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 dm3 s−1 due to the nucleophilic character of IP reaction and the electron withdrawing –COOH groups. With mono- and dianion molecules the k′s are smaller, (6.6 ± 0.7) × 108 and (3.1 ± 3.0) × 107 mol−1 dm3 s−1. In maleic acid k for the monoanion is higher ((1.34 ± 0.03) × 109 mol−1 dm3 s−1) than for protonated and dianion species, (5.6 ± 0.6) × 108 and (3.5 ± 3.1) × 107 mol−1 dm3 s−1. The high k is interpreted in terms of cyclic structure and charge localization between carboxylic groups.