microchips in microfluidic analyses.
Abstract: A new method for solvent bonding polymeric substrates to form microfluidic systems has been demonstrated. Prior to device sealing, channels in an embossed poly(methyl methacrylate) (PMMA) piece are filled with a heated liquid (paraffin wax) that forms a solid sacrificial layer at room temperature. The sacrificial material prevents the bonding solvent (acetonitrile) and softened PMMA from filling the channels. Once the sealing step is complete, the sacrificial layer is melted and removed, leaving enclosed microfluidic channels. We found that PMMA substrates welded together using this method could withstand internal pressures of >2250 psi, more than 1 order of magnitude higher than their thermally bonded counterparts. To demonstrate the usefulness of this method, microchip capillary electrophoresis (CE) devices in PMMA were created and tested. Amino acid and peptide mixtures were separated in 40 000 theoretical plates in a 2.5-cm separation distance. Electric fields as high as 1.5 kV/cm were ap...
TL;DR: The reaction equilibria involving zinc acetate and the perchlorate salts of the tetraiminodiphenol macrocycles, and the X-ray crystal structures of the complexes, have been investigated and the equilibrium constants (K) have been determined.
Abstract: The reaction equilibria [H4L]2+ + Zn(OAc)2 ⇌ [Zn(H2L)]2+ + 2HOAc (K1) and [Zn(H2L)]2+ + Zn(OAc)2 ⇌ [Zn2L]2+ + 2HOAc (K2), involving zinc acetate and the perchlorate salts of the tetraiminodiphenol macrocycles [H4L1-3](ClO4)2, the lateral (CH2)n chains of which vary between n = 2 and n = 4, have been studied by spectrophotometric and spectrofluorimetric titrations in acetonitrile. The photoluminescence behavior of the complexes [Zn2L1](ClO4)2, [Zn2L2(H2O)2](ClO4)2, [Zn2L2(μ-O2CR)](ClO4) (R = CH3, C6H5, p-CH3C6H4, p-OCH3C6H4, p-ClC6H4, p-NO2C6H4), and [Zn2L3(μ-OAc)](ClO4) have been investigated. The X-ray crystal structures of the complexes [Zn2L2(H2O)2](ClO4)2, [Zn2L3(μ-OAc)](ClO4), and [Zn2L2(μ-OBz)(OBz)(H3O)](ClO4) have been determined. The complex [Zn2L2(μ-OBz)(OBz)(H3O)](ClO4) in which the coordinated water molecule is present as the hydronium ion (H3O+) on deprotonation gives rise to the neutral dibenzoate-bridged compound [Zn2L2(μ-OBz)2]·H2O. The equilibrium constants (K) for the reaction [Zn2L2(H2O)...
TL;DR: In this article, the authors investigated linear sweep and cyclic voltammetry at platinum electrodes in the room temperature ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, ([C 4 mim][NTf 2 ]), and the conventional aprotic solvent, acetonitrile, (MeCN).
TL;DR: In this paper, the behavior of chemically or electrochemically generated ferrocenium cations has been studied in some polar organic solvents (DMF, DMSO, acetonitrile, acetone, methylene chloride) under molecular oxygen.
TL;DR: In this paper, an efficient synthesis of various substituted Hantzsch 1,4-dihydropyridines using silica gel-supported sodium bisulfate as heterogenous catalyst from an aldehyde, β-keto ester and ammonium acetate in acetonitrile is described.
TL;DR: Ab initio calculations predicted tweezer-like binding modes for receptors 1 and 2 with these anions and a higher affinity toward H 2 PO 4 - was predicted in acetonitrile.
TL;DR: In this article, the surface acidity and basicity of gamma-Ga2O3 was studied by IR spectroscopy, using pyridine, 2,6-dimethylpyridine and deuterated acetonitrile as probe molecules.
