Atmospheric chemistry of 1,4-dioxane

Laboratory studies

Abstract

A pulse radiolysis technique was used to measure the UV absorption spectra of c-C₄H₇O₂ and (c-C₄H₇O₂)O₂ radicals over the range 220–320 nm, σ(c-C₄H₇O₂)_250nm = (5.9 ± 0.6) × 10⁻¹⁸ and σ[(c-C₄H₇O₂)O₂ ]_240nm = (4.8 ± 0.8) × 10⁻¹⁸ cm² molecule⁻¹. The observed self-reaction rate constants for the c-C₄H₇O₂ and (c-C₄H₇O₂)O₂ radicals, defined as −d[c-C₄H₇O₂]/dt = 2k₄[c- C₄H₇O₂]² and −d[(c-C₄H₇O₂)O₂ ]/dt = 2k_5obs[(c-C₄ H₇O₂)O₂]² were k₄ = (3.3 ± 0.4) × 10⁻¹¹ and k_5obs = (7.3 ± 1.2) × 10^{−1 2} cm³ molecule⁻¹ s⁻¹. The rate constants for reactions of (c-C₄H₇O₂)O₂ radicals with NO and NO₂ were k₆ (1.2 ± 0.3) × 10⁻¹¹ and k₇ = (1.3 ± 0.3) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, respectively. The rate constants for the reaction of F atoms with 1,4-dioxane and the reaction of c-C₄H₇O₂ radicals with O₂, were k₃ = (2.4 ± 0.7) × 10⁻¹⁰ and k₂ = (8.8 ± 0.9) × 10⁻¹² cm³ molecule⁻¹ s⁻¹, respectively. A relative rate technique was used to measure the rate constant for the reaction of Cl atoms with 1,4-dioxane, k₁₇ = (2.0 ± 0.3) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹. A long-pathlength FTIR spectrometer coupled to a smog chamber system was used to show that the sole atmospheric fate of the alkoxy radical (c-C₄H₇O₂)O is decomposition via C–C bond scission leading to the formation of H(O)COCH₂CH₂OC(O)H (ethylene glycol diformate).