Showing papers on "Acetonitrile published in 1998"
TL;DR: In this paper, the crystal structure of compound 1 revealed that linear [Ag(Et2-Bimy)2]+ and [AgBr2]- groups were associated through a short AgI−AgI contact (2.956 A).
1,033 citations
TL;DR: In this paper, the structure of acetonitrile−water mixtures has been investigated by X-ray diffraction with an imaging plate detector and IR spectroscopy over a wide range of acetitrile mole fractions.
Abstract: The structure of acetonitrile−water mixtures has been investigated by X-ray diffraction with an imaging plate detector and IR spectroscopy over a wide range of acetonitrile mole fractions (0.0 ≤ XAN ≤ 1.0). Reichardt ETN and Sone-Fukuda DII,I values were also measured for the mixtures. It has been found from the X-ray data that in pure acetonitrile an acetonitrile molecule interacts with two nearest neighbors by antiparallel dipole−dipole interaction together with a small shift of the two molecular centers and that two acetonitrile molecules in the second-neighbor shell interact with a central molecule through parallel dipole−dipole interaction. Thus, acetonitrile molecules are alternately aligned to form a zigzag cluster. On addition of water into pure acetonitrile, water molecules interact with acetonitrile molecules through a dipole−dipole interaction in an antiparallel orientation. The IR spectra of O−D and C⋮N stretching vibrations, observed for mixtures of acetonitrile AN and water containing 20% D2...
256 citations
TL;DR: Several cobalt porphyrins (CoP) have been reduced by radiation chemical, photochemical, and electrochemical methods, in aqueous and organic solvents.
Abstract: Several cobalt porphyrins (CoP) have been reduced by radiation chemical, photochemical, and electrochemical methods, in aqueous and organic solvents. In aqueous solutions, the CoIP state is stable at high pH but is shorter lived in neutral and acidic solutions. Stable CoIP is also observed in organic solvents and is unreactive toward CO2. One-electron reduction of CoIP leads to formation of a species that is observed as a transient intermediate by pulse radiolysis in aqueous solutions and as a stable product following reduction by Na in tetrahydrofuran solutions. The spectrum of this species is not the characteristic spectrum of a metalloporphyrin π-radical anion and is ascribed to Co0P. This species binds and reduces CO2. Catalytic formation of CO and HCO2- is confirmed by photochemical experiments in acetonitrile solutions containing triethylamine as a reductive quencher. Catalytic reduction of CO2 is also confirmed by cyclic voltammetry in acetonitrile and butyronitrile solutions and is shown to occur ...
211 citations
Journal Article•
TL;DR: Several cobalt porphyrins (CoP) have been reduced by radiation chemical, photochemical, and electrochemical methods, in aqueous and organic solvents as discussed by the authors.
Abstract: Several cobalt porphyrins (CoP) have been reduced by radiation chemical, photochemical, and electrochemical methods, in aqueous and organic solvents. In aqueous solutions, the CoIP state is stable at high pH but is shorter lived in neutral and acidic solutions. Stable CoIP is also observed in organic solvents and is unreactive toward CO2. One-electron reduction of CoIP leads to formation of a species that is observed as a transient intermediate by pulse radiolysis in aqueous solutions and as a stable product following reduction by Na in tetrahydrofuran solutions. The spectrum of this species is not the characteristic spectrum of a metalloporphyrin π-radical anion and is ascribed to Co0P. This species binds and reduces CO2. Catalytic formation of CO and HCO2- is confirmed by photochemical experiments in acetonitrile solutions containing triethylamine as a reductive quencher. Catalytic reduction of CO2 is also confirmed by cyclic voltammetry in acetonitrile and butyronitrile solutions and is shown to occur ...
167 citations
TL;DR: In this paper, anhydrous Chloramine-T was added to an acetonitrile solution of alkenes in the presence of various CuCl catalysts and MS-5A, and the corresponding aziridines were obtained in moderate to good yields.
110 citations
TL;DR: In this paper, the synthesis of homopolymers, copolymers and composites of aniline and pyrrole in nitrogen atmosphere using various solvent and supporting electrolytes was investigated.
