Empirical Solvent Polarity Parameter Research Articles

Intermolecular interactions in water + acetonitrile mixtures : Evidence from the composition variation of solvent polarity parameters

The dependence on composition of the polarity of H2O+MeCN mixtures has been determined from measurements of the empirical solvent polarity parameter ET. ET has been found to vary with composition in a similar fashion to that which has been reported previously for most other H2O+non-electrolyte mixtures for which ET data are available. The variation of ET with composition is interpreted in terms of the Naberukhin-Rogov structural model for H2O+nonelectrolyte mixtures.

Empirical Parameters of Solvent Polarity as Linear Free‐Energy Relationships

AbstractAlthough the effect of solvent on the rate and the position of equilibrium of chemical reactions has been known since the last century, there are still no reliable and exact methods for a quantitative description and prediction of such solvent effects. Empirical parameters of solvent polarity are of great value in this respect and can be derived with the aid of the principle of “linear relationships between free energies” (LFE relationships). The present article deals with the possibilities of establishing reaction and absorption series using solvent‐dependent standard reactions or standard absorptions of organic compounds. Particular attention is merited by the summary of the 24 most important empirical parameters of solvent polarity and the table of ET(30) values for 151 solvents. In addition to examples of the application of these values, attempts to improve the LFE correlations of singular empirical parameters of solvent polarity with the aid of multiparametric equations are described.

Solvent effects in the reaction of 2‐thiophenesulfonyl chloride with aniline

AbstractThe second order rate constants k2 and the activation parameters for the reaction of 2‐thiophenesulfonyl chloride with aniline together with solution enthalpies of the reactants have been measured in methanol, ethanol, 2‐propanol, acetonitrile and acetone. The reaction rates are slower in dipolar aprotic solvents than in protic ones due to a remarkable activation negative entropy. The rate constants k2 are correlated with empirical solvent polarity parameters. The data seem in accord with a SAN reaction mechanism.

The Effect of Mutual Solubility on the Distribution of the Methylene Group between Different Organic Solvents and Water

Abstract The contribution of the methylene group to the distribution coefficient (Δ log KD /CH2) has been obtained for 38 different solvents. For nonpolar solvents Δ log KD /CH2 is in the range 0.60 to 0.64, whereas for polar solvents it is in the range 0.33 to 0.58. Attempts have been made to correlate group values with solvent polarity, and it is found that the solubility of water in the organic solvent phase has a profound effect. Equations are derived from the three-suffix Margules equation for a ternary system that relate Δ log KD /CH2 to mole fraction solubility of water. The agreement between theoretical and experimental values is good for the case of alcohol solvents. Correlations with the empirical solvent polarity parameter of Reichardt are also examined.

Determination of empirical parameters of solvent polarity E T in binary mixtures by solvatochromic pyridinium-N-phenol betaine dyes

Empirical parameters of solvent polarity E T of some pure solvents and their binary mixtures (especially with CCl4 and CHCl3) were determined spectrophotometrically using solvatochromic pyridinium-N-phendl betaine dyes. Calibration curves are given for 16 binary solvent mixtures. The obtained E T values show that a synergetic polarity effect appears with the organic solvents containing C=O, P=O, and S=O groups in the mixture with chloroform. With these binary mixtures the increase of E T values results from the formation of 1∶1 complexes X=O... H-CCl3 by means of hydrogen bonding. Increasing number of methylene groups in the chain increases the synergism with these type of complexes.

Solvent Effects on Charge-transfer Fluorescence Bands

CHARGE-TRANSFER (CT) transitions in complexes with an ionic ground state, leading as they do to annihilation of the charge, are particularly sensitive to the polarity of the solvent. Such transitions have been used to derive the empirical solvent polarity parameters Z (ref. 1) and ET (ref. 2) which correlate well with the transition energies of other complexes with charged ground states3–5. Complexes in which the ground state is non-ionic show, on the other hand, little correlation between the energy of the charge-transfer transition and ET (or Z), because of the Franck–Condon restriction on reorganization of the solvent during the transition. The CT fluorescence transitions in such complexes should, however, correlate well with Z and ET provided that the lifetime of the excited state is sufficient to allow reorganization of the solvent. The energy of the CT fluorescence transition should thus decrease with an increase in solvent polarity, the reverse of the trend observed for the absorption process. Few complexes have been found to fluoresce in fluid solution6,7, and these only in a few solvents, mainly of very low polarity. The fluorescence band maxima measured in a range of solvents using a Baird-Atomic SF100 spectrofluorimeter for the complex hexamethylbenzene–tetrachlorophthalic anhydride are shown in Table 1, and Fig. 1 is a plot of the fluorescence band energy, ECT, against the solvent polarity parameter, ET. A good straight line with a slope close to unity (0.91) is obtained, showing that solvent stabilization of the excited state is very similar to that of the ground state in ionic complexes.