Showing papers on "Solvent effects published in 1970"
70 citations
TL;DR: In this article, solvent effects on the visible absorption (charge transfer) spectra of bis-(2,2'-bipyridyl)biscyanoiron(II), bis-(1,10-phenanthroline), and ligand-substituted derivatives are correlated with solvent E T parameters.
65 citations
TL;DR: In this article, the solvent effect on the activation volumes and energies at 35°C was investigated for the isoprene+maleic anhydride reaction in various solvents at pressures up to 1400 atm.
Abstract: The kinetics of the isoprene+maleic anhydride reaction have been studied in various solvents at pressures up to 1400 atm. The solvent effect on the activation volumes and energies at 35°C are reported. It is shown how the solvent effect on activation volumes is useful both for mechanistic interpretation as well as for determination of the dipole moment of the transition state.
54 citations
TL;DR: The ultraviolet absorption spectra of the mono-salicylideneimines of ethylamine, ethanolamine, and n-butylamine were examined in various solvents: water, absolute ethanol, dioxan, and cyclohexane as discussed by the authors.
Abstract: The ultraviolet absorption spectra of the mono-salicylideneimines of ethylamine, ethanolamine, and n-butylamine and of the bis-salicylideneimines of ethylenediamine, trimethylenediamine, and 1,3-diaminopropan-2-ol have been separately examined in various solvents: water, absolute ethanol, dioxan, and cyclohexane. A comparison of these spectra with those of the N-methylimines of m- and p-hydroxy-benzaldehydes in similar solvents indicates that the o- and p-hydroxybenzylideneimines exist mainly as the dipolar keto amines in very polar, hydrogen-bonding solvents whereas the m-isomers exist mainly as the enol imine tautomeric form in all solvents.
52 citations
48 citations
TL;DR: Barriers to nitrogen inversion have been studied in a number of 5-membered cyclic amines by variable temperature NMR spectroscopy as mentioned in this paper, where the substituent effects observed in these compounds are compared with those obtained in aziridine derivatives.
45 citations
45 citations
TL;DR: In this paper, the average distance of the bonding electrons in the chloroform C-H bond as the result of intermolecular association was measured in a variety of solvents.
Abstract: The ^(13)C chemical shift of chloroform has been measured in a variety of solvents Relative to dilute solution in cyclohexane, all of the solvents studied resulted in downfield shifts which, with the exceptions of benzene and acetonitrile, correlate linearly (r = 0982) with the changes in proton shifts in the same solvents The results, taken with the variation of the ^(13)C-H coupling constant with solvent, suggest that the solvent effects arise from
changes in the average distance of the bonding electrons in the chloroform C-H bond as the result of intermolecular association Contributions from the anisotropy of benzene and acetonitrile indicate that measurements of the chemical shift of more than one nucleus in the same molecule may allow detection and estimation of neighbor anisotropy contributions to chemical shifts
43 citations
TL;DR: In this paper, the authors compared the sensitivities of these charge-transfer bands to solvent variation for these systems and for Fe(LL) 2 (CN) 2, where LL = bipy, ophen, or one of their substituted derivatives, and M(bipy)(CO) 4, where M = Mo or W.
42 citations
41 citations
TL;DR: In this article, the rate enhancing effects of aromatic solvents (1-fluoro, 1-chloro-, 1-bromonaphthalene and toluene) on the photo-and thermal sensitized polymerization of methyl methacrylate by azoinitiators at 25° and 60° respectively were investigated by measuring k p, k r and R l by means of rate, molecular weight and sector experiments.
TL;DR: In this article, the dependence of the g factor of p-benzosemiquinone and its tetrahalogenated derivatives on the solvent composition has been studied in the dimethyl sulfoxide-water system.
