Browsing by Author "Su, Jou Wei"

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Detailed mechanism and kinetics of the reaction of Criegee intermediate CH2OO with HCOOH investigated via infrared identification of conformers of hydroperoxymethyl formate and formic acid anhydride
(2019-10-14)
Chung, Chen-An
;
Su, Jou Wei
;
Lee, Yuan-Pern
;
交大名義發表
;
應用化學系
The reaction of Criegee intermediate CH2OO with HCOOH is important in atmospheric chemistry, but its mechanism and kinetics are little investigated. We recorded time-resolved infrared absorption spectra of transient species produced upon irradiation at 308 nm of a flowing mixture of CH2I2/O-2/N-2/HCOOH at 298 K. Bands of CH2OO were observed initially upon irradiation; their decrease was accompanied with the appearance of several bands near 887, 925, 1052, 1115, 1170, 1342, 1391, and 1760 cm(-1), assigned to the absorption of hydroperoxymethyl formate [HC(O)OCH2OOH, HPMF], that decreased in intensity at a later period with the appearance of absorption bands of the anti-conformer of formic acid anhydride [anti-(HCO)(2)O, FAN] near 998, 1101, 1767, and 1821 cm(-1). The main contributions of the infrared absorption of HPMF are from an open-form conformer, but small contributions from the intramolecular hydrogen-bonded conformer that absorbs near 1070, 1170, and 1732 cm(-1) were identified. Observed infrared spectra of both conformers of HPMF and anti-FAN agree satisfactorily with the anharmonic vibrational wavenumbers and IR intensities predicted with the B3LYP/aug-cc-pVTZ method. We derived a rate coefficient for CH2OO + HCOOH to be k = (1.4 +/- 0.3) x 10(-10) cm(3) molecule(-1) s(-1) from formation of HPMF. We found also that anti-FAN was produced mainly from the open-form conformer with rate coefficient k = (1460 +/- 30) s(-1); the intramolecular hydrogen-bonded conformer of HPMF is stable.