Pressure jump techniques

For cryptands in which the molecular cavity is larger than in the case of the [l.l.l]-species [78], proton transfer in and out of the cavity can be observed more conveniently. Proton transfer from the inside-monoprotonated cryptands [2.1.1] [79], [2.2.1] [80], and [2.2.2] [81 ] to hydroxide ion in aqueous solution has been studied by the pressure-jump technique, using the conductance change accompanying the shift in equilibrium position after a pressure jump to follow the reaction (Cox et al., 1978). The temperature-jump technique has also been used to study the reactions. If an equilibrium, such as that given in equation (80), can be coupled with the faster acid-base equilibrium of an indicator, then proton transfer from the proton cryptate to hydroxide ion... 

The effect of ion size on the rates of intercalation of NH J, CH3NH+, C2H5NH 3, n-C3H7NHt, i-C3H7NHt, (CH3)2NH , (CH3)3NH+, and (CH3) N+ into Z-4A zeolite has also been investigated using the pressure-jump technique (18). The results shown in Table V illustrate that Z-4A acts like an ion-sieve. For ions with a volume... 

Micelles are extremely dynamic aggregates. Ultrasonic, temperature and pressure jump techniques have been employed to study various equilibrium constants. Rates of uptake of monomers into micellar aggregates are close to diffusion-controlled306. The residence times of the individual surfactant molecules in the aggregate are typically in the order of 1-10 microseconds307, whereas the lifetime of the micellar entity is about 1-100 miliseconds307. Factors that lower the critical micelle concentration usually increase the lifetimes of the micelles as well as the residence times of the surfactant molecules in the micelle. Due to these dynamics, the size and shape of micelles are subject to appreciable structural fluctuations. 

The appearance or disappearance of the U.V. absorption of the carbonyl group can in principle be used for kinetic measurements. Bell and Jensen (1961) applied this method to 1,3-dichloroacetone the reaction is too fast in pure water, but proceeded at a convenient rate in 5% water-I-dioxan mixtures, in which there is about 50% hydration at equilibrium. Catalysis by many acids and bases was observed. Much faster reactions can be studied by relaxation methods, and the pressure-jump technique has been applied to the reaction Me0(OH)2.CO2H MeC0.C02H-hH20 by Strehlow (1962). 

We are studying other self-assembling systems and extending the measurements to lower frequencies. We shall also use the pressure-jump technique for such studies. 

Mikami, N., Sasaki, M., Hachiya, K., Astumian, R. D., Ikeda, T., and Yasunaga, T. (1983). Kinetics of the adsorption-desorption of P04 on the A1203 surface using the pressure-jump technique. J. Phys. Chem. 87, 1454-1458. 

Ashida, M., Sasaki, M., Kan, H., Yasunaga, T., Hachlya, K, and Inoue, T. (1978). Kinetics of proton adsorption-desorption at Ti02-H20 interface by means of pressure jump technique. J. Colloid Interface Sci. 678, 219-225. 

Now the pressure-jump technique will be described with a system consisting of lanthanide oxalate complexes [17]. The technique used a sudden change in pressure to perturb the equilibrium and a conductivity bridge to detect and follow the changes in the system. The course of re-equilibration is recorded by the use of an oscilloscope and a camera. 

Hachiya, K., M. Sasaki, T. Ikeda, N. Mikami, and T. Yasunaga. 1984. Static and kinetic studies of adsorption-desorption of metal ions on a 7-AI2O3 surface. 2. Kinetic study by means of pressure-jump technique. J. Phys. Chem. 88 27-31. 

The kinetics of proton adsorption/desorption on anatase was studied using a pressure jump technique in [179], and rate constants were calculated. Reference [161] presents the kinetics of proton adsorption for TiO2... 

The rate constants for the formation of 1 1 lanthanide-tartrate complexes have been determined by the pressure-jump technique. The values of kt range from... 

Summarizing it should be mentioned that as compared to the Joule heating temperature jump the pressure jump technique offers a wider choice of solvent composition, an extended time range and shorter time intervals between repeats. And finally it has been shown that for organic solvents the temperature jump due to the adiabatic pressure jump causes an equilibrium shift sufficiently large for kinetic measurements [9]. 

In the course of this work the stopped-flow and pressure-jump techniques have been used, both equipped with optical detection. 

The photochemical relaxation method enqployed in this work initiates a chemical reaction by the direct absorption of light into one of the reacting species (1). In contrast, the temperature and pressure-jump techniques perturb the position of equilibrium by changing the conditions of the reaction medium (2), The photochemical dissociation method thus has several inherent advantages over the ten5>erature-jump and related relaxation methods... 

The introduction of pressure as a variable in fast reaction studies goes back to Brower who designed a pressure-jump technique for work under pressure. The temperature-jump technique has been adapted by a few research groups. The field has been reviewed recently (4). 

The catalytic reactions at solid-liquid interfaces of metal oxides have been of great interest to colloid chemists. The adsorption-desorption phenomena of various metal ions on oxides such as Y-AI2O3 have been extensively investigated since adsorption-desorption is a fundamental step in heterogeneous catalytic reactions. Several mechanisms have been proposed by many investigators . Kinetic studies, however, have scarcely been carried out because the reaction is too fast to be measured by ordinary methods. Only a kinetic study on the proton adsorption-desorption at the Ti02-water interface has been reported using the pressure-jump technique by the present authors. ... 

The kinetic measurements were carried out in the aqueous suspension of y-Al203 containing PbCNOg) at 20°C. A typical relaxation curve obtained by means of the pressure-jump technique with conductivity detection is shown in Figure 1(a) in which the electric conductivity increases with the pressure. As seen from Figure 1(a), at the beginning of the relaxation a very fast change in conductivity was also found. To resolve this, measurements were performed by the electric field pulse technique. 

Kinetic studies of micelle formation and dissociation by direct methods are scarce as already mentioned by Tuzar and co-workers [7,114] and later on by Hamley [11]. Informations can be obtained by fast reaction techniques, such as stop-flow, temperature or pressure jump techniques, as well as by steady state methods, for example ultrasonic absorption, NMR, ESR. 

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