93 citations
TL;DR: Ammoxidation of ethane to acetonitrile was studied over a variety of metal ion exchanged zeolite catalysts in this article, and it was shown that Co 2+ is the most active metal for acetitrile formation.
89 citations
TL;DR: In this paper, the tetraalkylated derivatives of 2,8,14,20-tetrathiacalix[4]arenes were synthesized by refluxing of the derivatives in acetone or acetonitrile with the alkylation agent (R-I, R-Br).
77 citations
TL;DR: Interactions between metal ions and added organic ligands became more selective with increasing pH, showing the expected preference of hard and soft ligands for metal ions of the corresponding type.
Abstract: The distribution of metal species in solution was determined using flow injection electrospray ionization mass spectrometry. Complexes formed by selected metal ions with added organic ligands in 50:50 water/acetonitrile and 50:50 water/methanol under acidic, neutral, and basic conditions were detected using electrospray ionization conditions optimized to best represent solution-phase interactions. Metal species containing acetate, nitrate, and solvent molecules predominated in acidic solution but became less abundant at higher pH. Interactions between metal ions and added organic ligands became more selective with increasing pH, showing the expected preference of hard and soft ligands for metal ions of the corresponding type. Species distributions also tended toward larger complexes as pH increased. Overall ion yield was greater for aqueous acetonitrile than for aqueous methanol solutions; however, reduction of copper(II) in aqueous acetonitrile resulted in the detection of copper(I) complexes for certain...
76 citations
TL;DR: Several aldehydes have been converted to the corresponding acids in good to excellent yields as discussed by the authors, and the oxidant was Oxone® (potassium peroxymonosulfate).
73 citations
TL;DR: In this paper, the structure of the films is discussed in terms of covalent bonding between the fullerenes and the metal atoms or complexes within the film and the films have been examined by scanning electron microscopy, which shows variations in the nature of the three morphologies with the film formed from (PhCN)2PdCl2 displaying the greatest uniformity and smoothest surface.
Abstract: Electrochemical reduction of C60 in 4:1 toluene/acetonitrile solution in the presence of (PhCN) 2- PdCl2, Ir(CO)2Cl(p-toluidine), or (CF3CO2)4Rh2 produces three different, redox-active, black films that coat the electrode. These films are insoluble in common organic solvents and adhere strongly to the electrode surface. Film formation has been monitored by multiscan cyclic voltammetry, which gives information about the requirements for film growth. The three different films (on the original electrodes) can be transferred to a solution of acetonitrile that contains only the supporting electrolyte, tetra( n-butyl)ammonium perchlorate, where the films retain their redox activity. Each film displays a significant decrease in resistivity ( i.e. a window of conductivity) in the potential region in which it is grown and in which it displays redox activity. The films have been examined by scanning electron microscopy, which shows variations in the nature of the three films' morphologies with the film formed from (PhCN)2PdCl2 displaying the greatest uniformity and smoothest surface. Analysis of the films by infrared spectroscopy and laser desorption mass spectrometry reveals that intact C 60 units are present within each film. Treatment of the palladium/C60 film with triphenylphosphine results in film dissolution and the formation of the previously characterized complex, ( 2 -C60)Pd(PPh3)2. The rhodium/ C60 film dissolves in pyridine and 19 F{ 1 H} NMR spectroscopy reveals that (CF3CO2)4Rh2 is extracted intact from the film. The structure of the films is discussed in terms of covalent bonding between the fullerenes and the metal atoms or complexes within the film.
TL;DR: In this paper, a deep desulfurization process of light oil, effected by a combination of photochemical reaction and organic two-phase liquid−liquid extraction, has been investigated, which is comprised of two stages.
Abstract: A novel deep desulfurization process of light oil, effected by a combination of photochemical reaction and organic two-phase liquid−liquid extraction, has been investigated. The process is comprised of two stages. The first consists of the transfer of the sulfur-containing compounds from the light oil to an aqueous-soluble polar solvent. This is then followed by the photooxidation and photodecomposition of the sulfur-containing compounds in the solvent by UV irradiation, using a high-pressure mercury lamp. The operations are carried out under conditions of room temperature and atmospheric pressure. Acetonitrile was found to be the most suitable polar solvent for the process. In acetonitrile, dibenzothiophene (DBT) is converted to DBT 5-monoxide and then to DBT 5,5-dioxide, dibenz[c,e][1,2]oxathiin 6-oxide, and aromatic sulfonate or sulfinate anion by the UV irradiation. These products are highly polarized and are therefore not distributed into the nonpolar light oil phase. An adverse effect of naphthalene...
