Showing papers on "Ionic liquid published in 1983"

Increased Electrochemical Window in Ambient Temperature Neutral Ionic Liquids

Abstract: : A neutral melt of exactly 1.0:1.0 mole composition of AlCl3:RC1, where R(+) is either N-(1-butyl) pyridinium or 1-methyl-3-ethyl imidazolium, has been shown to have an increased electromechanical window of 3.5 an 4.5 V, respectively. System characteristics are described.

Molybdenum chloro complexes in room-temperature chloroaluminate ionic liquids: stabilization of [MoCl6]2− and [MoCl6]3−

Abstract: Donnees electrochimiques et spectrales indiquant la formation de solutions stables des ions [MoCl 6 ] 2− et [MoCl 6 ] 3− . On observe une instabilite du Mo(V) dans la masse fondue basique

Copper(I) and copper(II) chloro complexes in the basic aluminum chloride-1-methyl-3-ethylimidazolium chloride ionic liquid

Abstract: Cu(I) forme des complexes chloro mononucleaires tris stables de type CuCl 1 1−p : a 40°C les especes principales sont CuCl 2 − et CuCl 4 3− . Consstantes de stabilite

Voltammetric determination of water in an aluminum chloride-N-n-butylpyridinium chloride ionic liquid

Abstract: L'eau, dans un sel fondu a la temperature ambiante constitue de chlorures d'aluminium et de N-n-butylpyridinium donne une vague de reduction controlee par la diffusion convective, a une electrode a disque de platine tournant, qui peut etre utilisee pour l'analyse

Thermodynamics and structures in solvents coordinating through nitrogen. I. Enthalpies of transfer from water to pyridine and acetonitrile for some monovalent cations and anions

Abstract: The enthalpies of transfer ΔHtro, between water and the aprotic solvents pyridine and acetonitrile have been determined for a number of 1-1 electrolytes. To calculate ΔHtro for the single ions, the tatb assumption that ΔHtro,(Ph4As+) = ΔHtroBPh4-) for all solvents has been applied. The results are compared with those found earlier for the transfer between water and dimethyl sulfoxide. The values of ΔHtro, differ widely between different ions, from exothermic by c. 30 kJ/mol to endothermic by about the same amount. Endothermic values are found for Cl- and, though much smaller, for Br-, and also for the large tetraalkylammonium ion Bu4N+. Compared to the differences in ΔHtro, found between the various ions, the differences found for a certain ion between different solvents are small. The decrease of AH,", in the sequence Cl- > Br- > I- runs almost parallel in the three aprotic solvents, and is much less steep than in water. This reflects the influence of ligand hydrogen bonding in the protic solvent.

A multinuclear magnetic resonance study of the tetraphenylarsonium and tetraphenylphosphonium tetraphenylborates in nonaqueous solvents

Abstract: Arsenic-75, phosphorus-31, boron-11, carbon-13 and lH n.m.r. measurements are reported for Ph4As+, Ph4P+ and Ph4B- ions in a number of nonaqueous solvents. The resonance frequencies of the first three nuclei are very nearly independent of the solvent and of the salt concentration indicating an effective shielding of the central atom from the solvent by the four phenyl groups. In contrast the resonance frequencies of the ortho, meta and para carbons and protons of the phenyl rings vary with the solvent. The resonances of the cationic and the anionic carbons and protons are different and the differences are solvent-dependent. The results indicate that the two cations and the anion are solvated to a different extent and that the 'reference electrolyte' assumption, used to obtain single ion transfer activity coefficients, has to be used cautiously.

Resonance and solvent effects on absorption spectra of some 2- and 4-(–M)-substituted aniline derivatives

Abstract: The N-H protons of N-methyl-2-X-aniline derivatives remain intramolecularly hydrogen bonded in HBA (hydrogen bond acceptor) solvents where X = COOMe and NO2, but form intermolecular hydrogen bonds to the HBA solvents where X = CN. The order of response of vmax to solvent HBA basicity for the Cl → C2 bands of N-unsubstituted-2-(-M)-substituted aniline derivatives and the Cl → C4 bands of 4-(-M)-substituted aniline derivatives follows the orders of the hydrogen bond donor acidities of the amine protons, which are determined primarily by the mesomeric effects of the 2- and 4-substituents. The spectral data indicate that intramolecularly hydrogen bonded 2-(-M)-substituted aniline derivatives are near sp2 hybridized in non-HBA solvents and, unlike several 4-substitute anilines, do not undergo significant rehybridization in HBA solvents. Bath ochromic shifts resulting from hydrogen bonds by corresponding 2- and 4-substituted aniline derivatives to HBA solvents are of similar magnitudes.

