Showing papers on "Acetonitrile published in 1993"
TL;DR: In this paper, the coulombic capacity and reversibility of rechargeable magnesium batteries were investigated in acetonitrile solutions containing,,, and, and they reached up to 170 Ah/kg.
Abstract: The electrochemistry of , , , , and has been studied in several organic solvents containing in view of their application as positive electrodes in rechargeable magnesium batteries. Only showed promising coulombic capacity and reversibility. Mg2+ insertion into this oxide depends on the ratio between the amounts of and Mg2+ as well as on the absolute amount of in the electrolyte. Water molecules preferentially solvating Mg2+ions appear to facilitate the insertion process. The highest coulombic capacities of up to 170 Ah/kg were reached in acetonitrile solutions containing .
213 citations
TL;DR: In this article, the OD and CN stretching vibrations of HDO and CD 3 CN molecules have been used as probes of the structural environments of water and acetonitrile in infrared spectroscopy.
Abstract: Mixtures of water and acetonitrile in the full concentration range have been studied by infrared spectroscopy. OD and CN stretching vibrations of HDO and CD 3 CN molecules have been used as probes of the structural environments. Acetonitrile molecules which are unaffected by water molecules are found for a broad concentration range (0.1≤xH 2 O≤0.8), showing that a preferential solvation occurs. The strong tendency for self-association of water molecules is evident from the occurrence of a broad OD stretching band. Chains of water molecules linked by hydrogen bonds are suggested to be formed rather than spherical clusters
159 citations
TL;DR: The solvent-induced frequency shifts (SIFS) for the C≡N stretching vibration (ν 2 ) in acetitrile and deuterated acetonitrile have been determined in a wide variety of organic solvents.
Abstract: The solvent-induced frequency shifts (SIFS) for the C≡N stretching vibration (ν 2 ) in acetonitrile and deuterated acetonitrile have been determined in a wide variety of organic solvents. It is shown that this band is shifted to higher energies in the presence of solvents which are more stronger Lewis acids than acetonitrile itself. On the other hand, in the presence of solvents which are stronger Lewis bases, the ν 2 band is shifted to lower energies. This is taken to be evidence that the electronegative end of the Lewis base interacts with the methyl group in acetonitrile. Supporting evidence for this conclusion is reported on the basis of shifts in the symmetrical (ν 1 ) and antisymmetrical (ν 5 ) CD3 stretching bands
128 citations
TL;DR: In this paper, a three-step cycle at pH 7, 40 o C (cyclen=1,4,7,11-tetraazacyclododecane) is described, which involves equilibrium coordination of acetonitrile to 1 (K 1 =2.5 M -1 ) followed by intramolecular metal hydroxide attack on the coordinated nitrile resulting in formation of the chelated acetamide (k 2 =4.7×10 -3 s -1 ), and dissociation of the amide (k 3 =
Abstract: [Co(cyclen)(OH 2 ) 2 ] 3+ (1) efficiently catalyzes hydration of acetonitrile to acetamide in a three-step cycle at pH 7, 40 o C (cyclen=1,4,7,11-tetraazacyclododecane). The mechanism involves (a) equilibrium coordination of acetonitrile to 1 (K 1 =2.5 M -1 ) followed by (b) intramolecular metal hydroxide attack on the coordinated nitrile resulting in formation of the chelated acetamide (k 2 =4.7×10 -3 s -1 ) and (c) dissociation of the chelated amide (k 3 =3.3×10 -4 s -1 )
124 citations
TL;DR: In this article, a reagent called Hexamethyldisilazane (HMDS) in presence of a catalytic amount of anhydrous zinc chloride silylates efficiently and selectively different types of alcohols and phenols.
90 citations
TL;DR: In this article, the quenching rate constants k q by molecular oxygen 3 O 2 (3 Σ g - ) were measured for anthracenecarbonitriles (AC) in acetonitrile and benzene.
Abstract: Fluorescence quenching rate constants k q by molecular oxygen 3 O 2 ( 3 Σ g - ) were measured anthracenecarbonitriles (AC) in acetonitrile and benzene and for five acridinium ions in acetonitrile. The k q 's for acridinium ions decrease with an increase in the free enthalpy change ΔG of full electron transfer from the first excited singlet fluorescer 1 M * to 3 O 2 in acetonitrile and become smaller than one-hundredth of the diffusion-controlled limit, k diff
87 citations
TL;DR: In this article, the quenching of 1-naphthol fluorescence by carbon tetrachloride (CCl 4 ) has been studied in different solvent mixtures of acetonitrile and dioxane at room temperature.
