Protonated ethane. A theoretical investigation of C[sub 2]H[sub 7][sup +] structures and energies
- Universitaet Erlangen-Nuernberg (Germany)
- Yale Univ., New Haven, CT (United States)
- Univ. of Georgia, Athens, GA (United States)
- Univ. of Calgary, Alberta (Canada)
The C[sub 2]H[sub 7][sup +] potential energy surface was characterized by high-level ab initio calculations. The effects of electron correlation on geometries and relative energies are substantial. At MP4(SDTQ)/6-311G**//MP2(full)/6-31G**, the global minimum is the C-C protonated structure 1, 4.4 kcal/mol (corrected to 298 K) more stable than the C-H protonated form 3. The proton affinity of ethane to give 1 (142.5 kcal/mol) is 12.5 kcal/mol greater than that of methane (130 kcal/mol). Methane adds to the methyl cation, leading to 1 without activation energy. Barriers for intramolecular hydrogen interchange are lower than the dissociation energy into the ethyl cation and hydrogen, consistent with the experimental observation that deuterium scrambling is faster than dissociation. C[sub 2]H[sub 7][sup +] loses H[sub 2] by 1,1-elimination in an endothermic (10.6 kcal/mol) process. Three frequencies deduced experimentally for C[sub 2]H[sub 7][sup +] correspond to those computed for 1, but neither 2, the H[sub 2]-rotated C-H protonated form, nor 3 can explain the other set of experimental spectral data. Complexes between H[sub 2] and bridged C[sub 2]H[sub 5][sup +] were located, but they are too weakly bonded to be detected experimentally. 45 refs., 3 figs., 9 tabs.
- OSTI ID:
- 7165934
- Journal Information:
- Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 116:8; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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ALKANES
CARBON COMPOUNDS
CARBONIUM COMPOUNDS
CATIONS
CHARGED PARTICLES
COMPUTERIZED SIMULATION
DATA
DEUTERIUM COMPOUNDS
ENERGY LEVELS
ENTHALPY
ENTROPY
ETHANE
EXCITED STATES
EXPERIMENTAL DATA
HYDROCARBONS
HYDROGEN COMPOUNDS
INFORMATION
INFRARED SPECTRA
IONS
ISOMERS
METHANE
NUMERICAL DATA
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
SIMULATION
SPECTRA
THEORETICAL DATA
THERMODYNAMIC PROPERTIES
VIBRATIONAL STATES