Nonenzymatic hydrolysis of 1,2:3,4-diepoxybutane: A kinetic study including pH, temperature, and ion effects

Abstract

1,3-Butadiene is a carcinogenic and mutagenic air pollutant metabolized to butane epoxides, among which 1,2:3,4-diepoxybutane (DEB) exhibits the highest genotoxicity. DEB is also formed by 1,3-butadiene oxidation in the air, producing a direct environmental and occupational exposure. In this paper, we studied the kinetics of the nonenzymatic hydrolysis of DEB at a wide range of pH and temperature, including the catalytic effect of ionic species. The compound degradation involved a general and specific acid-base catalysis of the epoxide ring hydrolysis. DEB had the greatest stability at pH 5–9, when the rates of acid-catalyzed and base-catalyzed hydrolysis are negligible and the neutral hydrolysis predominates. The capability of the buffer anions to accelerate the DEB decay increased in the order H₂PO₄⁻ < HCO₃⁻ < CH₃COO⁻ < HPO₄²⁻ < and CO₃²⁻. The Arrhenius equation well described the influence of temperature on the acid-catalyzed, base-catalyzed, and neutral hydrolysis rate constants. According to the obtained hydrolysis model coupled with the found thermodynamic parameters, the half-life of DEB in natural fresh waters spans from 2 days at 30°C to 31 days at 0°C, but in the laboratory waste adjusted to pH 1or 13, the half-life shortens to 2–3 h at 20°C. Therefore, the results of the paper help to assess the risk of exposure to the genotoxic action of DEB.