A pulse radiolysis technique was used to measure the UV absorption spectra of c-C3H5O3(.) and (c-C3H5O3)O-2(.) radicals over the range 220-300 nm, with sigma(c-C3H5O3(.))(250) (nm) = (5.2 +/- 0.7) x 10(-18) and sigma((c-C3H5O3)O-2(.))(250) (nm) = (3.7 +/- 0.4) x 10(-18) cm(2) molecule(-1). The self-reaction rate constant for the c-C3H5O3(.) radicals, defined as d[c-C3H5O3(.)]/dt = 2k(4)[c-C3H5O3(.)](2) was k(4) = (3.1 +/- 0.6) x 10(-11) cm(3) molecule(-1) s(-1). The rate constants for reactions of (c-C3H5O3)O-2(.) radicals with NO and NO2 were k(6) = (5.8 +/- 1.4) x 10(-12) and k(7) = (1.1 +/- 0.2) x 10(-11) cm(3) 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 O-2 were k(3) = (1.1 +/- 0.4) x 10(-10) and k(2) = (7.4 +/- 1.1) x 10(-12) cm(3) 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, k(20) = (6.0 +/- 1.0) x 10(-12), k(24) = (1.0 +/- 0.2) x 10(-10), and k(25) = (5.1 +/- 1.0) x 10(-13) cm(3) 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.