Thermotropic ionic liquid crystals. 3. Sodium-23 nuclear magnetic resonance study of the ionic mesophase of sodium n-alkyl carboxylates

Abstract: Interpretation des resultats en terme de mouvement anisotropique des ions Na + et RCOO − dans la mesophase et de mouvement libre dans la phase isotrope

Liquid junction potentials across the interface between the aqueous saturated calomel electrode and some nonaqueous solvents, based on the tatb assumption

Abstract: The liquid junction potentials (Ej) across aqueous saturated KCl/nonaqueous solvent junctions have been determined within the framework of the tetraphenylarsonium tetraphenylborate (tatb) extra- thermodynamic assumption. The nonaqueous solvents comprise methanol, ethylene glycol, acetonitrile, propylene carbonate, dimethylformamide and dimethyl sulfoxide. The Ej values obtained are fairly small (below 40 mV) in the case of protic solvents and fairly large (within 100-200 mV) in the case of dipolar aprotic solvents, as expected if primarily guided by solvent-solvent interactions across the liquid junctions. The results allow the aqueous saturated calomel electrode to be used to relate electrode potentials in different solvents.

Preparation and Copolymerization of Methacrylate-Terminated Ionic Liquid Rubbers

Abstract: Preparation of methacrylate-terminated ionic liquid rubbers (MTILR) was investigated by the addition reaction of partially neutralized carboxyl-terminated liquid rubbers (PNCTLR) with glycidyl methacrylate. The PNCTLR were prepared from a polymer of butadiene (BD) (Hycar CTB 2000X162) and a copolymer of BD-acrylonitrile (Hycar CTBN 1300X8) by partial neutralization with MgO and CaO. The metal carboxylate groups of PNCTLR catalyzed the reaction. The Mg carboxylate group showed higher catalytic activities than the Ca carboxylate group. The MTILR obtained were copolymerized with styrene. The novel ionic copolymers obtained were evaluated for their physical properties. The copolymers containing Mg showed better physical properties than their reference copolymers not containing ionic links, an effect of introducing metal. The Ca-containing copolymers showed poor physical properties, probably due to lower interionic attraction of Ca2+, to heterogeneity of the systems, and to lower overall cross-linking...

Colloidal platinum sols: anion effects on coagulation behaviour

Abstract: The concentration of added electrolyte required to induce coagulation of a platinum sol has been determined for a range of electrolytes. It has been found that, for electrolytes in which the anion contains lone-electron-pair substituents, sol stability is significantly enhanced compared with that observed when similar but non-electron-pair-containing anions are used. It is proposed that the lone electron pairs enable anion adsorption on negative platinum surfaces despite the Coulombic repulsions present.

Thermotropic ionic liquid crystals. II. 1H and 23Na NMR study of the smectic mesophase of molten sodium n‐butyrate and sodium isovalerate

Abstract: The 1H and 23Na NMR studies of smectic ionic mesophases of molten sodium n‐butyrate and sodium isovalerate are reported over the temperature range of the stability of the liquid crystalline phases The 1H spin‐lattice relaxation times T1 at ν0=92, 243, and 60 MHz for the anions of both the systems are interpreted in terms of diffusion intermolecular relaxation mechanism The predicted anion diffusion coefficients are in agreement with those measured directly by spin‐echo technique and indicate that the anion diffuses rapidly In contrast to the T1 relaxation mechanism the results obtained for the proton relaxation times in the rotating coordinate frame T1ρ indicate that the order‐fluctuation relaxation mechanism determines the frequency dispersion of T1ρ The analysis of the T1ρ data provides an approximate measure of the order parameter S as a function of temperature Fourier transform spectra of the 23Na transitions show that the electric field gradient (EFG) at the Na+ ion is nonaveraged and of such

Radical and ionic nucleophilic substitution reactions on α-Alkyl-γ-(p-nitrophenyl)allyl derivatives

Abstract: The nature of the reaction between α-alkyl-γ-(p-nitrophenyl)allyl chlorides (1)-(3), which have the general form p-O2NC6H4CH=CHCH(Cl)R, and a variety of nucleophiles depends on the alkyl group R and the nucleophile. The chloride (1) (R = Me) undergoes ionic (SN2 and subsequent Michael addition) processes with the salt (7) of 2-nitropropane to give products (15) and (16) whereas the chloride (2) (R = Pr1) gives a mixture of products (17) and (18) which are shown to arise by a radical-chain nucleophilic substitution process, with allylic rearrangement-an SRNl' reaction-and ionic processes respectively. The chloride (3) (R = But) gives the SRN1' product (25) with the salt (7). Other nucleophiles with (2) and (3) appear to react by ionic (SN2 and SN2') and/or SRNl' processes; e.g. (3) gives an excellent yield of the malononitrile (32) by an SN2' process when treated with the sodium salt (9).

Adsorption properties and stability of dihexadecyl phosphate vesicles

Abstract: The adsorption of the photochemical sensitizer tris(2,2'-bipyridine)ruthenium(II) on dihexadecylphosphate vesicles has been determined as a function of the pH and ionic strength of the dispersing medium. The adsorption density is a maximum at pH 7.5 ± 0.5 and with minimum ionic strength(pH adjusted by adding NaOH). The stability of the vesicles with respect to flocculation, in the presence of adsorbed sensitizer, is increased when the pH is raised from 3.3 to 7.5. The presence of an amine buffer at 5 x 10-2 at pH 7.8 reduces the adsorption density by more than 90%. The relevance of these results to the interpretation of photochemistry experiments (in conjunction with photochemical hydrogen production from water) is discussed.

