Formamide Solvent Research Articles

ACID DISSOCIATION BEHAVIOR OF 2, 3- AND 2, 3, 9,lO-METHYL- OR CYCLOHEXYL-SUBSTITUTED CYCLAMS, THEIR COMPLEXATION BEHAVIOR WITH COPPER@) AND THE AXIAL SOLVENT SPECTRUM OF THEIR COMPLEXESINTERACTION EFFECT ON THE LIGAND-FIELD

Stability constants of Cu(Il)-complexes for 1, 4, 8, 11-tetra-azacyclotetradecane (cyclam) analogs with periphery substituted [14]aneN4-ring, 2, 3-tetramethyl-, 2, 3, 9, 10-octamethyl-, 2, 3-cyclohexyl, and 2, 3, 9, 10-dicyclohexyl-cyclams have been determined at 25°C in aqueous solution. The UV-Vis absorption spectra of their complexes, ([Cu(L)] (C1O4)2), were measured in water and some typical organic solvents (methanol, acetone, propylene carbonate, formamide, N, N-dimethylformamide, and dimethylsulfoxide). A good linear relationship was found between the stability constant logKCuL) and the difference between the wavenumber of maximum absorption in water and in the organic solvents (δλmax −1 (W-S)). The value of logKCuL at δλmax −1(W-S) = 0 not only shows a linear relation to solvent parameters, donor number and dielectric constant, but also to the enthalpy of transfer of ClO4 − from water to the organic solvents. The value is proposed as a new solvent parameter ‘Kλlue’ to be used as an index for solvent-effects on Cu(II)-complexes of cyclam analogs. The increasing order of the new parameter (log scale) is as follows; DMF(27.24)>DMSO(27.14)>FA(26.82)>MeOH(26.27)>PC(25.75)>AC(24.71). Another meaning of the new parameter is assumed from connection of the potentiometric data with spectrometric data. The solvent effects on stability and the UV-Vis spectra are assumed to be caused by perturbation of the D4 h or axially-elongated ligand field through axial approach of solvent to the Cu(II)-complexes and by formation of a solvent-separated ion pair between a solvated Cu(lI)-complex cation and counter anion (ClO4)

The static and dynamic surface composition of formamide-benzyl alcohol and water-formamide liquid mixtures studied by means of HeI photoelectron spectroscopy

The free surfaces of two binary liquid mixture systems over the whole range of bulk molar composition have been studied using HeI photoelectron spectroscopy in a thin, fast flowing jet arrangement. The spectra of the first group of mixtures, benzyl alcohol and formamide, are found to be deconvolutable by a weighted sum of the pure component spectra. Slight deviations in the procedure allow an estimate to be made of the surface orientation of single benzyl alcohol molecules on top of the formamide solvent. The relative surface composition in the top layer is extracted by the deconvolution procedure. Time relaxation of the surface composition is observed with time constants of the order of several tens of mus. The results of the second group of mixtures, water and formamide, show more complicated features, with one component rapidly evaporating on the time scale of the experiment. The relative surface composition is estimated by a constrained deconvolution involving mainly the first two ionization bands of the components. The location of individual peak structures changes markedly with the mixture composition ratio. The energy values of the first ionization bands indicate a solvent-solvate transition near a 2:1 to 3:1 bulk molar fraction of water. Time relaxation of the surface composition is observed also in these mixtures.

Muon Spectroscopy Applied to Biological Systems: A Study of Thiyl Radicals, RS

Thiyl radicals (RS.) are formed when positive muons (μ+) are implanted into solutions of thiocarbonyl compounds (C = S) in ethanol, tetrahydrofuran or formamide solvents. A solvent dependence is found, which reflects changing electronic interactions and overall conformations, suggesting that the properties of RS. radicals may be dependent on the polarity (philicity) of the environment in which they are formed.

Tetrabutylammoniumiodide in formamide and hydroxypropionitrile: the temperature dependence of segregation studied by metastable induced electron spectroscopy

Metastable induced electron spectroscopy is used to investigate the surface segregation of tetrabutylammoniumiodide in the solvents formamide and hydroxypropionitrile. In formamide no temperature dependence of the amount of salt found in the topmost surface layer can be traced. The segregation in hydroxypropionitrile is favoured by low solvent temperatures. Comparing the given bulk concentration with the particle ratio in the surface shows a larger enhancement in formamide. With the aid of surface tension measurements and under the assumption of a simple depth profile it is possible to estimate the thickness of the surface layer with an enhanced salt concentration.