Abstract: By hydrolysis of an ethanolic gallium nitrate solution, gamma-Ga2O3 was prepared as a single-phase polymorph having a specific surface area of 160 m2 g(-1). Surface acidity and basicity of this material was studied by IR spectroscopy, using pyridine, 2,6-dimethylpyridine, acetonitrile, and carbon dioxide as spectroscopic probe molecules. For comparison, a gamma-Al2O3 sample having a surface area of 290 m2 g(-1) was also studied. On partially hydroxylated gamma-Ga2O3, the main O-H stretching bands were found at 3693 (sharp) and at 3660-3630 cm(-1) (broad), and the material proved (by adsorbed dimethylpyridine) to have a weak Bronsted acidity. Surface Lewis acidity of gamma-Ga2O3 was revealed (mainly) by adsorbed pyridine, which gave the characteristic IR absorption bands of Lewis-type adducts at 1612, 1579, 1488, and 1449 cm(-1) (values noted under an equilibrium pressure of 1 Torr at room temperature); the corresponding Lewis acid centers (coordinatively unsaturated Ga3+ ions) were found to be weaker, although more abundant, than those present on the surface of gamma-Al2O3 (unsaturated Al3+ ions). Another significant difference between gamma-Ga2O3 and gamma-Al2O3 is the smaller thermal stability of pyridine and 2,6-dimethylpyridine Lewis adducts formed on the gallium oxide. The surface basicity of gamma-Ga2O3 was studied by using carbon dioxide and deuterated acetonitrile as IR probe molecules. Adsorbed CO2 gave carbonate and hydrogen-carbonate surface species similar to those formed by gamma-Al2O3. Adsorbed acetonitrile gave rise to acetamide species, which revealed the basic character of surface O2- ions. These acetamide species were found to be more abundant on gamma-Ga2O3 than on gamma-Al2O3.
TL;DR: In this article, the effects of the bite angle on reductive elimination of dimethyl ether, acetonitrile, vinyl cyanide, and methyl ethanoate from palladium diphosphine complexes were studied by means of a density functional theory method.
TL;DR: A Ni complex of a diarylamido-based PNP ligand is an efficient and robust catalyst for coupling of acetonitrile with aldehydes.
TL;DR: In this article, the authors measured the rate coefficients for reactions of hydroxyl radical with aromatic hydrocarbons using a novel laser flash photolysis method and confirmed the rate enhancement of the addition to benzene via calculation of the transition states in the presence of explicit solvent molecules as well as a continuum dielectric field.
Abstract: The rate coefficients for reactions of hydroxyl radical with aromatic hydrocarbons were measured in acetonitrile using a novel laser flash photolysis method. Comparison of kinetic data obtained in acetonitrile with those obtained in aqueous solution demonstrates an unexpected solvent effect on the reactivity of hydroxyl radical. In particular, reactions of hydroxyl radical with benzene were faster in water than in acetonitrile, and by a significant factor of 65. Computational studies, at the B3LYP and CBS-QB3 levels, have confirmed the rate enhancement of hydroxyl radical addition to benzene via calculation of the transition states in the presence of explicit solvent molecules as well as a continuum dielectric field. The origin of the rate enhancement lies entirely in the structures of the transition states and not in the pre-reactive complexes. The calculations reveal that the hydroxyl radical moiety becomes more anionic in the transition state and, therefore, looks more like hydroxide anion. In the tran...
TL;DR: In this paper, a comparative study of the influence of porogens on the affinity and selectivity of MIP was carried out based on the computational model proposed in our previous work, and the success of the predicting model provided a experiment-free way for the selection of porogen for given template and functional monomer.
TL;DR: In this article, it was discovered that potassium permanganate is an effective heterogeneous oxidant, even without resorting to the use of a solid support, if acetonitrile is employed as the solvent.
TL;DR: The influence of lithium ion pairing on the voltammetric reduction of anthraquinone in acetonitrile is reported and potential shift measurements and Digisim modeling are shown to be in support of a complexation mechanism in which a little of the complex precipitates on the electrode surface.
