FTIR-smog chamber techniques were used to determine rate constants for the gas-phase reaction of Cl and F atoms with CH ₃ C(O)C(O)CH ₃ and F atoms with CH ₃ C(O)F of (4.0 ± 0.5) x 10 ^-3 , (4.9 ± 0.7) x 10 ^-11 , and (3.6 ± 0.4) x 10 ^-12 cm ³ molecule ^-1 s ^-1 , respectively. Two pathways for the reaction of Cl and F atoms with CH ₃ C(O)C(O)CH ₃ were found: (1a) Cl + CH ₃ C(O)C(O)CH ₃ → HCl + CH ₃ C(O)C(O)CH ₂ ·, (1b) Cl + CH ₃ C(O)C(O)CH ₃ → CH ₃ C(O)Cl + CH ₃ C(O)·, (2a) F + CH ₃ C(O)C(O)CH ₃ → HF + CH ₃ C(O)C(O)CH ₂ ·, (2b) F + CH ₃ C(O)C(O)CH ₃ → CH ₃ C(O)F + CH ₃ C(O)·, with branching ratios of k _1b /(k _1b + k _1a ) = 0.23 ± 0.02 and k _2b /(k _2b + k _2a ) = 0.56 ± 0.09. It was determined that the atmospheric fate of CH ₃ C(O)C(O)CH ₂ O· radicals is decomposition to give HCHO, CO, and CH ₃ C(O)· radicals. Pulse radiolysis coupled to UV absorption spectroscopy was used to study the kinetics of the reaction of F atoms with CH ₃ C(O)C(O)CH ₃ as well as spectra of CH ₃ C(O)C(O)CH ₂ · and CH ₃ C(O)C(O)CH ₂ O ₂ · radicals over the wavelength range 220-400 nm at 295 K. The rate constant for the reaction of F atoms with CH ₃ C(O)C(O)CH ₃ was determined to be (4.6 ± 0.8) x 10 ^-11 cm ³ molecule ^-1 s ^-1 . The absorption cross sections of CH ₃ C(O)C(O)CH ₂ and CH ₃ C-(O)C(O)CH ₂ O ₂ · radicals were (5.4 ± 1.0) x 10 ^-18 at 250 nm and (2.0 ± 0.5) x 10 ^-18 cm ² molecule ^-1 at 320 nm, respectively. Results are discussed with respect to the available database concerning the reaction of Cl and F atoms with organic compounds.