The concentration-depth profile at the surface of a solution of tetrabutylammonium iodide in formamide, based on angle-resolved photoelectron spectroscopy

We have investigated a solution of tetrabutylammonium iodide (TBAI) in the polar solvent formamide (FA) using angle-resolved photoelectron spectroscopy at the Berlin Electron Storage Ring for Synchrotron Radiation (BESSY). The concentration was set to 0.5 molality. We have evaluated the signals from C 1s pertaining to TBAI and FA separately, varying the photon energy between 310 and 540 eV as well as the e-emission angle with respect to the surface normal. The combination of these data with earlier results from ARXPS obtained by Siegbahn and co-workers allowed us to establish a concentration-depth profile of the surface-active salt TBAI. For this purpose we have employed a new theoretical formulation and developed a new elaborate fitting program based on a genetic algorithm. The concentration of the salt could be followed down to a depth of about 45 AA below the surface. Cross sections for the inelastic energy loss of electrons in the liquid could be established as a function of electron energy. Comparison with conventional surface tension measurements allowed us to derive absolute values for the cross sections.

The investigation of liquid surfaces by electron spectroscopy

We evaluate electron spectrometric data taken from the surface of the solution of 0.5m tetrabutylammoniumiodide in the polar solvent formamide. In agreement with expectation we find strong enhancement of the salt in the topmost layer of the liquid. We describe how to derive the segregation depth profile of the salt making use of the fact that different electron spectroscopies lead to different observation depths. In addition we show how mean free paths of electrons in liquids can be determined with unprecedented accuracy by combining electron spectroscopy and conventional techniques like surface tension measurements.

Range of the solvation pressure between lipid membranes: dependence on the packing density of solvent molecules.

Well-ordered multilamellar arrays of liquid-crystalline phosphatidylcholine and equimolar phosphatidylcholine-cholesterol bilayers have been formed in the nonaqueous solvents formamide and 1,3-propanediol. The organization of these bilayers and the interactions between apposing bilayer surfaces have been investigated by X-ray diffraction analysis of liposomes compressed by applied osmotic pressures up to 6 X 10(7) dyn/cm2 (60 atm). The structure of egg phosphatidylcholine (EPC) bilayers in these solvents is quite different than in water, with the bilayer thickness being largest in water, 3 A narrower in formamide, and 6 A narrower in 1,3-propanediol. The incorporation of equimolar cholesterol increases the thickness of EPC bilayers immersed in each solvent, by over 10 A in the case of 1,3-propanediol. The osmotic pressures of various concentrations of the neutral polymer poly(vinylpyrrolidone) dissolved in formamide or 1,3-propanediol have been measured with a custom-built membrane osmometer. These measurements are used to obtain the distance dependence of the repulsive solvation pressure between apposing bilayer surfaces. For each solvent, the solvation pressure decreases exponentially with distance between bilayer surfaces. However, for both EPC and EPC-cholesterol bilayers, the decay length and magnitude of this repulsive pressure strongly depend on the solvent. The decay length for EPC bilayers in water, formamide, and 1,3-propanediol is found to be 1.7, 2.4, and 2.6 A, respectively, whereas the decay length for equimolar EPC-cholesterol bilayers in water, formamide, and 1,3-propanediol is found to be 2.1, 2.9, and 3.1 A, respectively. These data indicate that the decay length is inversely proportional to the cube root of the number of solvent molecules per unit volume.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of the halide electrolyte on the electrochemical reduction pathway of some meso-tetrasubstituted porphyrin free bases in N, N-dimethyl formamide

Differential pulse, cyclic and rotating disc voltammetry have been used to study the redox properties of meso-tetra-n-propylporphyrin (TPrP), meso-tetramethylporphyrin (TMP) and meso-tetraphenyl-porphyrin (TPP) at glassy carbon electrodes in tetraalkylammonium electrolyte in N,N-dimethyl form-amide solvent. Electrochemical reduction of the porphyrins is affected by the electrolyte employed. There is a large influence from the electrolyte anion and only a small one from the cation, shown by the difference in half-wave reduction potentials between tetrabutylammonium and tetraethylammonium electrolytes, both effects independent of the electrode material being glassy carbon or mercury. A systematic study on the influence of the anion was undertaken using TPrP and TPP in halide (chloride, bromide and iodide) salts of tetrabutylammonium electrolytes, including variation of the quantity of halide ion present, the behaviour in 0.1 M tetrabutylammonium perchlorate being taken as the reference. Trends in half-wave potential and wave shape from chloride to perchlorate are more accentuated for TPrP than for TPP. UV-visible spectra of the porphyrins were found to be electrolyte invariant. Rationalisation in terms of interaction between the porphyrin mononegative ion and the halide ion providing an alternative, anion concentration dependent, reduction pathway is discussed.