TL;DR: In this article, a dendrimer with a fluorescent core consisting of a rubicene moiety is synthesized and the hydrodynamical volume is determined in toluene, a good solvent, acetone, a medium quality solvent, and acetonitrile, a poor solvent.
Abstract: Four generations of a dendrimer with a fluorescent core consisting of a rubicene moiety are synthesized. The biexponential nature of fluorescence decay in toluene indicates the presence of two emitting conformations. Molecular modeling suggests that a conformation where the dendrons interact with the core is not improbable. The relative weight of the two decay times indicates that the contribution of that conformation in toluene increases as the dendrimer generation increases. In acetone and acetonitrile however the fluorescence decay is, except for the fourth generation, monoexponential. The hydrodynamical volume of the dendrimer is determined in toluene, a good solvent, acetone, a medium quality solvent, and acetonitrile, a poor solvent, with the time-resolved fluorescence depolarization technique. No change of the hydrodynamical volume is found in toluene in a temperature range between 20 and 94 °C. This suggests that the dendrimers of all the generations are fully expanded in this solvent. In acetonit...
TL;DR: In this article, the reactions of four (E)-β-alkylvinyl(phenyl)iodonium salts with chloride ion were examined in acetonitrile and in several other solvents at 25 °C.
Abstract: The reactions of four (E)-β-alkylvinyl(phenyl)iodonium salts with chloride ion were examined in acetonitrile and in several other solvents at 25 °C. The β-methyl-, β-octyl-, and β-isopropyl-substit...
TL;DR: In this article, the authors used laser flash photolysis with time-resolved infrared detection of transients (LFP-TRIR) to study the IR spectroscopy and reactivity of a number of substituted ketenes.
Abstract: Laser flash photolysis with time-resolved infrared detection of transients (LFP-TRIR) has been used to study the IR spectroscopy and reactivity of a number of substituted ketenes, prepared by the 308-nm photolysis of α-diazocarbonyl precursors in acetonitrile solution at room temperature. The correlation of the experimental ketene asymmetric stretching frequency to the Swain−Lupton field (F) and resonance (R) effect substituent parameters was unsatisfactory, whereas the correlation to the inductive substituent parameter (σI) of Charton gave excellent results. This suggests that the asymmetric stretching frequency of substituted ketenes depends mainly on the inductive (i.e., field) effect of the substituents. The mechanism and kinetics of the reactions of these ketenes with various amines in acetonitrile were also studied. An intermediate species identified as either zwitterionic ylide or amide enol formed in the nucleophilic addition of the secondary amine to the Cα of the ketene is observed by TRIR. The ...
TL;DR: In this article, the use of tricyclic strong nonionic Lewis bases P(MeNCH2CH2)3N and P(HNCH 2CH2)(i-Pr NCH2 CH2)2N for the direct catalytic synthesis of a variety of functionalized α,β-unsaturated nitriles in high yields from aldehydes and acetonitrile or benzyl cyanide at 40−50 °C.
Abstract: We report herein the use of 3−30 mol % of a new class of tricyclic strong nonionic Lewis bases P(MeNCH2CH2)3N and P(HNCH2CH2)(i-PrNCH2CH2)2N for the direct catalytic synthesis of a variety of functionalized α,β-unsaturated nitriles in high yields from aldehydes and acetonitrile or benzyl cyanide at 40−50 °C. Evidence for a novel mechanistic pathway proposed for this reaction in a polar protic solvent such as methanol, and a nonpolar aprotic solvent such as benzene is also presented. Under these conditions, primary and secondary aliphatic aldehydes do not condense satisfactorily with acetonitrile to give the α,β-unsaturated nitrile, and ketones do not condense with either benzyl cyanide or acetonitrile.