Abstract: The quenching of 1-naphthol fluorescence by carbon tetrachloride (CCl 4 ) has been studied in different solvent mixtures of acetonitrile and dioxane at room temperature. The quenching is found to be appreciable and a positive deviation from linearity was observed in the Stern-Volmer plot in all the solvent mixtures even at moderate CCl 4 concentrations (0.1 M or less). This could be explained satisfactorily by a static-dynamic model. The static quenching constant K o values indicate that the ground-state complex is weak and independent of solvent polarity, whereas the dynamic quenching constant K sv depends on the solvent polarity.
81 citations
TL;DR: In this paper, the effect of solvent on the difference in energy between the E and Z rotamers of methyl formate and methyl acetate has been studied using reaction field theory and the spherical cavity approximation.
Abstract: The effect of solvent on the difference in energy between the E and Z rotamers of methyl formate and methyl acetate has been studied using reaction field theory and the spherical cavity approximation. The calculated free energy difference for methyl formate was reduced from 5.2 kcal/mol for e=35.9 (acetonitrile). Similarly, with methyl acetate the difference was reduced from 8.5 to 5.2 kcal/mol. The changes in geometry, dipole moments, charge distributions, and vibrational frequencies on going from e=1 to 35.9 also were calculated and are in accord with increasing polar character of the carbonyl group in the more polar solvent
79 citations
TL;DR: In this article, the authors used acetonitrile deproteinization to remove serum proteins for the analysis of drugs and small molecules by capillary electrophoresis and found that the results showed that 60% of the deproteinized serum proteins exhibited higher plate numbers and peak heights.
78 citations
TL;DR: In this article, the quantum yield of trans-stilbene and 4a,4b-dihydrophenanthrene was measured in cyclohexane, hexane, acetonitrile, and methanol solvents.
Abstract: Photochemical quantum yields for the formation of Trans-stilbene and 4a,4b-dihydrophenanthrene from cis-stilbene have been measured in cyclohexane, hexane, acetonitrile, and methanol solvents. Degassed cis-stilbene samples at 27 o C were irradiated at 280 nm, and the formation of photoproducts was monitored by absorption spectroscopy. The quantum yield for formation of dihydrophenanthrene is two to three times greater in the nonpolar solvents than in the polar ones (15-19% vs 5-8%), while a slight solvent dependence of the yield of trans-stilbene is observed (35-39%in the polar solvents vs 32-35% in the hydrocarbons)
76 citations
TL;DR: In this paper, the reaction of mercuric acetate with closo-1,2-Li2-1,2-C2BloHloHg yielded (9)mercuracarborand-3, (C2BLoHlHg), (l), in 60% yield.
Abstract: The reaction of mercuric acetate with closo-1 ,2-Li2-1 ,2-C2BloHlo yielded (9)mercuracarborand-3, (C2BloHloHg), (l), in 60% yield. Compound 1 was characterized by multinuclear NMR spectroscopy and its chloride ion complex, l.CI-, by negative ion FAB mass spectroscopy. The structure of 1 was determined by X-ray crystallography. 1 crystallized from acetonitrile in the monoclinic space group P21/c with a = 13.358 (2), b = 26.846 (4), and c = 20.375 A, 0 = 109.694 (S)", V = 7909 AS, and 2 = 4. Data were collected on a Picker FACS-1 diffractometer, using Mo Ka radiation, to a maximum 20 = 45", giving 10 348 unique reflections, and the structure was solved by heavy atom methods. The final discrepancy index was R = 0.044, R, = 0.049 for 5193 independent reflections with I > 34). The chloride ion complex of 1, IClLi, was formed upon treatment of 1 with LiCI. The complexation behavior of 1 in acetone was studied by 199Hg NMR spectroscopy.
TL;DR: In this paper, the X-ray absorption edge and EXAFS spectra of the acetonitrile, dimethyl sulfoxide, pyridine and tetrahydrothiophene solvated copper(I) ions have been measured in solution.