Abstract: The dependence of the g factors of p-benzosemiquinone and its tetrahalogenated derivatives on the solvent composition has been studied in the dimethyl sulfoxide-water system. When the water content of the solvent increases, the g factor of p-benzosemiquinone decreases, that of tetrachloro-p-benzosemiquinone scarcely changes, and the g factors of tetrabromo- and tetraiodo-p-benzosemiquinones increase. These phenomena are interpreted qualitatively by assuming that the water molecule solvates to the carbonyl oxygen atom of semiquinones and by using Stoned equation for the g factor of the polyatomic radical. The dependence of the g factor of p-benzosemiquinone on the solvent composition is quantitatively studied by means of the theory of solvent effects proposed by Gendell, Freed and Fraenkel and by using the 2-site model of Stone and Maki and also the 4-site model. The former model assumes that one carbonyl oxygen atom has one site occupied by a solvent molecule, thus resulting in a dominant g shift. In the ...
TL;DR: In this article, the catalytic properties of chlorotris(triphenylphosphine)rhodium(I) and rhodium (III) chloride for the oxidation of olefins have been studied.
Abstract: Catalytic activities of chlorotris(triphenylphosphine)rhodium(I) and rhodium(III) chloride for the oxidation of olefins have been studied. It has been found that the complex and RhCl3 can cause catalytically the oxidation of aliphatic olefins such as styrene, α-methylstyrene or β-methylstyrene to produce carbonyl compounds under oxygen atmosphere. A remarkable solvent effect was observed in the reaction.
TL;DR: In this paper, the additivity of substituent effects on the aromatic and methyl proton chemical shifts is evaluated in detail in order to establish the reliability of the predicted chemical shifts.
TL;DR: The stereochemistry of 6-membered ring lactones in some naturally occurring steroids has been studied in this article, where it was shown that one of these lactones exists in a half chair conformation, whereas three other lactones (Vb, VII and VIII) are in ahalf boat conformation.
TL;DR: Optically active alpha-amino acids synthesis from esters of alpha-keto acids by hydrogenolytic asymmetric transamination as mentioned in this paper was proposed to synthesize alpha amino acids.
Abstract: Optically active alpha-amino acids synthesis from esters of alpha-keto acids by hydrogenolytic asymmetric transamination
TL;DR: In this article, the effect of solvent on the rate of protonation of the biphenyl radical anion by an alcohol: C12H10−−+ROH=C12H11−+RO− was studied for a number of mixed solvent systems.
Abstract: Absolute rate constants were determined, by the pulse radiolysis technique, for the electron transfer reaction from an aromatic radical anion to a different neutral aromatic molecule: A1·−+A2=A1+A2·− for a number of aromatic molecule pairs in ethanol, in ethylenediamine, and in diethylamine. The dependence of these rate constants upon the standard free energy for reaction of the pair and upon the dielectric properties of the solvent, as predicted by the theory of Marcus for electron transfer reactions, is found to support this theory, at least semiquantitatively, over a limited range. The effect of solvent on the rate of protonation of the biphenyl radical anion by an alcohol: C12H10·−+ROH=C12H11·+RO− was studied for a number of mixed solvent systems, namely, ethanol–ethylenediamine, ethanol–cyclohexane, ethanol–triethylamine, ethanol–diethylamine, ethylene glycol–ethylenediamine, and ethylene glycol–triethylamine. In the alcohol–amine systems the first order rate constant for the protonation reaction was...
TL;DR: In this paper, 15 N-enriched aniline, methylamine, N -methylacetamide, trimethylamine and quinoline were measured by heteronuclear double resonance.
TL;DR: In this paper, the effect of solvent on the stereochemical course of deuteration of benzyl methyl sulfoxide has been studied by two methods, and the relative rates of exchange of the diastereotopic methylene protons were found to vary from 14:1 (D2O/NaOD) to 0.5:1(tbutanol-OD/NaO-t-butyl).
Abstract: The effect of solvent on the stereochemical course of deuteration of benzyl methyl sulfoxide has been studied by two methods. In the first, the relative rates of exchange of the diastereotopic methylene protons were found to vary from 14:1 (D2O/NaOD) to 0.5:1 (t-butanol-OD/NaO-t-butyl). Experiments on quenching α-lithiobenzyl methyl sulfoxide with D2O gave the same diastereomers in ratios ranging from 1.7:1 (DMSO) to 0.065:1 (THF). The significance of these findings in relation to previous work on conformational stabilities of α-sulfinyl carbanions is discussed.
TL;DR: In this article, the non-Newtonian viscosity of concentrated solutions of a styrene-butadiene-styrene, SBS, block copolymer was measured with a novel capillary viscometer.