Abstract: The influence of lithium ion pairing on the voltammetric reduction of anthraquinone in acetonitrile is reported. On gold electrodes, the single electron reduction generates a radical anion which forms a complex with lithium cations from the electrolyte. In situ ESR studies support this finding, and signal intensity measurements are used to estimate a value for the complexation equilibrium constant. Values calculated were of the of the order of 6000 mol(-1) dm3. Potential shift measurements and Digisim modeling are shown to be in support of a complexation mechanism in which a little of the complex precipitates on the electrode surface. The effect of lithium ion pairing is also demonstrated for the case in which 1-anthraquinonyl groups are covalently attached to multiwalled carbon nanotubes abrasively immobilized on a basal plane pyrolytic graphite electrode.
TL;DR: In this article, a simple and efficient method was developed for the synthesis of α-aminonitriles by a onepot three-component condensation of aldehydes, amines, and potassium cyanide in acetonitrile in the presence of a catalytic amount of CoCl 2 at room temperature.
Abstract: A simple and efficient method has been developed for the synthesis of α-aminonitriles by a onepot three- component condensation of aldehydes, amines, and potassium cyanide in acetonitrile in the presence of a catalytic amount of CoCl 2 at room temperature.
TL;DR: In this article, the multicomponent Strecker reaction using trimethylsilyl cyanide was accomplished without any type of Lewis acid, and the reaction performed in acetonitrile as solvent gave excellent results for any class of aldehydes, as well as amines.
TL;DR: The solvation of gallic acid (in water and acetonitrile) is studied by means of its spectroscopic properties and various solvation models obtained in terms of both purely classical and density functional approaches are tested.
Abstract: The solvation of gallic acid (in water and acetonitrile) is studied by means of its spectroscopic properties. IR, UV, and NMR spectra are predicted by using various solvation models obtained in terms of both purely classical and density functional approaches. Comparison with experiments is used to validate solvation models. Hydrogen-bond and long-range (or bulk) effects are evaluated by comparing different solvation models. A continuum-only approach, a purely discrete, and a mixed continuum/discrete approach based on quantum-mechanical and classical molecular-dynamics solute−solvent clusters are tested.
TL;DR: In this article, it has been shown that the rate of hydrogen peroxide consumption in an alkane oxidation by the O2-H2O2-nBu4NVO3-pyrazine-2-carboxylic acid reagent in acetonitrile is noticeably lower in the presence of an acid than in its absence.
Abstract: It has been found that the rate of hydrogen peroxide consumption in an alkane oxidation by the “O2–H2O2–nBu4NVO3–pyrazine-2-carboxylic acid” reagent in acetonitrile is noticeably lower in the presence of an alkane than in its absence. This paradoxical phenomenon at the first glance can be explained if we assume that acetonitrile used as a solvent is efficiently oxidized by the system in the absence of alkane. This oxidation is depressed by alkane additive due to the competition between the alkane and acetonitrile for the active hydroxyl radicals efficiently generated by the reagent. It has been also shown that the H2O2 decomposition in the presence of an alkane occurs as a radical non-chain process.
TL;DR: The resulting conducting polymer sensor offers interesting analytical performances such as: fast and linear responses towards the neurotransmitters dopamine and l-dopa towards the neuroleptic chlorpromazine with low detection limits, and simultaneous detection and well-resolved signals between the compounds of interest and ascorbic acid.
TL;DR: Vanadyl triflate is found to catalyze trimethylsilyl cyanide addition to a variety of ketones and aldehydes in acetonitrile at room temperature under very mild and convenient conditions to afford the corresponding cyanohydrins in a short reaction period (1-7h) as mentioned in this paper.
Abstract: Vanadyl triflate is found to catalyze trimethylsilyl cyanide addition to a variety of ketones and aldehydes in acetonitrile at room temperature under very mild and convenient conditions to afford the corresponding cyanohydrins in excellent yields (79–96%) in a short reaction period (1–7 h). The high yields of products, compatibility of the other functional groups, and reusability of catalyst is the advantages of this method.
TL;DR: In this paper, a simple and effective method for the generation and study of radical cations of aromatic amines has been described, based on the donation of an electron from the amines to Cu 2+.