Abstract: X-ray absorption edge and EXAFS spectra of the acetonitrile, dimethyl sulfoxide, pyridine and tetrahydrothiophene solvated copper(I) ions and the acetonitrile and dimethyl sulfoxide solvated copper(II) ions have been measured in solution. Analysis reveals that the copper(I) solvates are most probably tetrahedral, and the following Cu-solvate bond distances have been found: Cu-N = 1.99(2) [angstrom] in acetonitrile, Cu-O = 2.09(4) [angstrom] in dimethyl sulfoxide, Cu-N = 2.06(1) [angstrom] in pyridine, and Cu-S = 2.30(1) [angstrom] in tetrahydrothiophene. The copper(II) solvates are most probably Jahn-Teller distorted octahedrons, and the following equatorial Cu-solvate bond distances have been found: Cu-N = 1.99(1) [angstrom] in acetonitrile, and Cu-O = 1.98(1) [angstrom] in dimethyl sulfoxide. An 1.0 M solution of copper(II) trifluoromethanesulfonate in acetonitrile has been studied by means of the large-angle X-ray scattering technique, and the following Cu-N and Cu-C distances have been found for the Cu(CH[sub 3]CN)[sub 4][sup 2][sup +] complex: 1.99(1) and 3.12(1) [angstrom], respectively. No solvate molecules in the axial positions could however be seen by any of the technique used. The structure of the tetraaquacopper(I) ion has been assumed to be tetrahedral, and from a correlation between the difference in bond length between the copper(I) and copper(II) solvates and the disproportionationmore » constants of copper(I) in the solvent, the Cu-O bond distance is predicted to be approximately 0.14 [angstrom] longer than the equatorial Cu-O distances in the Jahn-Teller distorted hexaaquacopper(II) complex, thus about 2.13 [angstrom].« less
TL;DR: In this paper, a method for the determination of cyanide in blood using head-space capillary gas chromatography (HS-GC) with nitrogen-phosphorus detection (NPD) was developed.
TL;DR: The degree of uncertainty in ΔG hydride (R + ) s depends primarily upon the errors associated with the determination of the reversible electrode potentials for the (R. /R - ) and (R+ /R. ) couples as discussed by the authors.
Abstract: Hydride affinities of organic cations in solution, defined as the free energy change for the reaction (R + ) s +(H - ) s ⇄(RH) s , where the subscript s refers to the solvent, can be determined using either of two equations (eqs 5 and 7) derived from thermochemical cycles. The degree of uncertainty in ΔG hydride (R + ) s depends Primarily upon the errors associated with the determination of the reversible electrode potentials for the (R . /R - ) and (R + /R . ) couples
TL;DR: In this article, the surface pressure-molecular area isotherms of Langmuir-Blodgett C[sub 60] and Eicosanoic acid (arachidic acid) mixed films were measured at the air-water interface, and the electrochemical behavior of the LBL films on a hydrophobic gold electrode in acetonitrile solutions was described.
Abstract: Surface pressure-molecular area isotherms of Langmuir films of pure C[sub 60] and C[sub 60]-eicosanoic acid (arachidic acid) mixed films were measured at the air-water interface, and the electrochemical behavior of the Langmuir-Blodgett films on a hydrophobic gold electrode in acetonitrile solutions is described. The formation of highly incompressible monolayer and multilayer films at the air-water interface was reconfirmed and was strongly dependent on the experimental conditions, such as the purity of the fullerene, spreading solvent, and the age and history of the spreading solution. The voltammetric response of Langmuir-Blodgett C[sub 60] films indicates a higher solubility of the reduced species than that observed for thicker films prepared by drop coating. 22 refs., 6 figs.
TL;DR: In this paper, an X-ray structure determination of 1,1′-Bis(diphenylphosphino)ferrocene (dppf) reacts with [Pd(CH 3 CN) 4 ](BF 4 ) 2 to give a stable 1/1 complex in which there is a bonding interaction between Fe and Pd atoms.
TL;DR: In this article, conductance data for lithium bis(trifluoromethanesulfone)imide, LiN(CF3SO2)2, and LiAsF6 were reported for the solvents water, propylene carbonate, acetonitrile and methyl formate at 25°C.
Abstract: Conductance data for lithium bis(trifluoromethanesulfone)imide, LiN(CF3SO2)2, are reported for the solvents water, propylene carbonate, acetonitrile and methyl formate at 25°C. Limiting molar conductivitiesA0, association constants KA, and triple ion formation constants Kt are reported where applicable. These data are compared with literature data for the commonly studied lithium salts LiClO4 and LiAsF6. Non-coulombic energy contributions to ion pair formation are evaluated and discussed in terms of ion-ion and ion-solvent interactions.
TL;DR: The chemical modifications and immobilization of cytochrome c were able to change its biocatalytic activity and stability in the organic solvent system, and the best catalytic efficiency was obtained in a system containing 50% tetrahydrofuran in phosphate buffer.
