Theoretical investigation of the role of intramolecular hydrogen bonding in {beta}-hydroxyethoxy and {beta}-hydroxyethylperoxy radicals in the tropospheric oxidation of ethene
- Univ. of Leuven (Belgium). Dept. of Chemistry
In this work, the authors performed a quantum chemical B3LYP-DFT/6-31G** characterization of the geometries, vibrational frequencies, and relative energies of the various internal-rotation conformers of the title radicals and of the transition structures for the HOCH{sub 2}CH{sub 2}O {r_arrow} CH{sub 2}OH + CH{sub 2}O dissociation, thereby obtaining the first evidence for intramolecular hydrogen bonding in these molecules. For both the peroxy and oxy radicals, some of the equilibrium geometries were found to be stabilized by interactions between the hydroxy H and the (per)oxy O, lowering the energies by 1.5--2.5 kcal/mol, as confirmed by single point CCSD(T) calculations; it is concluded that thermalized populations at ambient temperatures should consist predominantly of the H-bonded rotamers. Furthermore, the hydrogen bond was found to persist in the transition state for dissociation of the H-bonded HOCH{sub 2}CH{sub 2}O rotamers, resulting in an energy barrier calculated to be only 10 kcal/mol, in excellent accord with recent experimental results. Based on the DFT characterizations and using advanced statistical energy partitioning theories, a Master Equation analysis was performed predicting that at 298 K and 1 atm, 38% of the HOCH{sub 2}CH{sub 2}O radicals formed in the atmospheric HOCH{sub 2}CH{sub 2}OO + NO reaction dissociate promptly before collisional stabilization; also, the rate constant of the thermal dissociation of HOCH{sub 2}CH{sub 2}O was theoretically evaluated at 2.1 {times} 10{sup 5} s{sup {minus}1} at 298 K and 1 atm.
- OSTI ID:
- 343538
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 12 Vol. 103; ISSN 1089-5639; ISSN JPCAFH
- Country of Publication:
- United States
- Language:
- English
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