ISSN:
0020-7608
Schlagwort(e):
Computational Chemistry and Molecular Modeling
;
Atomic, Molecular and Optical Physics
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Two possible reaction paths for the pyrolysis of the ethylester of glyoxylic acid have been studied by ab initio molecular orbital calculations. The basis sets 3-21G and 6-31G* have been used, and electron correlation has been included by Møller-Plesset calculations up to fourth order. Our calculations indicate that the reaction leading to acid and ethylene through a 6-membered ring transition state is favored relative to a process involving a formyl hydrogen transfer via a 5-membered ring to the alkyl unit leading to ethane, CO, and CO2. The predicted activation energies for these two reactions obtained at the highest level of calculation, MP4(SDTQ)/6-31G*, are 50.4 and 71.7 kcal/mol, respectively. The transition states have RHF wave functions that are stable relative to UHF solutions using the 3-21G basis. The geometry of the transition states and IRC following indicate that both reactions are strongly asynchronous: The C—O bond rupture is virtually completed before hydrogen transfer occurs. For comparative purposes, analogous calculations have been performed for the ethylester of formic acid, where it is confirmed that a 6-membered ring transition state is preferred relative to a 4-membered one by around 42 kcal/mol at the highest level of calculation.
Zusätzliches Material:
3 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/qua.560400405
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