Kamlet scale

Kamlet scale 458 kinetics, lithium alloys 366 ff kinks, lithium deposition 345 Kroger-Vink notation 529... 

The basic premise of Kamlet and Taft is that attractive solute—solvent interactions can be represented as a linear combination of a nonspecific dipolarity/polarizability effect and a specific H-bond formation effect, this latter being divisible into solute H-bond donor (HBD)-solvent H-bond acceptor (HB A) interactions and the converse possibility. To establish the dipolarity/polarizability scale, a solvent set was chosen with neither HBD nor HBA properties, and the spectral shifts of numerous solvatochromic dyes in these solvents were measured. These shifts, Av, were related to a dipolarity/polarizability parameter ir by Av = stt. The quantity ir was... 

The 7t scale of solvents (Kamlet-Taft scale) is intended to represent the solute-solvent interactions in the absence of strong forces such as hydrogen-bonding or dipole-dipole interactions. It is based on the n to n absorption of a series of seven solutes (six uitroaromatics, such as 4-uitroanisole, A, A -diethyl-3-nitroaniline, 1-ethyl-4-uitrobeuzeue, etc., aud 4-dimethylamiuobenzophenone) [51-53]. 

More advanced scale was proposed by Kamlet and Taft [52], This phenomenological approach is very universal as may be successfully applied to the positions and intensities of maximal absorption in IR, NMR (nuclear magnetic resonance), ESR (electron spin resonance), and UV-VS absorption and fluorescence spectra, and to many other physical or chemical parameters (reaction rates, equilibrium constant, etc.). The scale is quite simple and may be presented as ... 

Kamlet MJ, Abboud J-L, Taft R (1977) The solvatochromic comparison method. 6. The it scale of solvent polarities. JACS 99 6027-6038... 

Kamlet, M. J., A. Solomonovici, and R. W. Taft. 1979. Linear Solvation Energy Relationships. 5. Correlations between Infrared Ar Values and the (3 Scale of Hydrogen Bond Acceptor Basicities. J. Am. Chem. Soc. 101, 3734. 

Tab. 7.1. Parameters of the n scale of polarity (data from Kamlet et al., 1983)...

From a practical viewpoint, Ej values are quickly and easily obtained, giving a very useful and convenient scale. However, a general polarity scale based on a single probe molecule has its limitations because a single compound cannot experience the diversity of interactions that the whole range of solvents can offer. The Kamlet-Taft parameters a, /3 and n tackle this problem by using a series of seven dyes to produce a scale for specific and nonspecific polarity of liquids [23], Whilst it undoubtedly gives a more detailed description of the solvents properties,... 

Kamlet MJ, Taft RW (1976) The solvatochromic comparison method. 1. The /6-scale of solvent hydrogen-bond acceptor (HBA) basicities. J Am Chem Soc 98 377-383. 

Palm s group has continued to develop statistical procedures for treating solvent effects. In a previous paper, a set of nine basic solvent parameter scales was proposed. Six of them were then purifled via subtraction of contributions dependent on other scales. This set of solvent parameters has now been applied to an extended compilation of experimental data for solvent effects on individual processes. Overall, the new procedure gives a signiflcantly better flt than the well-known equations of Kamlet, Abboud, and Taft, or Koppel and Palm. 

Baker, S.N., Baker, G.A., Bright, F.V., Temperature-dependent microscopic solvent properties of dry and wet l-butyl-3-methylimidazolium hexafluo-rophosphate Correlation with ET(30) and Kamlet-Taft polarity scales. Green Chem., 4,165-169, 2002. 

For reviews, sec Abraham Doherty Kamlet Taft Chem. Br. 1986, 551-554 Kamlet Abboud Taft Prog. Phys. Org. Chem. 1981,13, 485-630. For a comprehensive table and a and p values, see Kamlet Abboud Abraham Taft J. Org. Chem. 1983, 48, 2877. For a criticism of the p scale, see Laurence Nicolet Helbert J. Chem. Soc., Perkin Trans. 2 1986, 1081. See also Nicolet Laurence Lugon J. Chem. Soc., Perkin Trans. 2 1987, 483 Abboud Roussel Gcntric Sraidi Lauransan Guihgncuf Kamlet Taft./. Org. Chem. 1988,53, 1545 Abraham Grcllier Prior Morris Taylor J. Chem. Soc., Perkin Trans. 2 1990, 521. 

For reviews of solvent polarity scales, see Abraham Grellier Abboud Doherty Taft Can. J. Chem. 1988,66. 2673-2686 Kamlet Abboud Taft Prog. Phys. Org. Chem. 1981,13,485-630 Shorter Correlation Analysis of Organic Reactivity Wiley New York, 1982, pp. 127-172 Reichardt, Ref. 386 Reichardt Dimroth, Ref. 386 Abraham Prog. Phys. Org. Chem. 1974, II, I -87 Koppel Palm, in Chapman Shorter Advances in Linear Free Energy Relationships, Plenum New York, 1972, pp. 203 280 Ref. 384. See also Chastrette Carrclto Tetrahedron 1962,38, 1615 Chastrette Rajzmann Chanon Purcell J. Am. Chem. Soc. 1965,107, 1. 