Gamma-ray resonance spectroscopic study of MoS2- and iron-based catalysts

1. A gamma-resonance spectroscopic study has been made of systems obtained by impregnating molybdenum disulfide samples with solutions of57Fe(NO3)3·9H2O in different solvents (formamide, acetone, water) and subsequently sulfidizing them. After a catalyst is sulfidized, most of the iron is in the form of magnetic sulfides, and the remainder is present in the form of the paramagnetic ions Fe2+ and Fe3+. 2. The catalytic activity of these systems in the hydrogenation of o-xylene in the presence of thiophene, which depends on the type of solvent, is due to the paramagnetic iron ions that form a structure in combination with the MoS2; the activity increases with increasing amounts of Fe3+ ions.

Selective modification of sodium channel gating by solvents and drugs

In Myxicola heavy water (D 2O) does not alter Na + gating currents, but slows activation and inactivation. In this study, the solvent formamide (5–20% v/v) is shown to proportionately and reversibly block Na + currents and charge movement, suggesting it may be useful for fractionating gating currents. Formamide- and prepulse-sensitive (inactivating) gating currents were identical, comprising 60–80% of total charge. Both had rising phases and decayed as single exponential functions. Formamide-insensitive and non-inactivating charge movements had no rising phases and decayed slowly with more complex kinetics. Another solvent, dimethylsufoxide (1% v/v), had no effect on Na + activation or charge movement, though it did affect inactivation. Amantadine (0.1 mM) did not charge Na + activation or charge movement, but slowed inactivation and shifted the foot of the steady state Na + inactivation curve. Sotalol (0.1 mM) slowed inactivation, but also inhibited Na + activation and gating current.

Methylene blue as a retarder of free radical polymerization: 1. Polymerization of acrylonitrile, methyl methacrylate and styrene

Methylene blue (MB), a redox dye, in monomeric form significantly retards the free radical polymerization of styrene (ST) and acrylonitrile (AN) in N, N-dimethyl formamide solvent. The effect is small in methyl methacrylate (MMA) polymerization. Partly reduced MB is found to be a stronger retarder than MB. The rate constants for the oxidation of the polymer radicals by MB at 60°C follows the order ST>AN>MMA. The results cannot be explained when only taking into consideration the reactivity and polarity parameters of the radicals and the substrate, as is done in the Q-e scheme. The low rate constant with the PMMA radical is attributed to steric effects. The current work has shown that single molecules of MB are effective chain terminators and this is in sharp contrast with the conclusion reached by Chen who postulated that only the aggregates of MB are the chain terminators in the polymerization of acrylamide in water.

Calculations on ionic solvation. Part 6.—Structure-making and structure-breaking effects of alkali halide ions from electrostatic entropies of solvation. Correlation with viscosity B-coefficients, nuclear magnetic resonance B′-coefficients and partial molal volumes

The electrostatic entropy of solvation of an ion, ΔS°e, or the contribution to ΔS°e from the co-ordination sphere of the ion, ΔSI, II, have been shown to be quantitative measures of the structure-making and structure-breaking effects of ions of the alkali halide series in water and in non-aqueous solvents. Both entropy criteria indicate that in water the ions Li+, Na+, Ag+ and F– are net structure-makers, the ions Rb+, Cs+, Cl–, Br–, I– and ClO–4 are structure-breakers, and K+ is a borderline case. In the non-aqueous solvents formamide, methanol, N-methylformamide, dimethylformamide, dimethylsulphoxide and acetonitrile, all the above ions are structure-makers with the exceptions of the weak structure-breaking ion ClO–4 in formamide and the borderline cases of ClO–4 in methanol and I– in formamide.It is shown that the ΔS°e or ΔS°I, II values may be used to assign single-ion B- or B′-coefficients and that for water and several non-aqueous solvents there are good linear correlations between the entropy values and the single-ion coefficients. There are also good linear correlations between the entropy values and single-ion text-decoration:overlineV° values when the latter are based on text-decoration:overlineV°(H+, aq, 1 mol dm–3)=–5.4 cm3 mol–1 and when values of text-decoration:overlineV° in non-aqueous solvents are assigned by the correspondence method. It is further shown that the general conclusions reached do not depend on any particular choice of ionic radii, although the Goldschmidt–Pauling set is preferred, and it is suggested that the derived ΔS°e and ΔS°I, II values are close to ‘absolute’ values and hence provide an ‘absolute’ measure of ion–solvent interactions.

Polarographic and voltammetric studies of tetrabutylammonium hexacyanoferrate(III) and tetrabutylammonium hexacyanomanganate(III) in non-aqueous solvents

