Study of kinetics and absorption spectra of OH adducts of hydroxy derivatives of benzaldehyde and acetophenone

Radiation chemical reactions of (OH)-O-., O.-, N-3(.) and SO4.- With hydrox y derivatives of benzaldehyde and acetophenone were studied. The second-ord er rate constants for the reaction of (OH)-O-. with o-, m- and p-hydroxyben zaldehydes are in the range (5.2-12) x 10(9) dm(3) mol(-1) s(-1), the order being para > meta > ortho. In O.- reaction, a reverse trend (k(para)<k(met a)) with much lower rates was noticed. The transient absorption spectra mea sured in the (OH)-O-. reaction with o- and m-hydroxybenzaldehydes exhibited absorption maxima at 370 and 400 nm, respectively, whereas two peaks centr ed around 325 and 410 nm were seen in the case of pam isomer. The absorptio n at 370 and 325 nm rapidly decayed in ortho and para isomers, with k = 5.5 x 10(5) s(-1) in the latter. The spectra measured in the (OH)-O-. reaction at 10 mus after the pulse are attributed to the phenoxyl radical formed by dehydration reaction, the rates being dependent on the position of the sub stituent. The major pathways in the O.- reaction are electron transfer in t he case of the meta isomer and addition reaction with the para isomer. (C) 2001 Elsevier Science B.V. All rights reserved.