Ionizing power, table

Table 4.11 lists the Y values for some alcohol-water mixtures and for some other solvents. The Y value reflects primarily the ionization power of the solvent. It is largest for polar... 

Table 8-12. The Solvent Ionizing Power Measure for Aqueous Mixed Solvents at 25°C...

Table 8-13. Solvent Ionizing Power (Yor,) and Nucleophilicity (Non) Based...

The quantity Y = log k - log k0 characterizes the ionizing power of the solvent (Grunwald and Winstein 1948). Here k0 is the rate constant at 25°C in the reference solvent, 80% v/v ethanol + 20% v/v water, and k is the rate constant in any other solvent studied. Representative values of Y are shown in Table 2.5 (Reichardt 1998 Grunwald and Winstein 1948 Abraham 1972, 1985 and Parker 1978). 

Table 8.4 lists some common organic solvents in order of decreasing ionizing power (or ability to stabilize ions). 

Consequently there appears to be a sound empirical basis for the use of the OTs scale of solvent ionizing power. Its use should be restricted to sulphonates, however, because of the differential effects of electrophilic solvation in acidic solvents (see Section 4). The importance of these effects can be seen by comparing the Y and Iqxs values for carboxylic acids (Table 5) it appears that, relative to 80% ethanol/water, a carboxylic acid ionizes a tosylate about ten times more rapidly than a chloride. 

The relative yields of cyclized products increase greatly with the decreasing nucleophilicity (2a-c, 3 and 4 of Table 3) and with the increasing ionizing power of the solvent. Cyclobutanone derivatives (32) are usually obtained in much greater amounts than cyclopropyl ketones (33) but, when mercuric ions are added, formation of 33 is overwhelming. The effect of R in 31 on the product distribution is illustrated in cases 3b, 4a, 5a, 6a, and 7. 

Sulfur dioxide is a r-electron-pair acceptor. The standard explanation for the strong ionizing power of SO2 is the formation of an EPD—EPA complex between the halide anion and the sulfur dioxide molecules [148], Table 2-11 summarizes some of the available data concerning the comparative efficiencies of various solvents in promoting the ionization of chloro-triphenylmethane [150],... 

Nuclear magnetic resonance investigations demonstrate (Table HI) the existence of an empirical relationship between the ionizing power of the EPD solvents and the coupling constants J(CH3- Sn) of the ionized substrate the coupling constants are increased by increasing donicitiy of the EPD. 

Ionizing Power of the Medium. The effect of an ionizing solvent upon the course of elimination reactions can be deduced by considering the distribution of electrical charge in the transition state of the different reactions (see p. 85). In Table 1 are summarized the conclusions... 

Table II. Yield (Percent) and Stereochemistry of Products of Solvolyses of Cyclohexen-4-yl Tosylate (III) in Solvents of Various Nucleophilicity and Ionizing Power...

Table I. Solvent Nucleophilicity (JV) and Ionizing Power (Y) Obtained by Transformation of A and B Parameters ferf-Butyl Chloride Based...

Table IV. Sensitivities of Nucleophilicity (s) and Sensitivity to Ionizing Power (m) Adamantyl Tosylate Based...

For comparative purposes, the solvolytic rate constants for I-VI at 25 °C in hexafluoroisopropyl alcohol (HFIP) are given in Table I, together with the m values, which measure the dependence of the rates on the solvent ionizing power parameter OTs by the equation log (k/k0) = raY0Ts (3, 6). 

Table I. Rate Dependence on Solvent Ionizing Power of Benzylic Sulfonates ArCR(CF3)OTs Relative to C6H5CH2OMs at 25 °C in HFIP...

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