Rate constants of carbonate radical anion reactions with molecules of environmental interest in aqueous solution: A review
2020
Wojnárovits, László | Tóth, Tünde | Takács, Erzsébet
The rate constants of carbonate radical anion (CO₃⁻) reaction with organic molecules, mainly of environmental interest, were collected from the literature and structure effects were discussed together with methods of rate constant determination and reaction mechanisms. These rate constants are essential for modelling chemical processes taking place with participation of reactive radicals in the environment determining the persistence of certain toxic compounds. The rate constants span over a very wide range from 10² to 10⁹ mol⁻¹ dm³ s⁻¹, but, even the highest values are smaller by a factor of 2–5 as the diffusion controlled limit. This survey shows that only those molecules have high rate constants in the 10⁷–10⁹ mol⁻¹ dm³ s⁻¹ range which have special electron rich part(s). These molecules are removed selectively in CO₃⁻ reactions. Such electron rich moiety is the NH₂ group attached to an aromatic ring. High vales were measured e.g., for most of anilines or the sulfonamide antibiotics. –CO group attached to the N-atom (in acetanilides and in phenylurea herbicides), or strong electron withdrawing substituents on benzene ring strongly decrease the rate constant. High values were also measured for aromatic molecules with dissociated –OH group (O⁻, phenoxides). The thioether group (e.g., in amino acids, or in fenthion or phorate insecticides) also activates the molecules in CO₃⁻ reactions.
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