An Incomplete-Dissociation Model for Diffusion and Ionic Conduction in Pure Molten Salts

Abstract: Diffusion and ionic conduction in pure 1:1 molten salts is described by an incomplete-dissociation model comprising neutral diatomic molecules and monoatomic ions. The internal mobility b+- and the self-diffusion coefficients D+ and D- are given in terms of the six interparticle friction coefficients and the degree of dissociation. By an approximation it is possible to derive from experimental D+ and D- values an apparent degree of dissociation which ranges from 0.93 for NaCl to 0.51 for TlCl and decreases with temperature.

Estimation of transfer activity coefficients for single ions between dipolar aprotic solvents from the E.M.F. of cells with liquid junction

Abstract: Transfer activity coefficients for the sodium ion, logmγNa, between pairs of dipolar aprotic solvents were estimated from the e.m.f. of cells consisting of two sodium-selective electrodes in different solvents connected by a salt-bridge of triisoamylbutylammonium tetraphenylborate [(tab+)BPh4-], or tetraethylammonium picrate (Et4NPic), or tetraethylammonium perchlorate (Et4NclO4). The solvents were: acetonitrile (MeCN), N,N-dimethylformamide (HCONMe2), dimethyl sulfoxide (Me2SO), propylene carbonate (pcar), and N-methylformamide (HCONHMe). Values of logmγNA were estimated first by neglecting the liquid-junction potential E, and then, for some systems, by applying an Ej correction from theory. A novel method of estimating transfer activity coefficients for single ions, based on the Ej equation, was demonstrated on the (tab+) and Pic-ions. Transfer activity coefficients for the hydrogen ion between MeCN and HCONMe2 as well as MeCN and Me2SO were similarly estimated from the e.m.f. of two pH (glass) electrodes immersed in buffer media in the above pairs of solvents.

Electron-transfer reactions in non-aqueous media. VII. Reduction of CoF(NH3)52+ and Co(HCOO)(NH3)52+ by copper(I) in dimethyl sulfoxide-water mixtures

Abstract: Previous work on the reduction of a series of cobalt(III) complexes by iron(II) in dipolar aprotic solvents and in aqueous mixtures has been extended to reduction by copper(I). The greater stability of copper(I) to disproportionation in these media has permitted the study of the reduction of CoF(NH3)52+ and Co(HCOO)(NH3)52+ in range of solvents over a number of temperatures with a precision not possible in previous studies in water. The results are consistent with an inner-sphere mechanism in which the copper(I) reductant is preferentially solvated by dimethyl sulfoxide to the exclusion of water in mixed solvents.

Ligand substitution kinetics of iron(III) in aprotic solvents

Abstract: The complexation reactions of NCS- and Br- with iron(III) have been studied in N,N-dimethyl-formamide, and the temperature activation parameters determined. The observed forward rate constants are 114±5 and 69±31, mol-1 s-1, the activation enthalpies are 48+±3 and 74±4 kJ mol-1, and the activation entropies are -45±8 and 40±10 J K-1 mol-1, respectively, at 298 K and 0.5 M ionic strength. The complexation reactions of NCS- with iron(III) in dimethyl sulfoxide have been studied at ionic strengths of 0.1, 0.3 and 0.5 M, and over a range of temperatures. The observed forward rate constant is 55±31. Mol-1 s-1, the activation enthalpy is 42±3 kJ mol-1, and the activation entropy is -70±30 J K-1 mol-1 at 298 K and 0.5 M ionic strength. It is proposed that the substitution reactions of iron(111) in the aprotic solvents N,N-dimethyl- formamide and dimethyl sulfoxide proceed through an associative interchange (Ia) mechanism.

Some common problems concerning solvent polarization and dielectric behaviour at ions and electrode interfaces

Abstract: The sensitivity of the dependence of ionic hydration properties of simple cations and anions on ionic radius is compared and related to the dielectric polarization in the solvent, near the ion. Corresponding dielectric polarization of the water solvent in the interphase at the surface of charged electrodes is evaluated on the basis of several models of oriented water dipoles at electrodes and compared with the situation at ions. It is pointed out that previous theories of the double-layer at electrodes have considered either the solvent polarization in the absence of adsorbed ions or the behaviour of ions independently of the solvent polarization by the electrode surface charge. Calculations are given that indicate that the surface concentrations of adsorbed ions at electrodes are commonly sufficient to cause a major influence on the behaviour of interphasial water in addition to that arising from the effect of electrode surface charge. Further, repulsion, due to overlap of Gurney cospheres of ions, will be an important factor in ionic interactions laterally within the double-layer.