Hydride Transfer: A Dominating Reaction of Ozone with Tertiary Butanol and Formate Ion in Aqueous Solution

Abstract

This article provides evidences that hydride transfer is an important primary step in ozone reactions of formate and tertiary butanol in aqueous media. In both systems, one argument is the fact that the free hydroxyl radical yields are relative low ((40 ± 4)% and (7 ± 0.8)% for formate and tertiary butanol, respectively). Another hint is the high exergonicity of these reactions: ΔG = –249 kJ mol−1 for formate/ozone system and ΔG = –114 kJ mol−1 for hydride transfer followed by a methyl shift in the reaction between tertiary butanol and ozone. In addition, the main product of tertiary butanol ozonolysis is butan-2-one [(89 ± 3)%], a compound that is formed only via hydride transfer. For the reaction of ozone with formate an activation energy of (54.6 ± 1.2) kJ mol−1 and a pre-exponential term of (2.5 ± 1.2) × 1011 were determined (in the presence of tertiary butanol as •OH scavenger) whereas for tertiary butanol the two activation parameters were (68.7 ± 1.9) kJ mol−1 and (2.0 ± 1.5) × 109, respectively.