Showing papers on "Acetonitrile published in 1968"

Infrared Spectra of Acetonitrile and Acetonitrile‐d3

Abstract: The infrared spectra of acetonitrile and acetonitrile‐d3 have been studied at − 50°C for the high‐temperature (β) crystalline phase and at − 65°, − 115° and − 192°C for the low‐temperature (α) crystalline phase. A powder x‐ray pattern obtained at liquid‐nitrogen temperature indicates that the unit cell is primitive orthorhombic and that it contains eight molecules. It is shown that the consideration of all available structural data together with the site group and factor group splittings for the α crystal tends to favor D2h1 (Pmmm) and D2h9 (Pbam) as possible space groups.

A study of molecular re-orientation in liquid acetonitrile by nuclear spin-lattice relaxation

Abstract: Studies of the nitrogen, deuteron and proton relaxation rates of liquid acetonitrile at various temperatures were carried out by pulsed N.M.R. techniques. Re-orientation of the methyl group about its symmetry axis is found to be approximately ten times faster than the re-orientation of the nitrile group. Analysis of the data provides an example of a large room-temperature contribution to the intramolecular relaxation component by a spin-rotation interaction. Previously sizeable spin-rotation interactions were considered to be insignificant for organic molecules at room temperature.

The chemistry of rhenium–nitrile complexes

Abstract: Rhenium pentachloride is reduced by nitriles to tetrachlorobis(alkanonitrile)rhenium(IV). The oxidation product is an organic chloro-compound. Several new rhenium(IV) complexes were obtained by substitution or by addition of nucleophiles to the co-ordinated nitrile group. Addition of primary aromatic amines gives complexes of N-substituted amidines and of alcohols, complexes of imidate esters. Reduction of the complex ReCl4(MeCN)2 gives the tetrachlorobis(acetonitrile)rhenate(III) ion, which has been isolated in crystalline salts. Malononitrile reacts with trans-ReOCl3(PPh3)2 to give trichloro-[4-(dicyanomethylene)azetid-2-imine]bis(triphenylphosphine)-rhenium(III); this complex with ammonia gives a novel ammine salt.

An N.M.R. study of complexes in acetonitrile solutions of aluminium chloride

Abstract: High resolution proton N.M.R. and broadline 27Al N.M.R. studies have been made in very pure 1 M AlCl3/acetonitrile (AN) solutions containing various concentrations of LiCl. In addition to the observation of additional peaks in the proton spectrum due to coordination of AN, two aluminium resonances were found in 1 M AlCl3/AN. These two resonances are interpreted in terms of two aluminium containing species, one of which coordinates with acetonitrile, while the other is a Cl- complex. Addition of LiCl to 1 M AlCl3/AN decreases the population of the coordinating species relative to the non-coordinating species, showing that the Cl- complexing interaction is stronger than the coordination interaction. This information has been used in determining the coordination number of Al3+ ions in 1 M AlCl3/acetonitrile.

Redox transfer. Part V. Elementary steps. The oxidation of ferrous and cuprous chloride by carbon tetrachloride

Abstract: The oxidation of ferrous chloride by carbon tetrachloride has been studied spectrophotometrically by initial-rate measurements of FeCl4– formation in acetonitrile as solvent and in the presence of an excess of chloride ion. A transient violet intermediate appears upon mixing of the reagents, considered to be a charge-transfer complex between ferrous chloride and carbon tetrachloride, which decomposes into FeCl4– and a trichloromethyl radical. This decomposition is the rate-determining step in the overall oxidation to ferric chloride. Trichloromethyl radicals are captured by ferrous chloride in a subsequent fast reaction, giving a carbenoid complex which decomposes bimolecularly into ferric chloride and tetrachloroethylene. in the presence of an olefin, dichlorocyclopropanes are also formed. The overall reaction is first-order in ferrous chloride and has a rate constant of 2·10–4l. mole–1 sec.–1 at 22°. The fast interaction of ferrous chloride and trichloromethyl radicals, and the subsequent reactions of the complex formed, are recognized as the main mode of termination in the radical-chain addition of carbon tetrachloride to olefins in a redox transfer-system. The rate constant of the reaction between cuprous chloride and carbon tetrachloride (CCl4+ CuCl[graphic omitted]CuCl2+·CCl3) is about 40 times smaller than the corresponding constant for the ferrous chloride reaction. The reaction reaches a quasi-equilibrium already at conversions into cupric chloride as low as 1·5%.

