Atmospheric chemistry of 1,4-dioxane Laboratory studies

Abstract

A pulse radiolysis technique was used to measure the UV absorption spectra of c-C ₄ H ₇ O ₂ and (c-C ₄ H ₇ O ₂ )O ₂ radicals over the range 220–320 nm, σ(c-C ₄ H ₇ O ₂ ) _250nm = (5.9 ± 0.6) × 10 ⁻¹⁸ and σ[(c-C ₄ H ₇ O ₂ )O ₂ ] _240nm = (4.8 ± 0.8) × 10 ⁻¹⁸ cm ² molecule ⁻¹ . The observed self-reaction rate constants for the c-C ₄ H ₇ O ₂ and (c-C ₄ H ₇ O ₂ )O ₂ radicals, defined as −d[c-C ₄ H ₇ O ₂ ]/dt = 2k ₄ [c- C ₄ H ₇ O ₂ ] ² and −d[(c-C ₄ H ₇ O ₂ )O ₂ ]/dt = 2k _5obs [(c-C ₄ H ₇ O ₂ )O ₂ ] ² were k ₄ = (3.3 ± 0.4) × 10 ⁻¹¹ and k _5obs = (7.3 ± 1.2) × 10 ^{−1 2} cm ³ molecule ⁻¹ s ⁻¹ . The rate constants for reactions of (c-C ₄ H ₇ O ₂ )O ₂ radicals with NO and NO ₂ were k ₆ (1.2 ± 0.3) × 10 ⁻¹¹ and k ₇ = (1.3 ± 0.3) × 10 ⁻¹¹ cm ³ molecule ⁻¹ s ⁻¹ , respectively. The rate constants for the reaction of F atoms with 1,4-dioxane and the reaction of c-C ₄ H ₇ O ₂ radicals with O ₂ , were k ₃ = (2.4 ± 0.7) × 10 ⁻¹⁰ and k ₂ = (8.8 ± 0.9) × 10 ⁻¹² cm ³ 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, k ₁₇ = (2.0 ± 0.3) × 10 ⁻¹⁰ cm ³ 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-C ₄ H ₇ O ₂ )O is decomposition via C–C bond scission leading to the formation of H(O)COCH ₂ CH ₂ OC(O)H (ethylene glycol diformate).