Reaction of 2-hydroxy-2-propyl radical with maleic and fumaric acids in aqueous solution: pH dependence

2-Hydroxy-2-propyl radical reacts with highly different rate coefficients (k) with the three protonation forms of maleic and fumaric acids. With protonated fumaric acid k is high, (2.1 ± 0.4) · 109 mol 1 dm 3s 1 due to the nucleophilic character of IP reaction and the electron withdrawing -COOH groups. With mono- and dianion molecules the k0s are smaller, (6.6 ± 0.7) · 108 and (3.1 ± 3.0) · 107 mol 1 dm 3s 1. In maleic acid k for the monoanion is higher ((1.34 ± 0.03) · 109 mol 1 dm 3s 1) than for protonated and dianion species, (5.6 ± 0.6) · 108 and (3.5 ± 3.1) · 107 mol 1 dm 3 s 1. The high k is interpreted in terms of cyclic structure and charge localization between carboxylic groups.