Solvent effects on the boron–fluorine coupling constant and on fluorine exchange in the tetrafluoroborate anion

Abstract: The 11B—19F spin–spin coupling constant in AgBF4 is shown to have an opposite sign in water from that found in a number of organic solvents. Application of the hypothesis of Bell and Danyluk indicates that it has a positive sign in water. Evidence is presented for association, probably in the form of solvent-separated ion pairs, in aqueous LiBF4 and NaBF4 solutions, and for the formation of more tightly bound ion pairs in solvents of lower dielectric constant. In contrast, there apparently is no solute association in AgBF4 solutions in water, DMSO, DMF, or acetonitrile. The pronounced changes observed in the 11B—19F coupling constant support the postulate that its small size is a result of near cancellation of large opposing terms.The collapse of the 10B—11B isotope shift at high temperatures in the 19F spectra of solutions of AgBF4 in acetonitrile and in acetone provides evidence for exchange of fluorine among boron atoms; a mechanism is proposed for this process.

Infrared and Raman spectra of solutions of zinc, cadmium, and mercury(II) nitrates in acetonitrile

Abstract: Infrared and Raman spectra are reported for acetonitrile solutions of zinc, cadmium, and mercury(II) nitrates and some of their halides. The nitrate spectra are, in each case, consistent with strong perturbation of nitrate ions by solvated cations, but only in the case of mercury(II) has a metal–oxygen vibration frequency been observed. This is discussed in terms of the lower stability of the mercury(II) compound. Examination of the perturbation of the vibrational spectra of free acetonitrile caused by co-ordination to zinc shows that the C–N stretching frequency is increased by ca. 40 cm.–1 rather than 63 cm.–1 as previously reported. Raman intensity studies of the relation between Zn(NO3)2 concentration and the C–N band intensity of acetonitrile establish that in concentrated solutions the principal zinc species present is [Zn(CH3CN)2](NO3)2.

Kinetics of the Reversible Hydration of 1,3-Dichloroacetone in Dioxan and Acetonitrile Solution

Abstract: The kinetics of the reversible hydration of 1, 3-dichloroacetone have been studied spectrophotometrically in solutions of water in dioxan and in acetonitrile, over a wide range of water concentrations, with and without the addition of catalysts. The results in both solvents strongly suggest that in the uncatalysed reaction the transition state contains one molecule of ketone and three molecules of water; in the catalysed reaction a molecule of triethylamine or benzoic acid can replace one or two molecules of water respectively. A cyclic transition state is proposed, and model calculations suggest that the reaction takes place by the step-wise transfer of three protons rather than by their synchronous motion. The same conclusion is reached by considering the observed kinetic hydrogen isotope effect of k H / k D = 2·7.

Carbonyl insertion reactions of methyl- and ethyl-tricarbonylcyclopentadienylmolybdenum

Abstract: Methyl- or ethyl-tricarbonylcyclopentadienylmolybdenum reacts in acetonitrile with a variety of phosphines and phosphites to afford the stable crystalline acyl complexes RCOMo(CO)2(L)π-C5H5. The reactivity sequence Et > Me is observed, and rate studies with the methyl compound in acetonitrile show that the rate of reaction is independent of ligand and ligand concentration. In chloroform as solvent, the ethyl compound reacts with phosphorus ligands by simultaneous first- and second-order reactions. Arsenic, sulphur, or pyridine ligands do not react.The mechanism and stereochemistry of these reactions is discussed in the light of infrared and 1H n.m.r. spectroscopic measurements.

Magnetism, electronic spectra, and structure of transition metal alkoxides. VI. Chromium(III) chloro alkoxides

Abstract: In the compound Cr(OMe)C12,2CH3OH one molecule of methanol can be replaced by one molecule of acetone, acetonitrile, or dioxan. The magnetism and spectra are interpreted in terms of dimeric models. On heating the dimethanolate one molecule of methanol is lost and for this compound a tetrameric structure is proposed.

The Cobalt Carbonyl-catalyzed Intramolecular Hydroesterification of Allyl Alcohol with Carbon Monoxide

Abstract: The intramolecular hydroesterification of allyl alcohol with carbon monoxide to give γ-butyrolactone occurred in the presence of cobalt carbonyl under the pressure of carbon monoxide containing a small amount of hydrogen; propionaldehyde and isobutyraldehyde were produced as by-products The selectivity toward γ-butyrolactone increased with the use of acetonitrile or its derivatives as the solvent The addition of pyridine, in the absence of these solvents, was effective only in increasing the reaction rate, not in increasing the selectivity toward γ-butyrolactone On the other hand, in the presence of acetonitrile as a solvent, the selectivity toward γ-butyrolactone increased together with the reaction rate when a catalytic amount of an organic base such as pyridine was added The higher the reaction temperature, the higher the pressure necessary to attain a maximum selectivity toward γ-butyrolactone; the best yield of γ-butyrolactone was ca 60% The effect of the partial pressures of hydrogen and carbo