TL;DR: The insoluble materials responsible for the commonly encountered electrode fouling during ferrocene oxidation in incompletely degassed solutions, are a mixture of hydrous iron(III) oxide and the organic polymer poly(cyclopentane-1,3-dione-4,5-diyl).
TL;DR: In this paper, cyclic voltammetry, electrochemical quartz crystal microbalance, X-ray i raction, and UV-visible spectroscopy were used to characterize amorphous Fe 2 O 3 films.
Abstract: Electrodeposition of amorphous Fe 2 O 3 films of nanometer size was performed by reduction of Fe(ClO 4 ) 3 or Fe(ClO 4 ) in oxygenate acetonitrile. Cyclic voltammetry has shown that the oxide-film formation occurs via oxidation of electrodeposited metal by dissolved oxygen. The oxide films were characterized by cyclic voltammetry, electrochemical quartz crystal microbalance, X-ray i raction, and UV-visible spectroscopy. The films are reversibly reduced in acetonitrile + LiCIO, in two redox processes to the Fe 3 O 4 and FeO oxides via lithium intercalation. The UV-visible (UV-vis) spectrum displays absorption with an optical gap (1.75 eV) characteristic of amorphous Fe0 3 . Spectroelectrochemistry has shown that reduction causes bleaching of the yellowish films (electrochromic efficiency ≅30 C -1 cm 2 at 400 nm). Heating the films at 500 °C converts them to the crystalline α-Fe 2 O 3 form with loss of electroactivity.
TL;DR: In this paper, NMR chemical shift measurements of the hydroxyl proton in methanol were made as a function of concentration in six solvents: carbon tetrachloride, benzene, chloroform, acetonitrile, acetone and dimethyl sulphoxide.
Abstract: Proton NMR chemical shift measurements of the hydroxyl proton in methanol were made as a function of concentration in six solvents: carbon tetrachloride, benzene, chloroform, acetonitrile, acetone and dimethyl sulphoxide. The hydroxyl proton peak shifts by approximately 5 ppm in carbon tetrachloride and benzene, and by lesser amounts in the other solvents. This behaviour is due to hydrogen bonding interactions of the methanol with other methanol molecules or with the solvent, and is correlated with ab initio estimates of solute-solvent hydrogen bond energies.
TL;DR: In this paper, the 51 V NMR spectra have been obtained for vanadate and peroxovanadate complexes that exist at pH ≤ 7 in solutions containing 2-90% water in acetonitrile.
TL;DR: In this article, the influence of temperature on the protonation of acetonitrile by acidic zeolites was studied by infrared spectroscopy, and a new technique was presented for the study of the acidity of solids under reaction conditions.
Abstract: The influence of the temperature on the protonation of acetonitrile by acidic zeolites was studied by infrared spectroscopy. Acidity at room or low temperature was not correlated with the protonation temperature, but the zeolitic structure played an important role. A new technique is presented for the study of the acidity of solids under reaction conditions. A good correlation was obtained in a series of various zeolites between the catalytic activity in the cracking of n-hexane and the protonation temperature of acetonitrile.
TL;DR: In this article, it was shown that the type of the separation buffer and the conditions for the stacking of cationic versus anionic compounds are quite different and that the ionic strength of the buffer and addition of organic modifiers affected the stacking to a limited extent.
TL;DR: Simply mixing solutions of the title compound 1 and tetrathiafulvene in acetonitrile provides the charge-transfer complex 2, which functions as a novel electron acceptor and is present in the complex as a radical anion.
Abstract: Simply mixing solutions of the title compound 1 and tetrathiafulvene (TTF) in acetonitrile provides the charge-transfer complex 2. Here, 1 functions as a novel electron acceptor and is present in the complex as a radical anion. An electrical conductivity of up to 3 S cm-1 was determined for 2 with a two-point powder measurement.
TL;DR: In this article, functionalized cyclopentadithiophenes 2 and 3 were synthesized and polymerized by anodic coupling, in acetonitrile solution, in the presence of 0.1 M tetraethylammonium perchlorate as supporting electrolyte.