TL;DR: Using the inversion/recovery method, deuterium longitudinal relaxation times were measured for binary solutions of methanol and D 2 O and acetonitrile, and for these mixtures in contact with two different reversed-phase liquid chromatographic stationary phases as discussed by the authors.
Abstract: Using the inversion/recovery method, deuterium ( 2 H) longitudinal relaxation times, (T 1 ), of deuterium oxide were measured for binary solutions of methanol and D 2 O and acetonitrile and D 2 O and for these mixtures in contact with two different reversed-phase liquid chromatographic stationary phases. Changes in the D 2 O T 1 for the solutions in contact with the stationary phase compared to those observed for the solutions alone give a qualitative understanding of the degree of association of water with the stationary phase
TL;DR: In this paper, a Fourier transform infrared spectroscopy (FTIR) was used to study the oxidation properties of LiAsF{sub 6}/acetonitrile and LiClO{sub 4}/ACetonitriles solutions containing 0.003-0.05M H{sub 2}O.
Abstract: The oxidation of LiAsF{sub 6}/acetonitrile and LiClO{sub 4}/acetonitrile solutions containing 0.003--0.05M H{sub 2}O was studied on platinum and glassy carbon electrodes by in situ Fourier transform infrared spectroscopy. Both the solvent and the solute are unstable at potentials positive to ca. 2.2 V vs. SCE. The main oxidation product is CO{sub 2}. Other products detected are: via a reaction of acetonitrile with trace water as substantiated by the occurrence of an isotopic shift of the CO{sub 2} stretching vibration when using H{sub 2}{sup 18}O. The rate of the CO{sub 2} formation is increased by the presence of perchlorate anions and the Pt surface.
TL;DR: In this paper, the authors explored the nature of cation-anion interactions in the solid tetraethylammonium salts of the monoanions of p-tert-butylcalix[4]arene (L2) and its dihomooxa analogue (L3) with room temperature single-crystal X-ray studies.
Abstract: Syntheses of a number of tetraalkylammonium derivatives of various calix[n]arenes (n= 4, 6, 8) have been conducted by reacting the tetraalkylammonium hydroxides with the parent calixarenes. 1 H NMR studies in acetone and dimethylsulfoxide (DMSO) solvents have shown that cation inclusion by the anionic calixarenes occurs in some cases for only the tetramethyl- and tetraethyl-ammonium cations, indicating that different forms of ion association must occur in solution. The nature of cation–anion interactions in the solid tetraethylammonium salts of the monoanions of p-tert-butylcalix[4]arene (L2) and its dihomooxa analogue (L3) has been explored by room temperature single-crystal X-ray studies of the two salts and the parent ligand L3, all recrystallised variously solvated from acetonitrile. In both solid salts, columnar arrays of alternating cations and anions are found: in the dihomooxa ligand (L3) salt, the cations are captured within the ligand cup, forming contact ion pairs, the column comprising stacks of these. By contrast, the columnar array found in the parent ligand (L2) salt consists of discrete moieties, with the anion cavity occupied by acetonitrile. The free (neutral) ligand L3, as its acetonitrile monosolvate, contains the acetonitrile within the ligand cavity also. The structure determination of the unsubstituted calix[4]arene ligand, L1, is recorded as its ⅓ acetonitrile solvate, with location of all phenolic hydrogen atoms bridging their associated oxygen atoms; the acetonitrile in this case simply occupies a lattice void, as in the isomorphous acetone solvate.
TL;DR: In this paper, an indirect electroreduction of N-allylic and N-propargyl-α-bromo amides and o bromoacryloylanilides gave the corresponding 5-membered lactams.
Abstract: Nickel(II) complex-catalysed indirect electroreduction of N-allylic and N-propargyl-α-bromo amides and o-bromoacryloylanilides gave the corresponding 5-membered lactams. The product distribution was affected by the ability of the solvent to donate hydrogen atom. The electroreduction of N-allyl-N(bromoacetyl)toluene-p-sulfonamide 1a in DMF and acetonitrile yielded as main product the 4-methylpyrrolidinone 2a(41%) and the 4-(bromomethyl)pyrrolidinone 3a(33%), respectively. On addition of 2 mol equiv. of a hydrogen-atom donor (Ph2PH) to the reaction of bromo amide 1a in acetonitrile, compound 1a provided compound 2a(58%) as the sole cyclised product.
