A variety of theoretical methods is currently available for the analysis of the effects of high pressures on reaction kinetics, ranging from simple empirical correlations to sophisticated molecular dynamics simulations. Most of them operate within the framework of the transition state theory where the concept of activation volume naturally emerges as the pressure derivative of the activation Gibbs energy. Different models of activation volumes are discussed, as well as the effects of high pressures on reaction profiles, temperature-dependent effects of high pressures, and effects of equilibrium and nonequilibrium solvation.
Two main streams in the molecular theories for partial molar volume are reviewed. The first stream is based on the scaled particle theory of liquids and its extension to polyatomic molecules; this has been used successfully in determining the solvation free energy of non-polar solutes in water. The second method employs the Kirkwood-Buff solution theory. This method is coupled to the integral equation theory of molecular liquids to calculate the partial molar volume of polyatomic molecules. The dependence of the partial molar volume on the conformational change of butane and a tripeptide is examined based on these methods.
The utility of high pressure for the understanding of chemical reactions and its applications in organic synthesis is demonstrated for pericyclic reactions (cycloadditions, Cope rearrangements, electrocyclizations and intramolecular Diels-Alder reactions). With the example of the peptide coupling it is shown that pressure is a valuable tool for the control of other reactions than pericyclic reactions, too.
The scope and limitation of high pressure for the catalysis of organic reactions is evaluated. This article focuses on Lewis acid (cycloadditions, epoxide openings, Horner-Wadsworth-Emmons reactions) and palladium catalyzed (Heck-reaction, [3+2] cycloadditions) reactions. Aspects of reactivity (turnover frequencies and turnover rates) as well as selectivity (chemoselectivity, regioselectivity, diastereo- and enantioselectivity) under the influence of pressure will be discussed.
Raman spectra of CO2 and the van-der-Waals compound He (N2) 11 were obtained under nearly hydrostatic pressures up to 40 GPa. The pressure induced changes of the librational spectra suggest that solid CO2 does not transform directly from phase-I (cubic Pa3) to phase-III (orthorhombic Cmca). An intermediate phase-IV. which may involve only minor modifications of phase-I, is formed prior to the transition to Cmca structure. P hases IV and III coexist over some pressure range. The pressure shifts of all four Raman active librons of phase-III were determined over a wide pressure range and are compared to previous theoretical results. Spectra of external and internal modes of the van-der-Waals compound He (N2) 11 are very similar to those of ε-N2 and imply a close relationship between the structures of He (N2) 11 and ε-N2. The observed splitting of the main vibron of isotopic species 14N-15N indicates that in addition to factor-group interactions site effects are responsible for the observed splittings of the 14N2 main vibron of He (N2) 11.
We produced a long-pulsed dye laser with no Q-switch for the shock-wave measurement or time-resolved spectroscopy under shock compression of solids. The average output power of this laser was larger than 13 kW (effective pulse duration ; ∼50 μs). This laser has been used as a light source for the Hugoniot measurement of solids by the inclined-mirror method combined with a rotating-mirror type streak camera. It was confirmed that the time resolution of Hugoniot measurement increased to higher than 1 ns.