Kamlet-Taft solvent parameter

Kamlet-Taft solvent parameters, 2, 123 Kanamycins episulfides... 

Equations containing a number of solvent parameters in linear or multiple linear regression and expressing the effect of the solvent on the rate of the reaction or the thermodynamic equilibrium constant. See Ej Values Kamlet-Taft Solvent Parameter Koppel-Palm Solvent Parameter Z Value... 

Kamlet-Taft solvent parameters Parameters of the Kamlet-Taft solvatochromic relationship that measure separately the hydrogen bond donor (a), hydrogen bond acceptor (P), and dipolarity/POLARiZABiLiTY (ji ) properties of solvents as contributing to overall solvent POLARITY. 

KAMLET-TaFT SOLVENT PARAMETER KOPPEL-PALM SOLVENT PARAMETER STABILITY CONSTANT Z-VALUE. 

GRUNWALD-WlNSTEIN EQUATION IONIZING POWER KAMLET-TAFT SOLVENT PARAMETERS Z-VALUE. 

GRUNWALD-WlNSTEIN EQUATION KAMLET-TAFT SOLVENT PARAMETERS KOPPEL-PALM SOLVENT PARAMETERS SOLVOPHOBICITY PARAMETER Z-VALUE. 

More recent solvatochromic studies [14-20] employ specialised dyes reflecting specific microscopic molecular interactions. For example, the Abboud-Kamlet-Taft solvent parameters [21-23] a, 3 and n give information on hydrogen bond donor and acceptor properties and the polarisability of a compound, respectively. For ionic liquids with [C4mim]-cations, the following order of [3- values was estab-... 

Figure 9.16 LSER correlation of initial rate constant with Kamlet-Taft solvent parameters. ...

Lu, J., Brown, J.S., Liotta, C.L. and Eckert, C.A., Polarity and hydrogen-bonding of ambient to near-critical water Kamlet-Taft solvent parameters, Chem. Commun., 2001, (7), 665-666. 

What seems to be happening is that, though the solvent does produce an effect on AG°, at the same time there is a change in the bond order of the transition state, rfi. According to Figure 9.2, this can be correlated with the Kamlet-Taft solvent parameter which is an empirical measure of the capacity of the solvent to coordinate via the donation of a pair of non-bonding electrons, i.e. the solvent acts as a Lewis base. 

The oxidation of meta- and para-substituted anilines with imidazolium fluorochro-mate (IFC)18 and nicotinium dichromate (NDC),19 in several organic solvents, in the presence of p-toluenesulfonic acid (TsOH) is first order in the oxidant and TsOH and is zero order with respect to substrate. A correlation of rate data in different solvents with Kamlet-Taft solvatochromic parameters suggests that the specific solute-solvent interactions play a major role in governing the reactivity, and the observed solvent effects have been explained on the basis of solute-solvent complexation. The oxidation rates with NDC exhibited negative reaction constants, while the oxidation with IFC did not correlate well with any linear free energy relationships. 

A solvatochromic scale, based on the ultraviolet-visible, rather than the infrared, spectral band of suitable probes is that based on the Kamlet -Taft P parameter. This is again an averaged quantity, for which the wavenumber shifts of several protic indicators relative to structurally similar but aprotic homomorphs are used (Kamlet et al. 1983 Kamlet and Taft 1976). It is assumed that the nonspecific effect of a solvent on the protic probe is the same as that on the aprotic one, and that it can be expressed in terms of the n parameter for the solvent, so that the donicity of the solvent, if it is a Lewis base, causes the difference between the responses of the two probes towards the solvent. The probes originally employed were 4-nitrophenol (vs 4-nitroanisole) and 4-nitroaniline (vs 4-nitroN,N-diethylaniline), but once a n scale is known, the need for the specific aprotic homomorph values no longer exists, since the general expression ... 

This interpretation is also supported by the results of a study correlating the observed diastereomeric excess with the Kamlet-Taft (3 parameter [29], a measure of the hydrogen-bond acceptor strength. A linear free energy relationship was found to exist between P and the diastereomeric excess for those solvents having a (hydrogen bond donor strength) = 0 [28],... 

