The solvatochromic comparison method. 2. The .alpha.-scale of solvent hydrogen-bond donor (HBD) acidities

Abstract

28869.5 ml(20-50-fold excess) of alcohol solution and thermostating for the period of time required for the disappearance of the yellow color of Cr(V1). Sodium hydroxide (100 ml, 2.5 M) was then added with cooling to the mixture to neutralize the acetic acid. Completeness of neutralization was monitored with pH paper. The resulting aqueous solution was twice extracted with 100 ml of ether, and the combined ether extracts were washed with water and dried (MgS04) and evaporated to a volume of ca. 0.5 ml. The mixture was then analyzed on a Hewlett-Packard Model 700 gas chromatograph equipped with dual flame ionization detectors. In each case, only the alcohol starting material and normal oxidation product were detected.Determination of Activation Parameters. Once the rate constants at various temperatures had been determined, Arrhenius plots of the natural logarithm of the rate constant against the reciprocal of the absolute temperature were made. To aid in the accurate plotting of these data and their linear regression analysis, the University of Delaware Burroughs B-6700 computer was utilized. The appropriate program was written by Dr. John J. Stanulonis of these laboratories and made available to us. The program permitted the determination of the least-squares slope of the plot and its intercept, as well as statistical information which indicated the reliability of the data. The statistical equations were those suggested by B a~e r .~~ From the slope of the Arrhenius plot, the energy of activation may be determined, using the relationshipPlotting In k vs. Am. Chem. Soc., 95,5242 (1973).A most recent review is given in H. Taube, A&. "rg. Chem. Radiochem., 1, l(1959).See R. P. Bell. Chem. Soc. Rev., 3,513 (1974). for a recent general review of this subject: see also, J. R. Hulett, 0. Rev., Chem. Abstract: The solvatochromic comparison method is used to evaluate hydrogen-bonding contributions in HBD (hydrogen-bond donor) solvents to several commonly used dye indicator solvent polarity scales (Dimroth's E~o , Brooker's XR. Kosower's Z ) . Hydrogen-bonding effects on other spectral properties, equilibria, and reaction rates are determined, and the results are used to construct an a-scale of solvent HBD acidities.X Y Z = X Y Z o + solvent polarity-polarizability effect Journal of the American Chemical Society / 98:lO / M a y 12, 1976

QSPR Modeling using Catalan Solvent and Solute Parameters

“…Examples of such solubility-related parameters include thermodynamic solubility parameter of Hildebrand, 1 and solvatochromic parameters. [2][3][4][5][6][7][8] A set of solvatochromic parameters was originally derived from spectroscopic methods of investigating the intermolecular interactions by Abraham in 1970-1980. [2][3][4][5] The parameters included solvent polarity/polarizability scale, solvent basicity scale, and solvent acidity scale, which were then used in QSPR models to estimate properties and activities of solvents or solutes in the solutions.…”

“…[2][3][4][5][6][7][8] A set of solvatochromic parameters was originally derived from spectroscopic methods of investigating the intermolecular interactions by Abraham in 1970-1980. [2][3][4][5] The parameters included solvent polarity/polarizability scale, solvent basicity scale, and solvent acidity scale, which were then used in QSPR models to estimate properties and activities of solvents or solutes in the solutions. [2][3][4][5] The parameter set was later extended to the corresponding solute descriptors of hydrogen-bonding acidity (A) and basicity (B) scales, and polarity/polarizability (S) scale.…”

“…7 Catalan parameters consist of solvent polarity/ polarizability scale (SPP), solvent basicity scale (SB defined as cb in this work), and solvent acidity scale (SA defined as ca in this work), 8,[20][21][22][23] which recently SPP parameter split into two separate scales: solvent dipolarity (SdP defined as cd in this work) and solvent polarizability (SP defined as cp in this work). 7 The approach for measuring these parameters is similar to those of Kamlet and Taft,2,3 where a probe with specific interactions with solvent has been used and variances in spectroscopy data have been recorded and applied for the definition of the solvent scales. [2][3][4]8,[20][21][22][23] In formulating the independent solvent scales, the choice of an appropriate probe for the experimental determination of the scales is the major challenge.…”

“…2-5 The parameters included solvent polarity/polarizability scale, solvent basicity scale, and solvent acidity scale, which were then used in QSPR models to estimate properties and activities of solvents or solutes in the solutions. [2][3][4][5] The parameter set was later extended to the corresponding solute descriptors of hydrogen-bonding acidity (A) and basicity (B) scales, and polarity/polarizability (S) scale. 9,10 In addition to these parameters, the general solvation equation proposed by Abraham and co-workers 9,10 (equation 1) also includes excess molar refraction (E) and the one percent of McGowan molar volume (V).…”

“…7 The approach for measuring these parameters is similar to those of Kamlet and Taft, 2,3 where a probe with specific interactions with solvent has been used and variances in spectroscopy data have been recorded and applied for the definition of the solvent scales. [2][3][4]8,[20][21][22][23] In formulating the independent solvent scales, the choice of an appropriate probe for the experimental determination of the scales is the major challenge. The selected probe should measure the effect of a single solvent property, for example, hydrogen-bonding basicity, without the interference of any other solvent effects.…”