Reaction of the NO3 radical with some thiophenes:: Kinetic study and a correlation between rate constant and EHOMO

The rate constants and activation energies for the reactions of some thiophenes with the NO3 radical were measured using the absolute fast-flow discharge technique at 263-335 K and low pressure. The proposed Arrhenius expressions for 2-ethylthiophene, 2-propylthiophene, 2,5-dimethylthiophene, and 2-chlorothiophene are k = (4.2 +/- 0.28) x 10(-16) exp[(2280 +/- 70)]/T, k = (7.0 +/- 2) x 10(-18) exp[(3530 +/- 70)]/T, k = (1 +/- 1 x 10(-14) exp[(1648 +/- 240)]/T, and k = (8 +/- 2) x 10(-17) exp[(2000 +/- 200)]/T (k = cm(3) molecule(-1) s(-1)), respectively. The reactions of this radical with 2-chlorothiophene and 3-chlorothiophene were also studied by a relative method in a Teflon static reactor at room temperature and atmospheric pressure. The effect of substitution on thiophene reactivity is discussed, and a relationship between the rate constants and the ionization potential (IP = -E-HOMO) has been proposed. (c) 2006 Wiley Periodicals, Inc.