Ab Initio Molecular Orbital Investigation of the Unimolecular Decomposition of CH3SiH2+
| Autor: | Mark S. Gordon, R. Bakhtiar, Lisa A. Pederson, D. B. Jacobson |
|---|---|
| Rok vydání: | 1995 |
| Předmět: | |
| Zdroj: | The Journal of Physical Chemistry. 99:148-153 |
| ISSN: | 1541-5740 0022-3654 |
| DOI: | 10.1021/j100001a026 |
| Popis: | The potential energy surface for the decomposition of CH[sub 3]SiH[sub 2][sup +] was studied by ab initio electronic structure theory. At the MP2/6-31G(d,p) level of theory, CH[sub 3]SiH[sub 2][sup +] is the only minimum energy structure on the SiCH[sub 3][sup +] potential energy surface. Lower levels of theory reported that [sup +]CH[sub 2]SiH[sub 3] was also a local minimum, about 40 kcal/mol higher in energy with only a small (ca. 1-2 kcal/mol) barrier for conversion back to CH[sub 3]SiH[sub 2][sup +]. However, at higher levels of theory, the C[sub s] structure of [sup +]CH[sub 2]SiH[sub 3] has an imaginary frequency, indicating that it is a saddle point rather than a local minimum on the potential energy surface. The 0 K reaction enthalpies for 1,1-dehydrogenation from silicon, 1,2-dehydrogenation, 1,1-dehydrogenation from carbon, and demethanation were calculated to be 30.2, 69.1, 107.3, and 45.3 kcal/mol, respectively. Activation energies (0 K) were calculated at the MP4/6-311++G(2df,2pd) level of theory with the classical barriers subsequently adjusted for zero-point vibrational energies. The 0 K activation energies for 1,1-dehydrogenation from silicon, 1,2-dehydrogenation, and demethanation are predicted to be 66.6, 72.7, and 73.0 kcal/mol, respectively. 52 refs., 5 figs., 2 tabs. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|