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| Titel: |
Ab initio calculations on the interconversion of homocub-1(9)-ene and homocub-9-ylidene |
| Auteur: |
HROVAT, DAVID A. BORDEN, WESTON THATCHER |
| Verschenen in: |
Molecular physics |
| Paginering: | Jaargang 91 (1997) nr. 5 pagina's 891-895 |
| Jaar: |
1997-08-10 |
| Inhoud: |
Calculations which include dynamic electron correlation beyond the CASSCF level have been carried out for the interconversion of homocub-1(9)-ene (1) and homocub-9-ylidene (2). The geometry of the transition state was also located at the (4/4)CASSCF/6-31G* level and was found to differ significantly from the previously published (2/2)CASSCF/3-21G geometry. In agreement with experiment, calculations at the (2/2)CASSDCI + Q/6-31G* level find 1 and 2 to have free energies at 298 K that differ by only ∼0.1 kcal mol-1. However, the activation energy for the rearrangement of 1 to 2 of Ea = 12.9 kcal mol-1, computed at this level of theory, is considerably higher than the experimental estimate of Ea ≤ 5 kcal mol-1. Additional calculations in which the size of the basis set was increased or in which the active space was expanded to 4 electrons in 4 orbitals suggest that the calculated Ea may be reduced to as low as 8 kcal mol-1. However, there is no indication that higher level calculations would give a value of Ea as low as 5 kcal mol-1. Possible reasons for this apparent disagreement between the calculations and the experiments on the rate of equilibration of 1 and 2 are discussed. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 2 van 20 gevonden artikelen
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