Ab initio molecular orbital investigation of the unimolecular decomposition of CH[sub 3]SiH[sub 2][sup +]

Journal Article · Thu Jan 05 04:00:00 EST 1995 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100001a026· OSTI ID:6868179

Gordon, M S; Pederson, L A ^[1]; Bakhtiar, R; Jacobson, D B ^[2]

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1. Iowa State Univ., Ames, IA (United States) Ames Research Lab., IA (United States)
2. North Dakota State Univ., Fargo, ND (United States)

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.

• OSTI ID: 6868179
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 99:1; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400800 -- Combustion
Pyrolysis
& High-Temperature Chemistry
661300 -- Other Aspects of Physical Science-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CALCULATION METHODS
CATIONS
CHARGED PARTICLES
CHEMICAL ACTIVATION
CHEMICAL REACTIONS
COMPILED DATA
DATA
DECOMPOSITION
DEHYDROGENATION
ELECTRONIC STRUCTURE
ENTHALPY
HARTREE-FOCK METHOD
HYDRIDES
HYDROGEN COMPOUNDS
INFORMATION
IONS
MOLECULAR ORBITAL METHOD
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
PHYSICAL PROPERTIES
SADDLE-POINT METHOD
SILANES
SILICON COMPOUNDS
THERMOCHEMICAL PROCESSES
THERMODYNAMIC PROPERTIES