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Empirical acceptor number

Raman spectroscopy has up to now mainly been applied to elucidate conformational forms and associated conformational equilibria of the IL components. Yet other applications are appearing in these years. One example is the characterization of metal ions like Mn, Ni Y Cu Y and Zn + in coordinating solvent mixtures by means of titration Raman Spectroscopy [118]. Another issue is the study of solvation of probe molecules in ILs. In such a study [118], for example, acceptor numbers (AN) of ILs in diphenylcyclopro-penone (DPCP) were estimated by an empirical equation associated with a C=C / C=0 stretching mode Raman band of DPCP. According to the dependence of AN on cation and anion species, the Lewis acidity of ILs was considered to come mainly from the cation charge [119]. [Pg.346]

As outlined in Section 1.3, the solvent acidity and basicity have a significant influence on the reactions and equilibria in solutions. In particular, differences in reactions or equilibria among the solvents of higher permittivities are often caused by differences in solvent acidity and/or basicity. Because of the importance of solvent acidity and basicity, various empirical parameters have been proposed in order to express them quantitatively [1, 2]. Examples of the solvent acidity scales are Kosower s Z-values [8], Dimroth and Reichard s Er scale [1, 9], Mayer, Gutmann and Gergefs acceptor number (AN) [10, 11], and Taft and Kalmefs a parameter [12]. On the other hand, examples of the solvent basicity scales are Gut-... [Pg.16]

Acceptor number (or acceptivity), AN — is an empirical quantity for characterizing the electrophilic properties (-> Lewis acid-base theory) of a solvent A that expresses the solvent ability to accepting an electron pair of a donor atom from a solute molecule. AN is defined as the limiting value of the NMR shift, S, of the 31P atom in triethylphosphine oxide, Et3P=0, at infinite dilution in the solvent, relative to n-hexane, corrected for the diamagnetic susceptibility of the solvent, and normalized ... [Pg.1]

The Gutmaim s Acceptor Number (AN) was proposed [Gutmann, 1978] as a quantitative empirical parameter of solvent hydrogen bond acidity based on P-nmr shifts of thiethylphosphine oxide at infinite dilution, calculated as AN = -6 " 2.349. [Pg.267]

Extensive studies have been made of solvent effects on atom transfer reactions involving ions [12]. In the case of reaction (7.3.23), the rate constant decreases from 250M s in A-methylpyrrolidinone to 3 x 10 M s in methanol. This effect can be attributed to solvation of the anionic reactant Cl and the anionic transition state [12]. Since the reactant is monoatomic, its solvation is much more important. It increases significantly with solvent acidity leading to considerable stabilization of the reactants. As a result the potential energy barrier increases and the rate decreases with increase in solvent acidity. As shown in fig. 7.7, this leads to an approximate linear relationship between the logarithm of the rate constant and the solvent s acceptor number AN, an empirical measure of solvent acidity (see section 4.9). Most of the results were obtained in aprotic solvents which have lower values of AN. The three data points at higher values of AN are for protic solvents. [Pg.322]

Various attempts have been made to classify solvents, e.g. according to bulk and molecular properties empirical solvent parameter scales hydrogen-bonding ability and miscibility >. In table I solvents are divided into classes on the basis of their acid-base properties which can be used as a general chemical measure of their ability to interact with other species. Detailed information on these and other solvents, their symbols, fusion and boiling pointe and Gg), bulk properties (6,Ti, q), and currently-used correlation parameters DN (donor number), Ej-value, and AN (acceptor number) is given in Appendix A-1. [Pg.38]

Gutimnn s Acceptor Number (AN). Mayer, Gutmann, and Gerger (112) have used infinite dilution P-nmr shifts of triethylphosphine oxide (52) as the basis for what they describe as Acceptor Number (AN), a quantitative empirical parameter for the electrophilic properties of solvents (the conversion factor is —5"" = AN/2.349). For protic solvents AN is intended to serve as a measure of HBD acidity for nonprotic solvents it is seemingly intended as a measure of Lewis-type acidity. Compared with a values which range from 33.5 to 41.3 for the aliphatic alcohols, AN values of representative non-HBD solvents are THF, 8.0 ethyl acetate, 10.8 DMSO, 19.3. Thus, the latter solvents are... [Pg.597]

