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Transition‐state geometry and activation energy calculation for the retro‐ene elimination reaction of propene from diallyl sulfide
Author(s) -
Rodríguez Leonardo J.,
Fermín José,
Añez Rafael,
OcandoMavarez Edgar
Publication year - 2002
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.547
Subject(s) - chemistry , transition state , ene reaction , basis set , ab initio , density functional theory , activation energy , propene , computational chemistry , molecular geometry , sulfide , molecular orbital , transition state theory , geometry , molecule , stereochemistry , catalysis , reaction rate constant , organic chemistry , quantum mechanics , physics , kinetics , mathematics
The transition‐state geometry and the activation energy for the retro‐ene elimination of propene from diallyl sulfide were calculated at three levels of ab initio molecular orbital theory [HF, DFT(B3LYP) and MP2] combined with three basis sets (3–21G*, 6–31G* and 6–31 + G**). The activation energies were determined at room temperature and at 375 °C and compared with experimental data. Our calculations lead to transition states that consist of a non‐planar six‐center cyclic structure with a distorted chair‐like geometry. Moreover, the transition‐state geometry has a marked ‘product‐like’ character. We found that the B3LYP/6–31G* level produce activation values closer to the experimental values in a reasonable time. In all cases studied, the activation energies obtained from both the density functional and MP2 are better than those obtained using the Hartree–Fock method, which overestimates the barrier height. Regardless of the level of theory used [HF, DFT(B3LYP) or MP2], the basis sets 6–31G* and 6–31 + G** produce practically the same values of the activation energy; however, the first set is about twice as fast as the second. The transition‐state geometry obtained by different levels showed only slight structural differences. Copyright © 2002 John Wiley & Sons, Ltd.