OH-initiated atmospheric oxidation mechanism of 1-chloronaphthalene (1-CN) was investigated using density functional theory (DFT) calculations. The oxidation is predicted to be initiated by OH addition to the a-positions, and the additions to C4 and C5 are more favorable. 1-CN-OH adducts tend to react with ambient O-2 to produce peroxy intermediates, followed by intramolecular H-shifts producing C10H7OCl and diketone or unimolecular ring closure forming methyl glyoxal and Cl-substituted phthalaldialde-hyde. Despite that the rate constants are influenced by the tunneling factors, intramolecular H-shift reactions are suggested to be more favorable. The OH-determined lifetime of 1-CN is 0.62 days. (C) 2018 Elsevier B.V. All rights reserved.