The chemical effects of pressure. Part 1

Abstract

Rate constants between 1 and 3000 atm have been measured for the unimolecular solvolyses of tert.-butyl chloride and benzotrichloride. They show that the effects of pressure on the velocities of liquid phase ionic reactions can be explained in terms of the solvation forces involved. Stearn and Eyring's theory of the influence of pressure is shown to be inadequate.The basic ionization constants of ammonia and methylamine have been measured at 1, 10o0, 2000 and 3000 atm. They confirm the suggestion that an increase in solvention interaction is responsible for the change in basic strength with pressure. The effect of pressure on ionic solvation free energies can be worked out quantitatively from Born's formula.The most extensive and accurate observations of the influence of pressure on liquid-phase chemical reactions were made by Fawcett, Gibson, Perrin and Williams 1-5 a t the Research Department of I.C.I. (Alkali) Ltd., Northwich. These authors measured the rate constants k of a number of simple organic reactions at pressures up to 12,000 atm, and Perrin summarized their work in a paper read at the Favaday Society Discussion on Reaction Kinetics in 1937.5In his review Perrin grouped the reactions into three kinetic classes : (i) " slow " reactions, with small collision factors, which were greatly accelerated by pressure ; (ii) " normal " reactions, with normal collision factors, which were slightly accelerated by pressure ; (iii) a unimolecular decomposition, which was retarded by pressure.

Electrochemistry at High Pressures: A Review

“…These effects are thermodynamically related to the decrease in the total volume that accompanies ionization reactions [23]. The experimental evidence for this increase is reported in the literature [3,4,10,12,29]. In particular Hamman [3] reported a critical compilation of the effects of pressure on ionization equilibria and of volume changes for the ionization of weak electrolyte.…”

“…However, the design suffered from the misalignment of the two electrodes at high pressures and the cell constant was found to change [3]. At a similar time Buchanan and Hamann [10] constructed a glass cell in which pressure was transmitted by liquid mercury. The cell was immersed in insulating oil inside a high-tensile steel pressure vessel in a thermostat tank: the oil transmitted pressure from a separate commercial hand pump and was sealed in the vessel.…”

“…The cell was mounted in a steel pressure vessel similar to that used by Buchanan [10] for conductivity measurements. The HCl solution and the Ag/AgCl electrode, constituting the left-hand side of the cell, were contained in an open-topped commercial electrode made from a rare earth glass which had a negligible alkaline error at pH 13.…”

Pressure and Temperature Effects on the Kinetics of the Alkaline Fading of Organic Dyes in Aqueous Solution

“…Previous work (1,2,3,4) has shown that for a number of reactions in aqueous solution the effects of pressure may be interpreted in terms of the electrostriction of the solvent around ions and dipoles. The present investigation consists of a study of reactions i~lvolving the attack by a hydroxide ion on large organic dye molecules.…”

A Kinetic Approach to the Inactivation of Zinc by Various Soil Constituents.

“…Studies of a variety of reactions (Buchanan and Hamann, 1955) had lead to the conclusion that for reactions in which ions or fairly strong dipoles are concerned, the solvent effects are generally more important than the structural ones. If the electric field is weakened (Laidler, 1965) when the activated complex is formed (as where two bodies of opposite signs come together), there will be some release of bond solvent molecules and the volumes and entropies of activation will be positive.…”