Tetrabutylammonium hexacyanomanganate(III) [(bu 4N) 3Mn(CN) 6] has been studied by polarography and cyclic voltammetry in formamide, methanol, ethanol, N-methylformamide, dichloromethane, dimethylsulfoxide, acetonitrile, N,N-dimethylformamide, propylenecarbonate, butyrolactone, N-methylthiopyrrolidone(2), N,N-dimethylthioformamide, 1.2-dichloroethane, N-methylpyrrolidone(2) and tetramethylenesulfone. Similar studies have been carried out for tetrabutylammonium hexacyanoferrate(III) [(bu 4N) 3 Fe(CN) 6] in the solvents formamide, N-methylformamide, dichloromethane, butyrolactone, N-methylthiopyrrolidone(2) and tetramethylenesulfone. The half-wave potentials of the reductions (bu 4N) 3Mn(CN) 6 to (bu 4N) 4Mn(CN) 6 and (bu 4N) 3Fe(CN) 6 to (bu 4N) 4Fe(CN) 6 versus bisbiphenylchromium(I)/bisbiphenylchromium(0) as a reference redox system were found to vary with the nature of the solvent. Comparison with data previously obtained for the respective tetraethylammonium salts of hexacyanoferrate(III) and hexacyanomanganate(III) have shown that the redox behaviour of these compounds is influenced by both the solvent and the tetraalkylammonium ions. Correlations exist between the half-wave potentials of (bu 4N) 3Mn(CN) 6 and (bu 4N) 3Fe(CN) 6 and both the acceptor number of the solvents and the free enthalpies of transfer of the chloride ion. The results are discussed in the concept of donor-acceptor interactions.

Stability of mercurated DNA during reassociation and S 1 nuclease digestion experiments

The stability of covalently mercurated DNAs during DNA:DNA reassociation, heteroduplex recovery on sulfhydryl-Sepharose, and S 1 nuclease digestion under a variety of solvent and temperature conditions is described. The nonspecific loss of 203Hg from mercurated DNA can be minimized by use of aqueous formamide solvents in reassociation experiments and by minimizing exposure to sulfhydryl reagents and temperatures above 35°C. Single-stranded DNA is shown to be more sensitive to demercuration than is native, duplex DNA.

The dielectric properties of formamide, ethanediol and methanol

The dielectric properties of the solvents formamide, ethanediol and methanol have been studied over a frequency range of 10 MHz-70 GHz and a temperature range of 10-40 degrees C. It was found that formamide is best represented by a single Debye type dispersion, ethanediol by a double Debye and methanol by a Cole-Cole distribution of relaxation times.

Molecular weight of an extremely hydrophobic protein, zein, in dimethylformamide and in formamide.

Both alpha zein purified from a commericial preparation and beta zein prepared fresh from corn are soluble in the nonaqueous solvents formamide and dimethylformamide; in this regard zein resembles water soluble proteins such as insulin, ribonuclease, and lysozyme. On the basis of osmotic pressure measurements made in both formamide and dimethylformamide, alpha zein has a number average moleular weight of 21000-24000 daltons and shows no tendency to aggregate or dissociate. Beta zein exists in an aggregated state (dimer and higher forms) in dimethylformamide. Formamide dissociates the beta zein dimer into monomer units but aggregation to higher species occurs with increasing protein concentration.

Electrophoretic characterisation of low molecular weight nuclear RNA from SV40-transformed 3T3 cells

The electrophoretic mobility of the low molecular weight nuclear RNAs of SV40-transformed 3T3 cells have been measured on polyacrylamide gels of different concentration, and in the presence of the denaturing solvent formamide. Within this class of RNA molecules, a difference in electrophoretic mobility properties of one species, relative to the others, was observed, suggesting that its conformation differs markedly from that of the other species.

Density, viscosity and electrical conductivity of LiCl and some uni-bivalent electrolytes in formamide solutions at 25°C

Density, viscosity and equivalent conductivity in formamide at 25°C are reported for LiCl, Mg(ClO 4) 2, CaCl 2, CaBr 2, Ca(NO 3) 2, ZnCl 2, ZnBr 2 and ZnI 2 salts. The linear dependence of the density of the investigated salts on the concentration is interpreted assuming that the structural configuration of the solvent formamide remains unchanged in the concentration range experienced. Viscosity and conductivity data have been treated following a proposal of Angell. A least-squares program used to linearise the lg Λ and the lg η functions against 1/( N 0 − N) gives N 0 values, the glass-transition concentration at 25°C, acceptably low and sufficiently close in most cases.

Esca applied to liquids III. ESCA phase shifts in pure and mixed organic solvents

The ESCA phase shifts between the liquid and vapour have been measured in the pure organic solvents formamide, ethylene glycol and benzyl alcohol. Diff

Investigations on the relationship between molecular structure and chromatographic parameters : VII. Partition of phenols in systems of the type cyclohexane + polar solvent—formamide

Relatonships between R M values and the concentration of polar solvents in the mobile phase were determined for a group of halogenophenols, xylenols and several other derivatives of phenol. Three alcohols, olcic acid and chloroform were used as the polar component (S). It was found that alcohols, in spite of their auto-association, have high extration strengths relative to phenols. 1:1 solvation complexes being easily formed. Hindered solvation due to internal hydrogen bonding or steric shielding of the hydroxyl group resulted in less steep R M versus log % S lines.