Radiation chemical reactions of•OH, O•−, N3•and eaqt- witho- and m-hydroxycinnamic acids were studied. The second-orderrateconstantsforthereaction of•OH with ortho and meta isomers in buffer solution at pH7 are 3.9±0.2 × 109 and 4.4 ± 0.3 × 109 dm3 mol-1 s-1 respectively. At pH 3 the rate with the ortho isomer was halved (1.6 ± 0.4 × 109 dm3 mol-1 s-1) but it was unaffected in the case of meta isomer (k = 4.2±0.6 × 109dm3mol-1 s-1). The rate constant in the reaction of N3• with the ortho isomer is lower by an order of magnitude (k = 4.9 ± 0.4 × 108 dm3 mol-1s-1). The rates of the reaction of eaqt- with ortho and meta isomers were found to be diffusion controlled. The transient absorption spectrum measured in the•OH witho-hydroxycinnamic acid exhibited an absorption maximum at 360 nm and in meta isomer the spectrum was blue-shifted (330 nm) with a shoulder at 390 nm. A peak at 420 nm was observed in the reaction of Obb−with theo-isomer whereas the meta isomer has a maximum at 390 and a broad shoulder at 450 nm. In the reaction of the absorption peaks were centred at 370–380 nm in both the isomers. The underlying reaction mechanism is discussed.
Volume 135, 2023
Continuous Article Publishing mode
Click here for Editorial Note on CAP Mode