Showing papers on "Solvent effects published in 1968"
134 citations
121 citations
TL;DR: In this article, the Onsager model of dielectrics is applied to the analysis of solvent shifts of absorption bands and correlations with various solvent properties, such as dipole moments and polarizabilities of excited states.
Abstract: Experimental observations about solvent shifts of absorption bands are reviewed, and correlations with various solvent properties are discussed. The theory is treated according to the Onsager model of dielectrics which shows how data like dipole moments and polarizabilities of excited states can be obtained from solvent-shift experiments. Shifts resulting from dispersion interaction and from specific solvent–solute interaction, in particular hydrogen bonding, are considered. Possible improvements in the theory of solvent shifts are briefly discussed.
112 citations
TL;DR: In this paper, a systematic investigation of the near UV and visible spectra of mono-substituted anthraquinones and the solvent effects on the longest wavelength π → π* absorption band of these compounds was performed.
104 citations
89 citations
TL;DR: In this paper, the authors reported the intensity and frequency data for the 2800 A transitions of 9 ketones and 5 nitroparaffins in the vapour and in 11 solvents.
78 citations
TL;DR: In this paper, the position and relative orientation of OMe groups in methoxyflavones can be inferred from benzene-induced solvent shifts of the OMe resonances, and the authors show that an OMe at C-5 suffers a drastic algebraic decrease in solvent shift upon the introduction of an ortho-OMe group at c-6.
68 citations
63 citations
TL;DR: In this article, the effect of metal to amine charge transfer bands of bipyridyl and phenanthroline-tetracarbonyl chromium (0), molybdenum (0) and tungsten (0).
Abstract: Absorption bands, especially metal to amine charge transfer bands of bipyridyl- and phenanthroline-tetracarbonyl chromium (0), molybdenum (0) and tungsten (0) are shifted in various solvents by less than 4500 cm−1. The shift is discussed in accordance with McRae’s equation, which was derived with the point-dipole approximation. The solvents can be classified into two groups, the alcohol and the ester group. When three constants corresponding to (1) the interaction between induced dipoles of the solute and of the solvent, (2) the interaction between permanent dipole of the solute and induced dipole of the solvent, and (3) the interaction between permanent dipoles of the solute and of the solvent, are duely chosen for the two groups of solvent individually, the experimental values are satisfactorily accounted for. Short range interactions, such as hydrogen bonding can be ignored.
59 citations
TL;DR: In this article, the mechanism of the Wolff-Kishner reduction is discussed in the light of accumulated information about the kinetics, thermodynamics, and solvent effects of the process.
Abstract: The mechanism of the Wolff-Kishner reaction is discussed in the light of accumulated information about the kinetics, thermodynamics, and solvent effects of the process. Wolff-Kishner reduction under normal conditions is thought to involve the trans hydrazone anion, which, in the rate-determining step, exhibits a more or less concerted proton capture at the carbanion terminal and undergoes a solvent-induced proton loss at the nitrogen terminal. The stereochemistry of the Wolff-Kishner reduction is believed to be affected by the presence of “ortho” substituents and by a change to a nonpolar, aprotic reaction medium. The mechanism elaborated for the Wolff-Kishner reduction is extended to the Wolff-Kishner elimination and isomerization reactions. Conformational analysis of the intermediates permits correlation of the competitive reduction and elimination processes with the structures of acyclic systems.
57 citations
TL;DR: In this paper, the intensities of polarized Raman bands of carbon tetrachloride, benzene, cyclohexane, carbon disulfide, chloroform, acetone, and acetonitrile have been measured in binary mixtures with a wide variety of solvents, at concentrations ranging from 20 to 80% in volume.
TL;DR: In this article, the effects of formaldehyde and hemiformal equilibria on the rates of the base-catalyzed and hydroxymethylations of phenol by aqueous formaldehyde have been treated quantitatively.
Abstract: The effects of formaldehyde and hemiformal equilibria on the rates of the base-catalyzed and hydroxymethylations of phenol by aqueous formaldehyde have been treated quantitatively. A kinetic model treating all seven simultaneous, parallel, consecutive, and competing reactions, as well as the equilibria, has been shown to apply to a wide variety of the conditions and to data from other works. Concentration-induced solvent effects on the rates and on the ortho/para-substitution patters have been studied. The temperature dependence of the rate constants, both for dilute systems and systems composed primarily of phenol and aqueous formaldehyde, has been determined.
TL;DR: 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 as discussed by the authors.
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.
TL;DR: In this paper, the authors studied the catalytic hydrogenation reaction of Schiff bases of alpha-keto acids with optically active alpha-alkylbenzylamine and showed that the reaction is similar to the one described in this paper.
Abstract: Solvent effect in catalytic hydrogenation reaction of Schiff bases of alpha-keto acids with optically active alpha-alkylbenzylamine
TL;DR: The analysis of substituent effects in the π-bonded benzenes showed that while for ortho and para positions, for the meta position this behaviour is inverted in the two series of compounds as mentioned in this paper.
TL;DR: In this article, the intramolecular hydrogen bond is disrupted by polar solvents and the acetamido group adopts a posi cation in the ortho position.
Abstract: In acetanilides bearing nitro, halogen, alkoxyl, or carboxyl substituents in the ortho position, the intramolecular hydrogen bond is disrupted by polar solvents and the acetamido group adopts a pos...
TL;DR: In this article, the occurence of an intramolecular charge transfer interaction has been confirmed by solvent effects and the change of π-base strength in a series of compounds, p-O2NC6H4(CH2)nNHAr, where Ar groups are phenyl, 2,4-dimethylphenyl, mesityl, panisyl, α-naphthyl, and β-nophthyl groups.
TL;DR: In this paper, the NaH-catalyzed Michael type condensations of (−)-menthyl chloropropionate with methyl methacrylate, conducted in media of varying dielectric constant, unequivocally showed the dependence of stereoselectivity of the reaction on solvent polarity.
TL;DR: In this paper, the P.M. spectra of thiophene-chromium-tricarbonyl and of the two monomethyl derivatives have been recorded both in chloroform-d 1 and acetone-d 6 solution.