A pulse radiolysis technique was used to measure the UV absorption spectra of c-C₃H₅O₃(•) and (c-C₃H₅O₃)-O₂(•) radicals over the range 220-300 nm, with σ(c-C₃H₅O₃(«))_{250 nm} = (5.2 ± 0.7) × 10^-18 and σ((c-C₃H₅O₃)-O₂(•)) _{250 nm} = (3.7 ± 0.4) × 10^-18 cm² molecule^-1. The self-reaction rate constant for the c-C₃H₅O₃(•) radicals, defined as d[c-C₃H₅O₃(•)]/dt = 2k₄[c-C₃H₅O₃(•)]², was k₄ = (3.1 ± 0.6) × 10^-11 cm³ molecule^-1 s^-1. The rate constants for reactions of (c-C₃H₅O₃)O₂(•) radicals with NO and NO₂ were k₆ = (5.8 ± 1.4) × 10^-12 and k₇ = (1.1 ± 0.2) × 10^-11 cm³ molecule^-1 s^-1, respectively. The rate constants for the reaction of F atoms with 1,3,5-trioxane and the reaction of c-C₃H₅O₃(•) radicals with O₂ were k₃ = (1.1 ± 0.4) × 10^-10 and k₂ = (7.4 ± 1.1) × 10^-12 cm³ molecule^-1 s^-1, respectively. Relative rate techniques were used to measure the rate constants for the reactions of OH radicals and Cl atoms with 1,3,5-trioxane and Cl atoms with H(O)-COCH₂OC(O)H, k₂₀ = (6.0 ± 1.0) × 10^-12, k₂₄ = (1.0 ± 0.2) × 10^-10, and k₂₅ = (5.1 ± 1.0) × 10^-13 cm³ molecule^-1 s^-1, respectively. FTIR-smog chamber systems were used to show that the atmospheric fate of the alkoxy radical (c-C₃H₅O₃)O(•) is decomposition via C-O bond scission leading to the formation of H(O)-COCH₂OC(O)H (methylene glycol diformate). The IR spectrum of the peroxynitrate (c-C₃H₅O₃)O₂NO₂ is presented. The results are discussed with respect to the atmospheric chemistry of 1,3,5-trioxane.