An examination of linear solvation energy relationships

Solvents have been parameterized by scales of dipolarity/polarizability π*, hydrogen-bond donor (HBD) strength α, and hydrogen-bond acceptor strength β. Linear dependence (LSER's) on these solvent parameters are used to correlate and predict a wide variety of solvent effects, as well as to provide an analysis in terms of knowledge and theoretical concepts of molecular structural effects. Some recent applications utilizing this approach are presented. Included are analyses of solvent effects on (a) the free energies of transfer of tetraalkylammonium halide ion pairs and dissociated ions, (b) rates of nucleophilic substitution reactions, (c) the contrast in solvent effects of water (HBD) and dimethyl sulfoxide (non-HBD) on the acidities of m- and p-substituted phenols, (d) partition coefficients of non-HBD solutes between solvent bilayers, and (e) family relationships between proton transfer (and non-protonic Lewis acid) basicities and corresponding β values for monomer HBA. A comprehensive summary of LSER with references is given.

Linear solvation energy relations

A brief analysis is presnted of the current understanding of substituent perturbations in monosubstituted benzenes as determined by substituent induced carbon chemical shifts. A critical tabulation of the four substituent chemical shifts is given for c. 700 monosubstituted benzenes.

13C substituent effects in monosubstituted benzenes

Fluorocarbons, organic molecules with carbon skeletons and fluorine "skins", differ fundamentally from their hydrocarbon counterparts in interesting and useful ways. A selection of the myriad applications fluorocarbons and their derivatives have found in modern life is described and related to molecular properties. Salient aspects of the nature and reactivity of fluorocarbon compounds are highlighted by comparison with their more familiar hydrocarbon analogues.

Perspective on Fluorocarbon Chemistry

Quantitative measures of solvent polarity.

Nonadditive carbon-13 nuclear magnetic resonance substituent shifts in 1,4-disubstituted benzenes. Nonlinear resonance and shift-charge ratio effects

Para-substituent C-13 chemical shifts in substituted benzenes. 1. Updating the .sigma.R0 scale and analysis of aprotic solvent effects

13 C Substituent chemical shifts of the carbonyl sites in the side-chains of meta- and para-substituted benzenes of the type XC6H4COZ have been measured. Analysis of this data using the dual substituent parameter method shows that inductive effects are predominant. The reverse inductive contribution observed is explained in terms of a π-polarization mechanism. Critical support for this mechanism is obtained from additional series where the carbonyl is complexed with Lewis acids. The concepts of ‘extened’ and ‘localized’π-polarization are discussed.

Carbon-13 substituent chemical shifts in the side-chain carbons of aromatic systems: the importance of π-polarization in determining chemical shifts

Carbon-13 chemical shifts have been measured for the side-chain carbon atoms of a number of meta- and para-disubstituted benzenes. The side chains examined were CN, CF3, Ac, CO2Et, Me, OMe and NMe2. The substituent-induced 13C shifts of these side chains were related to Hammett substituent effects by the Dual Substituent Parameter method and showed a widely varying dependence upon the blend of inductive and resonance effects. The transmission of substituent effects through aromatic systems and the factors that influence 13C shifts are discussed.

John Bromilow

Papers

Nonadditive carbon-13 nuclear magnetic resonance substituent shifts in 1,4-disubstituted benzenes. Nonlinear resonance and shift-charge ratio effects

Para-substituent C-13 chemical shifts in substituted benzenes. 1. Updating the .sigma.R0 scale and analysis of aprotic solvent effects

Carbon-13 substituent chemical shifts in the side-chain carbons of aromatic systems: the importance of π-polarization in determining chemical shifts

Substituent effects on the carbon-13 N.M.R. chemical shifts of side-chain carbons in aromatic systems

Nonadditive carbon-13 substituent and solvent effects in substituted benzenes