ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Rate constants for several reactions of inorganic radicals with inorganic anions in aqueous and aqueous/acetonitrile solutions have been measured as a function of temperature by laser flash photolysis. The reactions studied were (1) Cl2- + N3-, (2) Br2- + N3-, (3) Cl2- + SCN-, (4) Br2- + SCN-, (5) SO4- + Cl-, (6) SO4- + CO32-, and (7) N3- + I-. The rate constants were corrected for ionic strength and ranged from 106 to 109 L mol-1 s-1. The Arrhenius activation energies varied from 2 to 12 kJ mol-1 for the first 4 reactions, were higher for reaction 6, and negative for reaction 5. The pre-exponential factors also varied considerably with log A ranging from 5 to 14. The values of k298 decreased in most cases by more than an order of magnitude upon increasing the acetonitrile (ACN) fraction from 0 to 70%. For most reactions, this decrease in k298 was due to changes in log A with little regularity in the small changes observed in Ea. For reaction 7, k298 was practically unchanged due to compensating effects of the changes in Ea and log A with ACN mol fraction, giving an isokinetic relationship. An isokinetic relationship was also observed in the case of reaction 6; Ea and log A change in parallel while changing ACN mol fraction. Reaction 3 (Cl2- + SCN-) was also studied in water/t-butanol and water/acetic acid mixtures. Linear correlation was found between log k and the dielectric constant of the medium for water/ACN and water/t-BuOH but the lines for the two solvent mixtures had different slopes, suggesting specific solvation effects in addition to the primary solvent polarity effects. With water/acetic acid, k decreased and then increased upon addition of acetic acid. © 1993 John Wiley & Sons, Inc.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550250604
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