Although the success of the empirical solvent parameters has tended to downgrade the usefid-ness of the dielectric approach, there are correlations that have succeeded as exemphfied by Figure 13.1.1. It is commonly held that the empirical solvent parameters are superior to dielectric estimates because they are sensitive to short-range phenomena not captured in dielectric measurements. This statement may not be generahzed, however, since it depends strongly on the chemical reaction investigated and the choice of solvents. For instance, the rate of the Menschutkin reaction between tripropylamine and methyl iodide in select solvents correlates better with the log e function than with the solvent acceptor number. ... [Pg.742]

Theoretical and semiphenomenological approaches use the bulk properties or molecular quantities, dipole and quadrupole moments, polarizability, and so on, or mean force potentials in order to take these effects into account. Empirical methods take account of them with the help of empirical scales such as donor numbers, acceptor numbers, or correlation parameters. [Pg.80]

The first reference in Sec. 10.5.3 correlates the absorption bands of the first complex with the solvent Et parameter. The second reference reports an empirical linear correlation between (V1-V2) and aDN+PAN(V and V2) are the wave numbers of the two long wavelength bands of the complex and a and P are empirical constants related to the donor number DA and acceptor number AN of the solvent. The reference also correlates these numbers with the hyperfme splitting constant of V esr spectra. However, as Selbin (CAe ./fev.65(1965)153) pointed out, meaningful theoretical interpretations are complicated by [Pg.296]

Actually, many empirical parameters can be lumped into two broad classes, as judged from the rough interrelationships found between various scales. The one class is more concerned with cation (or positive dipole s end) solvation, with the most popular solvent basicity scales being the Gutmann DN, the Kamlet and Taft p, and the Koppel and Palm B. The other class is said to reflect anion (or negative dipole s end) solvation. This latter class includes the famous scales tt, a, Ej.(30), Z, and last but not least, the acceptor number AN. Summed up ... [Pg.755]

Mayer U, Gutmann V, Gerger W. The acceptor number—A quantitative empirical parameter for the electrophilic properties of solvents. Monatsh fur Chem. 1975 106 1235-1257. [Pg.257]

Using the empirical parameter of the solvent polarity Z based on the molar energy of the transition in E, in kilocalorie per mole (kcal/mol) for the CT band, the Ep values of sodium salt of l-methyl-4-[2-(4-hydroxyphenyl)ethenyl)]pyridinium] hydrogensquarate are shown in Table 6.3. These data illustrate the analogy between the Z values of the sodium salt of l-methyl-4-[2-(4-hydroxyphenyl)ethenyl)]pyridinium] hydrogensquarate with Ep(30), which is the empirical solvent polarity parameter, based on the intramolecular charge transfer absorption of a pyridinium-N-phenolate betaine dye. The Z values are practically equal in the solvents acetone, pyridine, and cyclohexane, which means that for a difference in the values of 8, solvent donor number (DN) and solvent acceptor number (AN) of 35.3, 33.1, and 18.9 (kcal/mol), the... [Pg.154]

The solvent triangle classification method of Snyder Is the most cosDBon approach to solvent characterization used by chromatographers (510,517). The solvent polarity index, P, and solvent selectivity factors, X), which characterize the relative importemce of orientation and proton donor/acceptor interactions to the total polarity, were based on Rohrscbneider s compilation of experimental gas-liquid distribution constants for a number of test solutes in 75 common, volatile solvents. Snyder chose the solutes nitromethane, ethanol and dloxane as probes for a solvent s capacity for orientation, proton acceptor and proton donor capacity, respectively. The influence of solute molecular size, solute/solvent dispersion interactions, and solute/solvent induction interactions as a result of solvent polarizability were subtracted from the experimental distribution constants first multiplying the experimental distribution constant by the solvent molar volume and thm referencing this quantity to the value calculated for a hypothetical n-alkane with a molar volume identical to the test solute. Each value was then corrected empirically to give a value of zero for the polar distribution constant of the test solutes for saturated hydrocarbon solvents. These residual, values were supposed to arise from inductive and... [Pg.749]

Brouwer and Krijnen (95JOC32), by ab initio and semi-empirical quantum chemical calculations of piperidine, N-methylpiperidine and a number of derivatives incorporating 7r-electron acceptors at the 4-position... [Pg.86]


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See also in sourсe #XX -- [ Pg.25 , Pg.26 , Pg.49 , Pg.80 , Pg.438 , Pg.439 , Pg.465 ]




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Acceptor number

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