A number of studies have attempted to characterize ionic liquids through their dielectric constant, and all have observed inconsistencies between the measured dielectric constant and the solvation properties of the liquid. Recent experiments making use of dielectric reflectance spectroscopy [214] indicate dielectric constants in the range of 10-15 for a series of imidazolium-based ILs, substantially lower than those for molecular solvents observed to possess comparable polarities as estimated by solvatochromism. Weingartner [215] has recently published a series of static dielectric constants obtained from dielectric reflectance spectroscopy, and compared them with those of common molecular liquids. The analysis includes comparison with the Kamlet-Taft ji parameter for the liquids from Eq. (11) we have prepared a plot of n versus dielectric constant in Fig. 6. The relationship between n and e for molecular liquids... 

One implication of this framework is that the electrostatic component of solute-solvent interactions should correlate strongly with the charge density of the liquid. This result is confirmed by study of the variation of the Kamlet-Taft n parameter with the number density of an ionic liquid. The result is shown in Fig. 7 (taken from [239]). This figure shows a clear relationship between it and the number density of the IL, where no such relationship exists in molecular liquids. It... 

Figure 7. The Kamlet—Taft n parameter vs. solvent number density. Select molecular solvents possess little or no capacity for hydrogen bonding, and their interactions are controlled by electrostatics. Ionic liquids are categorized based on whether they possess a cyclic cation or an alkylammonium cation. A wide range of anions are employed in both categories, and no attempt is made to restrict specific interactions. Taken from Ref. [239]...

A comprehensive research of a large number of benzofurazan nitro derivatives using UV spectroscopy and other physical-chemical methods has been carried out [777, 1006, 1007, 1106, 1107, 1229-1241], The frequencies of long-wave absorption bands of hydroxy- and aminosubstituted of nitrobenzofurazans greatly depend on the solvent nature [1106, 1107, 1230-1233, 1235, 1236], They are assigned to the bands of intramolecular charge transfer [1007, 1232], Correlation relationships between the wave number (v) and the Kamlet-Taft solvatochromic parameter (it ) are presented in the works cited ... 

INVESTIGATED SOLVENTS AND THEIR KAMLET-TAFT SOLVATOCHROMIC PARAMETERS (12,1. 124 ... 

FIGURE 1. Correlation of scales for some common EPD/HBA solvents with solvatochromic comparison probe pairs with the Kamlet-Taft /3kt parameters. Circles pair 8/7, squares pair 1/2, and triangles pair 17/18 (empty symbols for alkylamines), all normalized with 0.00 for cyclohexane and 1.00 for HMPA... 

FIGURE 9. Correlation of the fluorescence spectra of HPTA in pure solvents with the Kamlet-Taft solvent-polarity parameters ... 

FIGURE 20. The poor correlation found between the fluorescence maximum of IN and solvent polarity using Kamlet-Taft solvent-polarity parameters of 15 common solvents (from Reference 91)... 

One such methodology is the Kamlet-Taft Solvatochromic parameter approach. In this methodology, a solvent can be characterized by three parameters, tt, a measure of the polarity and polarizability of the fluid, a, the acidity or hydrogen bond donor capability and P, the hydrogen bond acceptor capability or basicity. Each of these parameters is determined from the shift in UV-visible absorbance of a series of select indicator species dissolved in the solvent. Rather than depending on the bulk properties of the fluid, as is the case with the cohesive energy approaches, the solvatochromic parameters are derived from the interactions between the indicator solute and the immediate solvent shell, in effect they are a measure of how a solute sees the solvent. In each case, the scale of values has been normalized to between 0.0 for cyclohexane... 

A subsequent multiple linear regression analysis [138] focused on the Kamlet-Taft solvatochromic parameters, employing transfer Gibbs energies and enthalpies AG°t and AH°r) for 26 solvents. Standard molar Gibbs energies of transfer for nine univalent and six divalent small cations correlated well with the Kamlet-Taft parameters via linear solvation energy relationships of the form... 

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