The self-reaction of CH3OO· radicals in the presence of water has been studied at 298 K in 1.013×10^5 Pa of synthetic air . Reactants and products are detected by LP-FTIR absorption spectrometer and high-performance liguid chromatography (HPLC). CH3OOH and CH3OOCH3 are proved to be among the products of the self-reaction of CH3OO·. In addition, HOCH2OOH is identified for the first time in the reaction system. The finding of HOCH2OOH shows that the path to form Griegee intermediate ·CH2OO· is possible in the self-reaction of CH3OO·. Ab initio calculations at the G2, G2(MP2) and G2(ful) levels further indicate that it is favorable in thermodynamics for both the self reaction of CH3OO· to form·CH2OO· and the reaction of ·CH2OO· withwater to produce HMHP.

Key words: METHANE, AIR, WATER, PHOTOCHEMICAL REACTION, FREE RADICALS, INFRARED SPECTROPHOTOMETRY, HIGH SPEED LIQUID CHROMATOGRAPHY