The method of linear solvation energy (LSER), based on the Kamlet-Taft multiparameter scale (10) has been successfully exploited to study retention in LC. The LSER approach, when applied to phase-transfer processes, correlates a general solute property (SP), such as logarithmic capacity factor, with parameters of the solute and both the mobile and stationary phases ... 

Steady-State Solvatochromism. The majority of the reports on supercritical fluid solvation have used steady-state solvatochromic absorbance measurements (21-28). The original aim of these experiments was to determine the solvating power of supercritical fluids for chromatography and extraction (SFC and SFE) (26,28). To quantify solvent strength, researchers (21-28) adopted the Kamlet-Taft x solvent polarity scale (50-55). This scale best correlates solvatochromic effects on a- x and x- x electronic absorption transitions. 

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 ... 

It was later shown by Laurence and coworkers that there are significant systematic differences between P values of solvents obtained with indicators with an oxygen donor atom and those with a nitrogen donor atom (Nicolet and Laurence 1986). These authors recommended the use of a single indicator, preferably 4-nitrophenol relative to 4-nitroanisole or else 4-nitroaniline relative to 4-nitro-N,N-di/rae%>/aniline (rather than 4-nitro-N,N-die// y/aniline used by Kamlet and Taft 1976), to establish a basicity scale. The main point of difference is with respect to solvents that do not have an oxygen donor atom, such as amines, pyridines, and sulfides. In order to save the P scale, Kamlet and Taft proposed a family-dependent covalency parameter, equal to -0.20 for P=0 bases, 0.00 for C=0, S=0, and N=0 bases, 0.20 for -O-bases, 0.60 for pyridines, and 1.00 for amines, for use in linear free energy relationships (Kamlet etal. 1985). 

The DN and P electron pair donicity scales are closely related to each other, as is to be expected. The correlation expression, established for 25 solvents for which both measures were known at the time, was DN = -0.9 + 39.18P (Kamlet et al. 1985). A correlation involving many more solvents has since been established ... 

The correlation between the Gutmann ZW/kcal mo"1 scale and the Taft and Kamlet (3 Lewis basicity scales, Eq. (4. 13)... 

Another property that characterizes solvents is their softness, in terms of the HSAB concept (Pearson 1963), according to which the interactions of soft solvents are strongest with soft solutes, of hard solvents with hard solutes, but are weaker for hard solvents with soft solutes and vice versa. The applicability of the softness property takes into account that it is superimposed on the more general electron pair donation property discussed above. In fact, it can replace (Marcus 1987) the notion of the family dependence of the P scale, expressed by the , parameter (Kamlet etal. 1985). A few quantitative scales have been... 

Of the existing solvent scales, the Kamlet and Taft n scale ( D appears appropriate for use with supercritical fluid solvents. The basis of the Kamlet and Taft scale is the effect of solvent polarity and polarizability on the energy of the n - it electronic transition of a solute probe molecule. Solvent molecules in proximity to a solute (the cybotatic region) differentially affect the electronic energy levels of solutes (the solvatochromic effect)... 

Since its introduction the Kamlet-Taft it scale has been applied to a large number of diverse liquid solvents ( 5). Several studies have shown that the it solvent scale is consistent with other popular measures of solvent strength (6J. It has also been shown that there are good correlations between the empirical measurements of the Kamlet and Taft scale and several theoretical models of solvent behavior (J). Use of the solutes chosen by Kamlet and... 

The Kamlet-Taft u polarity/polarizability scale is based on a linear solvation energy relationship between the n it transition energy of the solute and the solvent polarity ( 1). The Onsager reaction field theory (11) is applicable to this type of relationship for nonpolar solvents, and successful correlations have previously been demonstrated using conventional liquid solvents ( 7 ). The Onsager theory attempts to describe the interactions between a polar solute molecule and the polarizable solvent in the cybotatic region. The theory predicts that the stabilization of the solute should be proportional to the polarizability of the solvent, which can be estimated from the index of refraction. Since carbon dioxide is a nonpolar fluid it would be expected that a linear relationship... 

The standard molar Gibbs energy of solvation can also be derived from pure component data using spectroscopic information for determining solvatochromic parameters in respect of activity, basicity, polarity, etc. There exists a number of linear solvatochromic scales, the most widely used of which is the linear solvation energy relationship (LSER) devised by Kamlet and Taft [37, 38]. The Nernst distribution of solute i according to Kamlet is ... 

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