Solvent-jump

The principles and the experimental aspects of the solvent-jump (or concentration-jump) relaxation method are discussed. 

The difference between the regular flow methods (2) and the solvent-jump method is manifested in experimental procedures and in the evaluation of the data as well. 

In contrast to regular flow experiments where the reactants are mixed and the rate of reaction is measured, in solvent-jump experiments an equilibrium solution is perturbed, typically by a sudden dilution or by a sudden mixing with another solvent (Figure 1) and the relaxation time t is measured. Besides the greater simplicity associated with the interpretation of relaxation times instead of rates, the solvent-jump method has obvious advantages in studying association equilibria where the reactants cannot be mixed. 

Figure 1. Schematic diagram of a solvent-jump experiment using a flow system (stopped or continuous) with uniform cross section. Observation (optical detection) is done along the distance coordinate x between d and 1, all counted from the mixing jet.

Solvent-jump relaxation kinetic, equilibrium spectral photometric and relaxation amplitude results are presented on aqueous Triton-... 

The solvent-jump method (1) was used to investigate the relaxation kinetics of aqueous Triton-305 (octylphenyl polyoxyethylene, with X = 30) at 5 C. To facilitate the monitor-... 

The stopped-flow apparatus used in the solvent-jump experiments has been described previously (5). 

Figure 1. Typical solvent-jump relaxation curve (transmitted light intensity I v . time) of the OPE q-AO system at 5, using pretriggering. Monitoring is at A = 493.5 nm.

D. Y. Chao and Z. A. Schelly, J. Phys. Chem., 79, 2734 (1975). Also see article on the "Solvent-Jump Method" in this volume. 

The oxidation of hexacyanoferrate(II) by nitrous acid involves an encounter-controlled reaction between [HFe(CN)6] and the nitrosonium ion. " More conventional nitrosations have also received much attention, as have the use of specific nitrosating agents and the transfer of NO" groups between molecules. The rate constant for the reaction of nitrous acid and methanol (O-nitrosation) is significantly lower than that expected for a diffusion-controlled reaction. Solvent-jump relaxation techniques have been used in the study of the NOCl— 1-butanol reaction in CCI4—HO AC mixtures. 

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