Kinetics of the reaction of ferrous ions with hydroxyl radicals in the temperature range 25–300 °C

• Published in: Physical chemistry chemical physics : PCCP Vol. 26; no. 5
• Main Authors: Barr, Logan, Conrad, Jacy Kathleen, McGregor, Christine, Perron, Randy, Yakabuskie, Pamela A., Stuart, Craig R.
• Format: Journal Article
• Language: English
• Published: United States Royal Society of Chemistry 11.01.2024
• Subjects: High Temperature; Hydroxyl radical; Iron (II) ions; pulsed electron radiolysis; RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
• ISSN: 1463-9076; 1463-9084

Here, the kinetics and mechanism of the reaction between OH radicals and ferrous ions in the temperature range 25–300 °C were studied using pulse radiolysis. At temperatures <150 °C the rate of reaction is essentially independent of temperature, while at temperatures >150 °C the activation energy is 45.8 ± 3.0 kJ mol—1. The change in activation energy is attributed to a change in the dominant mechanism from hydrogen atom transfer (HAT) to dissociative ligand interchange. The kinetic isotope effect (KIE) was measured by repeating experiments in heavy water. A value of 2.9 was measured at room temperature where HAT is the dominant mechanism. The KIE decreases to zero at temperatures > 150 °C as ligand interchange becomes dominant and the O–H bond is no longer involved in the reaction.