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Ab initio studies of parts of the potential surface for the system C 3 H 6 + HO 2
Author(s) -
Skancke Per N.
Publication year - 1992
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560410405
Subject(s) - chemistry , propene , intramolecular force , ab initio , ethylene , computational chemistry , ab initio quantum chemistry methods , potential energy surface , carbon atom , hydrogen atom , basis set , hydrogen , molecular orbital , molecule , density functional theory , stereochemistry , catalysis , organic chemistry , ring (chemistry) , group (periodic table)
The addition reactions between HO 2 and propene leading to the radical intermediates CH 3 CHCH 2 OOH and CH 3 CHOHCH 2 have been studied by ab initio molecular orbital calculations using a 6‐31 G * basis set and including electron correlation through fourth‐order Møller–Plesset calculations. The intermediates are predicted to have energies of about 5 kcal/mol below the total reactant energies, the complex resulting from the HO 2 attack on the central carbon of propene being slightly preferred. The activation energies for the addition to the terminal carbon and the central carbon are predicted to be 8.5 and 8.0 kcal/mol, respectively, at the highest level of calculation [ MP 4( SDTQ )] with corrections for spin contamination. Spin contamination corrections are found to be very important in the calculation of these values. Referring to previous calculations at the same level for the addition of HO 2 to ethylene [12], we assume that the addition step is the rate‐determining one in the reaction leading to HO and propene oxide. The observed activation energy for this reaction, 14.2 kcal/mol [2], is significantly higher than the predicted one for the addition step. The discrepancy found, 6.2 kcal/mol, is virtually the same as the one encountered in the ethylene case, 6.6 kcal/mol [12]. The barrier to intramolecular hydrogen migration leading to the intermediate radical CH 2 CH 2 CH 2 OOH is found to be 42.6 kcal/mol at the highest level of calculation. Spin contaminiation corrections are not important for this energy.