Abstract: The non-Newtonian viscosity of concentrated solutions of a styrene-butadiene-styrene, SBS, block copolymer was measured with a novel capillary viscometer. Polymer concentrations ranged from 0.165 to 0.306 g/cc. Apparent shear rates ranged from 1 to 105 sec−1. Five different solvents were employed. All of the flow curves can be reduced to a single master curve with the same shape exhibited by monodisperse polystyrenes and the Graessley theory. The shift factor for the shear rate axis, τ0, approximately parallels the Rouse relaxation time, τR, but shows a residual concentration and solvent dependence not predicted by the Rouse form. For different solvents at the same concentration, better solvents show a minimum relative zero shear viscosity, η0/ηs, and a maximum ratio τR/τ0. It is concluded that all solvent effects are not adequately incorporated into the zero shear viscosity for the purposes of constructing master plots; however, the shape of the master plot is not affected by the solvent or the polymer block structure.
TL;DR: In this article, the spectral intensity functions describing the dipolar interaction are derived from the translational diffusion of individual molecules, and a certain solvation effect has to be taken into account, in which strong solvation occurs in solutions of hydroxyl containing solvents with nitroxide radicals.
Abstract: Abstract Dynamic proton polarization in several free radical solutions has been studied systematically with different radicals at five widely separated magnetic field strengths and at various temperatures. Normally, in organic solutions the dynamic enhancements of the solvent proton resonances decay with increasing field and decreasing temperature. Scalar proton-electron coupling has only been observed in exceptional cases. The spectral intensity functions describing the experimental behaviour are derived from the dipolar interaction whose time dependence is in the first place due to translational diffusion of individual molecules. In addition, a certain solvation effect has to be taken into account. Strong solvation occurs in solutions of hydroxyl containing solvents with nitroxide radicals. In this case, the dynamic proton polarization appears to be quite different. As an example, solutions of tetramethyl piperidineoxyl in acetic acid have been examined in more detail. The results are explained in terms of hydrogen bridged solvates. The important motional mechanism that modulates the proton-electron interaction switches from “translation” to “rotation”, and electron spin density is temporarily transferred to the solvent molecule.
TL;DR: In this article, the equimolar reaction of 1,2-dichloroethane with sodium N,N-dimethyldithiocarbamate was studied in various solvents.
Abstract: The equimolar reaction of 1,2-dichloroethane with sodium N,N-dimethyldithiocarbamate was studied in various solvents. As major products, ethylene bis(N,N-dimethyldithiocarbamate) and 2-dimethylamino-l,3-dithiolanylium salt (the perchlorate or the tetraphenylborate) were obtained in yields, largely varying with the solvent used. On the basis of the solvent effect on the product ratio, and kinetic experiments it has been verified that neighboring-group participation of the N,N-dimethyldithiocarbamate function would be involved through the intermediacy of the isolated anchimeric carbonium ion, and that such participation is more predominant in nonpolar aprotic solvents such as dioxane and tetrahydrofuran. The mechanism of the reaction between 2-dimethylamino-l,3-dithiolanylium ion and the dithiocarbamate anion was established.
TL;DR: In this paper, the PMR spectrum of LiAl(CH 3 ) 4 has been investigated in a series of different solvents as a function of concentrations and temperature, and it has been shown that in 1,2-dimethoxyethane (DME) the compound is highly dissociated while in non-polar solvent it is sparingly soluble and strongly associated.
TL;DR: In this article, a theoretical expression for the oscillator strength of an electronic transition in a solute molecule immersed in an isotropic dielectric continuum of solvent is presented.
Abstract: A theoretical expression has been presented for an oscillator strength of an electronic transition in a solute molecule immersed in an isotropic dielectric continuum of solvent. It is assumed that a charged particle in the solute is subjected to a force due to a cavity field. The approximate expression derived on the basis of a quantum-mechanical perturbation theory has been successfully tested for nitrobenzene and acetone.
TL;DR: In this paper, the acceptor ability of halide ions with CCl4 has been investigated in CH2Cl2 and CH3CN solvents, with particular reference to the role of hydrogen bonding.