Jump method

Strehlow H and Beoker M 1959 The pressure-jump method for the measurement of rates of ionio reaotions Z. Eiektrochem. 63 457-61... 

The most widely used transient method is the temperature-jump (T-jump) method. This is based on the van t Hoff equation, which describes the temperature dependence of the equilibrium constant. 

The pressure-jump (P-jump) method is based on the pressure dependence of the equilibrium constant, Eq. (4-28), where AV is the molar volume change of the reaction. 

The electric field-jump method is applicable to reactions of ions and dipoles. Application of a powerful electric field to a solution will favor the production of ions from a neutral species, and it will orient dipoles with the direction of the applied field. The method has been used to study metal ion complex formation, the binding of ions to macromolecules, and acid-base reactions. 

Concentration-jump methods, such as the pH-jump technique cited earlier, can be used in relaxation kinetics, but this approach is described later (Section 4.4). 

Metal ion complexation rates have been studied by the T-jump method. ° Divalent nickel and cobalt have coordination numbers of 6, so they can form complexes ML with monodentate ligands L with n = 1—6 or with bidentate ligands, n = 1-3. The ligands are Bronsted bases, and only the conjugate base form undergoes coordination with the metal ion. The complex formation reaction is then... 

The equilibrium binding constant for this 1 1 association is Xu = ki/lLi. The Xu values were measured spectrophotometrically, and the rate constants were determined by the T-jump method (independently of the X,j values), except for substrate No. 6, which could be studied by a conventional mixing technique. Perhaps the most striking feature of these data is the great variability of the rate constants with structure compared with the relative insensitivity of the equilibrium constants. This can be accounted for if the substrate must undergo desolvation before it enters the ligand cavity and then is largely resolvated in the final inclusion complex. ... 

Opposing reactions. Use the data on the right side of Table 3-2, concerning the triphenyl methyl radical, to calculate ki. This experiment refers to the concentration-jump method in which the parent solution was diluted with solvent to twice its initial volume. 

Concentration-jump method. The following disproportionation equilibrium has been studied by the concentration-jump technique 13... 

In the pressure-jump method, the solution is pressurized, usually to several thousand atmospheres. At the desired moment a diaphragm is mechanically ruptured. The... 

Temperature-jump kinetics. The kinetics of complexation of lutetium(III) with anthrani-late ion was studied by the use of a temperature-jump method.25 The principal reaction is... 

Competition reactions ad eosdem, 106 ad eundem, 105 (See also Reactions, trapping) Competitive inhibitor, 92 Complexation equilibria, 145-148 Composite rate constants, 161-164 Concentration-jump method, 52-55 Concurrent reactions, 58-64 Consecutive reactions, 70, 130 Continuous-flow method, 254—255 Control factor, 85 Crossover experiment, 112... 

Taft equation, 229-230 Temperature, effect on rate, 156-160 Temperature-jump method, 256 Termination reaction, 182 Thermodynamic products, 59 Three-halves-order kinetics, 29... 

Temperature jump method. " Stopped flow method. Direct spectrophotometry. 

We start with some background on existing methods that alter the initial distributions in the reactant basin, focusing in particular on the puddle jumping method of Tully and coworkers [69, 110], which is the inspiration for the skewed momenta method developed in the following section. We continue with a description of the skewed momenta method, as applied to (8.48), with numerical examples for each case. We end with a concluding discussion. 

The kinetics of a series of guests that form 2 1 (guest CD) complexes were studied using temperature jump methods.179 183,210 The formation of the 1 1 complex was determined to be fast and to occur within the time resolution of the equipment, while... 

Fig. 23 A plot of the observed pseudo-first-order rate constant for the methanolysis of 0.04mM HPNPP ( , left axis) catalyzed by 0.2mM35 2Zn(II) or 0.04mM methyl /j-nitro-phenyl phosphate (O, right axis) catalyzed by 0.4 mM 35 Zn(II) as a function of the [CH30-]/ [35 Zn(II)] ratio at 25 + 0.1 °C. Experiments done by pH jump method starting at a [CH30-]/ [35 Zn(II)] ratio of 1.0 (vertical dashed line, (pH = 9.5) and adding acid (left) or base (right). Reproduced with permission from ref. 95.

Pressure filters, 76 658-659 horizontal belt, 77 379 thickening, 77 382-388 Pressure gauge, 20 645 Pressure gradients, flow caused by, 9 110 Pressure infiltration, of metal-matrix composites, 76 167-169 Pressure injection, moldings, 10 11 Pressure-jump method, 73 427-428... 

Temperature gradients in microfluidics, 26 968 Temperature-induced gelation, 9 75 Temperature-jump method, 73 425-427 Temperature level (TL)... 

The dimerization reaction is fast and has been studied by the temperature-jump method (70). At 25°C and ionic medium 3.0 M LiC104 the... 

Catalytic reactions of methanol on an Mo(112)-(lX2)-0 surface under a constant flow of CH3OH and 02 (10 6—10 5 Pa) were monitored as a function of reaction time by the temperature-jump method. Total amounts of the products are summarized in Table 8.3. When only CH3OH was fed, the reaction rate exponentially decayed with reaction time. After the reaction ceased in both conditions, the surfaces were covered with nearly 1 ML of C(a) (Table 8.3) and the sharp (1X2) LEED subspots of the surface before the reaction almost disappeared due to an increase in background intensity. As shown in Table 8.3, the selectivity of the reaction at 560 K is similar to that obtained by TPR (Table 8.2). The C(a) species formed with 26% selectivity cover the surface, resulting in the exponential decay of the reaction rate. O(a) species are also formed on the surface but they are desorbed as H20 by reaction with hydrogen atoms. It should be noted that neither C(a) nor a small amount of O(a) change the selectivity in this case. 

Due to the fast kinetics of adsorption/desorption reactions of inorganic ions at the oxide/aqueous interface, few mechanistic studies have been completed that allow a description of the elementary processes occurring (half lives < 1 sec). Over the past five years, relaxation techniques have been utilized in studying fast reactions taking place at electrified interfaces (1-7). In this paper we illustrate the type of information that can be obtained by the pressure-jump method, using as an example a study of Pb2+ adsorption/desorption at the goethite/water interface. 

The electric-field-jump method with electric conductivity detecting system can be applied to reactions occuring on the order of milliseconds to microseconds. The rise time of the applied electric field is much faster than 0.1 ys. The strength of the electric field is 20 kV/cm. The details of the electric-field-jump apparatus can be found elsewhere (9). 

Figure 1. Typical relaxation curve in the aqueous y-A1203 -Cu(N03)2 suspension observed by using the pressure-jump method. [P] = 30 g/dm3, and I = 7.5 x10-3 at 25 °C sweep 20 ms/div.

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