Abstract: Functionalized cyclopentadithiophenes 2 and 3 were synthesized and polymerized by anodic coupling, in acetonitrile solution, in the presence of 0.1 M tetraethylammonium perchlorate as supporting electrolyte. The former carries a 16-crown-5-ether ring coplanar to the bithiophene moiety, while a perpendicular 15-crown-5-ether ring is present in the latter. The cyclic voltammogram of poly-2 shows two redox processes at E° = −0.3 and +0.3 V, whereas that of poly-3 consists of a single response at E° = 0.0 V. The difference in electrochemical behavior is attributed to the occurrence of strong polaron π-dimerization in poly-2. The redox potential (E°) of this polymer moves toward more positive values passing from lithium to sodium salts as supporting electrolytes in acetonitrile solution. The redox cycle of poly-3 is instead completely insensitive to the change of the cationic species in solution. EQCM analysis shows that (i) both neutral polymers incorporate one alkaline ion per crown ring, (ii) the p-doping p...
TL;DR: In this article, the pore size governed dispersion interaction in MCM-41 molecular sieves has been investigated for the analysis of the adsorption heat of a non-polar molecule.
TL;DR: In this paper, the gas-phase hydrogenation of acetonitrile was studied with silica-supported platinum catalysts of which the degrees of metal dispersion were widely changed by reduction conditions.
Abstract: The gas-phase hydrogenation of acetonitrile was studied with silica-supported platinum catalysts of which the degrees of metal dispersion were widely changed by reduction conditions. The activities were found to decrease gradually during the course of reaction for all the catalysts examined. The initial rate of reaction increased with an increase in the degree of platinum dispersion, D. Triethylamine was the only main product irrespective of D and period of reaction time. The initial turnover frequency, TOF0, was shown to be smaller for larger D values. This dependence of TOF0 on D was explained by the electronic state of the surface of the platinum particles and the state of acetonitrile molecules adsorbed on them on the basis of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy measurements. The surface layer of smaller particles is more favorable for the adsorption of acetonitrile. The acetonitrile is adsorbed by platinum with the electron lone pair of nitrogen in the antibon...
TL;DR: In this article, the effect of the composition of binary mixtures of acetonitrile (ACN) and water (ranging up to 80%, v/v, ACN) on the apparent pKa values and actual mobilities of 26 aromatic substituted benzoic acids is investigated.
TL;DR: In this paper, a poly(1,3-dimethoxybenzene) was synthesized via the electrochemical oxidation of the corresponding monomer (1, 3-dimethylammonium tetrafluoroborate (Bu 4 NBF 4 ) and characterized spectroscopically.
TL;DR: The x-ray crystal structures of trans-cinnamoyl-subtilisin, an acyl-enzyme covalent intermediate of the serine protease subtilisin Carlsberg, have been determined to 2.2-A resolution in anhydrous acetonitrile and in water; thus, acylation in either aqueous or nonaqueous solvent causes no appreciable conformational changes.
Abstract: The x-ray crystal structures of trans-cinnamoyl-subtilisin, an acyl-enzyme covalent intermediate of the serine protease subtilisin Carlsberg, have been determined to 2.2-A resolution in anhydrous acetonitrile and in water. The cinnamoyl-subtilisin structures are virtually identical in the two solvents. In addition, their enzyme portions are nearly indistinguishable from previously determined structures of the free enzyme in acetonitrile and in water; thus, acylation in either aqueous or nonaqueous solvent causes no appreciable conformational changes. However, the locations of bound solvent molecules in the active site of the acyl- and free enzyme forms in acetonitrile and in water are distinct. Such differences in the active site solvation may contribute to the observed variations in enzymatic activities. On prolonged exposure to organic solvent or removal of interstitial solvent from the crystal lattice, the channels within enzyme crystals are shown to collapse, leading to a drop in the number of active sites accessible to the substrate. The mechanistic and preparative implications of our findings for enzymatic catalysis in organic solvents are discussed.
TL;DR: Three rhenium(V) oxo phosphine complexes and methyltrioxorhenium have been used as catalysts for oxidation of sulfides to sulfoxides with urea-hydrogen peroxide as oxidant in acetonitrile.