Bunnett-Olsen relationship

However, there are two important points in favor of the Bunnett-Olsen relationship. First, its range of validity extends down to dilute acid concentrations where the Yates treatment fails. Second, by expressing eqn (10) in terms of activity coefficients we may obtain... 

Equation (12) is a linear free-energy relationship, since activity coefficients/can be represented as AG° values. The reason for defining the slope parameter as in equation (12) (subscript e for equilibrium) is that a little rearranging of equations (11) and (12) leads to the easy-to-use Bunnett-Olsen equation for equilibria, equation (13) 30... 

TABLE 10. Analysis of rate data for hydrolysis of A-i-butylbenzaldoxime and 2-i-butyl-3-phenyloxaziridine at 24.2 C by use of Bunnett linear free-energy relationships... 

We have approached the problem of the relationship between protonation, solvation, and acidity functions. First we have discussed the present status of the determination of p and acidity functions for individual bases in terms of the Bunnett-Olsen equation. 

Reactivities of Side-chains of Monocyclic Thiophens.—The protonation of various furan- and thiophen-carboxamides in aqueous sulphur acid solution has been investigated by u.v. spectroscopy. The values of pKbh that were calculated using the acidity function and the Bunnett-Olsen linear free-energy relationship indicate the lower basicity of furan- and thiophen-2-carboxamides with respect to that of benzamides and of the 3-derivatives. The kinetics of isomerization of cw-l-(2-thienyl)-2-phenylacrylonitrile, as well as of its 2-furyl and 2-selenienyl analogues, have been studied in a solution of decahydronaph-thalene, with methanesulphonic acid and potassium t-butoxide as catalysts, and the mechanism has been discussed. ... 

Benoit, 1974) has enabled them to use the linear free energy relationship (BO) approach of Bunnett and Olsen (1966), and the (MCP) modification by Marziano, Cimino and Passerini (1973), to evaluate pKa (see also Levi et al., 1974). Not surprisingly, it is found that those compounds whose ionization is closely governed by an acidity function give similar p/ifa values by the BO, MCP and AF procedures. Appreciable differences result, however, for other compounds such as carbon acids, and the differences have been attributed to an incorrect anchoring of the AF scale for these acids. The chosen anchor, 9-phenylfluorene, had been assigned a pATa value of 18-59 (Bowden and Stewart, 1965). However the BO and MCP methods give a value close to 20 (Table 6). 

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