TL;DR: In this paper, a model for solvation of the activated complex based on three contiguous spheres corresponding to the two phenyl rings and the carbonyl group is described and used to assess the outer-sphere contribution to the Gibbs activation energy for electron transfer.
Abstract: The kinetics of electroreduction of benzophenone have been studied at a mercury ultramicroelectrode in seven aprotic solvents. In addition, the temperature dependence of the standard rate constant was determined in three solvents, and the effect of tetraalkylammonium cations on the kinetic parameters was assessed in acetonitrile. On the basis of an analysis of the solvent effects, it is shown that this fast electron-transfer reaction is adiabatic. A model for solvation of the activated complex based on three contiguous spheres corresponding to the two phenyl rings and the carbonyl group is described and used to assess the outer-sphere contribution to the Gibbs activation energy for electron transfer
TL;DR: A detailed study of the effect of alkali-metal perchlorates on the spectral features of acetonitrile has been made using attenuated total reflection FTIR spectroscopy.
Abstract: A detailed study of the effect of alkali-metal perchlorates, especially LiClO4 and NaClO4, on the spectral features of acetonitrile has been made using attenuated total reflection FTIR spectroscopy. The effect of the electrolyte on the C—H stretching and deformation modes together with new information on the CN and C—C stretching modes is analysed in detail. It is shown on the basis of spectra obtained in the deuteriated acetonitrile that the Cl—O symmetrical stretching vibration (ν1) is IR active when the anion is paired to a cation. Analysis of the perchlorate region of the spectrum provided further information on ion pairing in this system.
TL;DR: In this paper, the cyclic voltammetry of [(CN)2RuIIPc]2− in acetonitrile or dichloromethane showed two oxidation couples at E 1 2 = 0.31 and 0.85 V (vs S.C.E.).
TL;DR: The primary chemical equilibria which define autoprotolysis in aqueous binary solvents have been elucidated and the constants of these equilibrium values were computed in this paper.
Abstract: The primary chemical equilibria which define autoprotolysis in aqueous binary solvents have been elucidated and the constants of these equilibria computed for aqueous solvent mixtures of methanol, ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2,3-propanetriol, acetonitrile, acetone, tetrahydrofuran, dimethyl sulfoxide, 1,4-dioxane, and formic acid. The values of these constants explain the different behaviors of the diverse binary solvents. From these fundamental constants, the plan value at any solvent composition of any of the binary solvents studied can be accurately computed
TL;DR: In this paper, the infrared-visible sum-frequency generation (SFG) was employed in an internal reflection geometry to investigate, in situ, the adsorption of acetonitrile on ZrO2 from liquid and vapor.
Abstract: Infrared‐visible sum‐frequency generation (SFG) is employed in an internal reflection geometry to investigate, in situ, the adsorption of acetonitrile on ZrO2 from liquid and vapor. This configuration induces large field enhancements near the critical angle that increase signal levels by more than 100‐fold compared with reflection from the liquid or vapor side of the interface. Acetonitrile is a widely used, highly polar, chromatographic solvent that has simple structure and strong stretching modes with large frequency separation, making it an ideal liquid for SFG studies. The C≡N and C–H stretching modes are observed at submonolayer and neat liquid coverages on ZrO2. The relative polarization dependent SFG oscillator strengths are determined providing estimates of the binding energy, 4.7±0.2 kcal/mol, and the mean orientation of the molecular axis to the surface, 22±2°. Spectra of CD3CN show resolvable structure in the C≡N and C–D stretching regions, suggesting the presence of aggregates on the surface. ...
TL;DR: A series of molecular dynamics simulations have been performed on tert-butylcalix[4]arene tetramide ligand L and its complexes with cations Li + to Cs + and Eu 3+ in acetonitrile solution in order to elucidate the structural basis of complexation of cations by an ionophore possessing a highly flexible nonpreorganized pseudocavity.
Abstract: A series of molecular dynamics (MD) simulations have been performed on tert-butylcalix[4]arene tetramide ligand L and its complexes with cations Li + to Cs + and Eu 3+ in acetonitrile solution in order to elucidate the structural basis of complexation of cations by an ionophore possessing a highly flexible nonpreorganized pseudocavity. Comparison of its dynamic behavior in acetonitrile and in water demonstrates the dramatic solvent effect on the extent of ligand wrapping around the complexed ions. The binding mode of cation complexes in acetonitrile differs significantly from the picture provided by the solid-state structure of LK + complex and from structures simulated in gas phase and in water