Based on the experimental results obtained, the DFT calculations performed (M06-2x/6-311++G (d,p) level of theory; see the Supporting Information), and previous reports, a plausible reaction mechanism is presented in Scheme 3. The visible-light activation of ClO2 • yields chlorine radicals (Cl • ) and singlet oxygen molecules ( 1 O2 * ) through bond rearrangements from Cl-O-Cl to Cl-O-O bonds. The generated Cl • abstracts hydrogen from Cl3C-H to form a trichloromethyl radical (Cl3C • ) and HCl.