In this review, we outline the general aspects of the effect of pressure on chemical reactions and related phenomena in the condensed phases. To make it clear to what extent the high pressure study has been developed in this field, we look back the situation of the 1920's. It is illustrated here how useful high pressure is for testing theoretical models for chemical reaction dynamics, elucidating the mechanism of chemical and biological reaction processes, synthesizing new materials, and developing new technologies for processing foods and hazardous materials. Main problems concerning the theoretical models for the rate constant in the liquid phase are summarized.
Recent progress on the high pressure mediated organic sysntesis is summarized. Substitution reactions of a alcohols, hydrolysis of esters, SNAr reactions, and some organometallic reac-tions are accelerated by high pressure.
The high pressure apparatus are now only moderately expensive, and can be employed, usefully and without much extra effort, in a much wide context than that originally envisaged. This article deals with the recent developments made in such fields as 1) Diels-Alder reaction, 2) 1, 3-Bipolar reaction, 3) nucleophilic substitution, 4) Mannich reaction.
Photoisomerization reactions, which usually involve large amplitude motion of a bulky group twisting around a molecular axis, are often used to test theories of dynamic solvent effects, since the rate of isomerization depends critically on the frictional forces exerted by the solvent molecules. The photoreaction can be initiated with a short pulse of light, and their progress can be monitored by similarly fast time - resolved techniques. The experimental results of the solvent viscosity effect have been analyzed in terms of the Kramers theory or its extended theories developed more recently. In this article the theoretical implication of the dynamic solvent effect is briefly looked into, and its application to some recent experimental results for photoisomerization reactions studied by high - pressure method is reviewed.
Viscosity effect through high pressure on the fast bimolecular reaction involved in the photochemical processes in solution has been reviewed; the systems selected in this article are (1) excimer and exciplex formation reactions, (2) cycloaddition reactions between singlet oxygen and furans, and (3) singlet and triplet quenching by molecular oxygen of anthracene derivatives. For these systems, the contribution by diffusion to the reactions is described.
This article presents the results of high - pressure kinetic study of slow thermal isomerizations (eq. 1) in viscous solvents. The results clearly demonstrated that the analysis based on the transition state theory (TST) becomes invalid only under extremely viscous conditions. By in - serting the observed rate constants and the extrapolated TST - expected rate constants to eq. 2, diffusion - limited rate constants kdif were estimated. The values thus obtained gave linear Ar - rhenius plots suggesting the present reactions proceed via two - step mechanism, namely, a dif - fusion - limited rate process followed by an activation - limited one.
The high - pressure, high - resolution nuclear magnetic resonance (HPHR - NMR) spectroscopy represents one of the most important and indispensable tools for studying high - pressure chemistry, biochemistry, and physics at the atomic and molecular level. After reviewing briefly the advances in HPHR - NMR, I describe in detail the two types of pressure - resisting glass cell techniques for HPHR - NMR, and povide some examples of the experimental application of these handy - type devices to the studies of pressure - induced structural changes in simple organic molecules.
The history of high - pressure ESR techniques applied to solution chemistry has been surveyed briefly, and our recent investigations have been reviewed. The results are summarized as follows: (1) The rate of spin exchange reactions of nitroxides is diffusion - controlled, and the activation volume is closely related to that for diffusive processes. (2) The rates of spin - lattice relaxation for the photo - reduced products of 2, 5 - di - tert - butyl -1, 4 - benzoquinone (2, 5 - DBQ) were estimated at various pressures. (3) From the pressure effects on the ESR signal, aspects of di-tert-butyl nitroxide (DTBN) included in cyclodextrins were inferred. (4) The information on the rotational motion of spin - labeled long - chain molecules in solutions was obtained from the anisotropic ESR signals.
A trend of measurements of high pressure with an accuracy of better than ±0. 1% in the range up to 1 GPa is described. The instruments used are the dead - weight piston manometer, the manganin resistance manometer and strain - gauge type pressure transducer. The piston manometers are available commertially with an accuracy of ±0. 01 %. The secondary instruments should be calibrated against the primary but have become very convenient to use due to the progress of the digital electronic indicator.
Deep-focus earthquakes occur at depths from the earth's surface up to 680 km (corresponding to pressure of 24 GPa). They occur only in the restricted areas in the earth, or the subduction zones. There have been many studies on the nature of the deep-focus earthquakes, but they have not been widely accepted since each model has both advantage and disadvantage to explain the observation facts and the physical, chemical and mechanical properties of rocks and minerals. Recently, two new models are proposed based on the high pressure experiments, to - gether with our understanding of the structure of the subduction zone. One is the transformation faulting (or anticrack faulting) model, and the other is the amorphization model. In this article, these new models inferred from high pressure experiments are reviewed with the brief history of the finding of deep - focus earthquakes and of the studies of their mechanism.
The application of HIP (hot isostatic pressing) technology to cutting tools began with highspeed steels at the end of the 1960s, followed by cemented carbide sintered bodies in 1970. In 1977, HIP technology was used in Japan in the mass production of alumina ceramic cutting tools, for the first time in the world. Ceramic cutting tools require high fracture toughness. The introduction of HIP technology into the manuf acting process has enhanced materials strength and fracture toughness by enabling the production of ceramic materials with finer and more uniform grain. Hot isostatic pressing is unquestionably one of the most important processes for the pro-duction of ceramic cutting tools.
Ishizuka's designs with the characteristic use of a hard sintered alumina cylinder permitted to replace the conventional die material of tungsten carbide with steels which were more ready for the construction of larger components. Thus larger apparatuses were built for the diamond production with a 7000- ton hydraulic press. The most urgent problem in the operation was how to prepare cylinders fast enough to keep pace with the scheduled production.
Selection and machining of a gasket is the base of diamond anvil technique. Mechnical property of the gasket material primarily affects to the thickness of the sample chamber. The way of selection and the machining of the gasket, as well as the compression technique of diamond anvil, are described.