Role of ion-neutral complexes during acid-catalyzed dehydration of ethanol in the gas phase
- Ecole Polytechnique, Palaiseau (France)
Acid-catalyzed dehydration of ethanol in the gas phase has been studied both theoretically and experimentally. Molecular orbital calculations have been done at the MP3/6-31G*//6-31G* level with correction of the zero-point vibrational energy. Protonated ethanol, 1 is predicted to isomerize easily into the C{sub 2}H{sub 4} {hor ellipsis} H {hor ellipsis} OH{sub 2}{sup +} complex, 2 (activation energy 120 kJ/mol). This result is in agreement with the observation of a near statistical hydrogen exchange preceding the dehydration reaction 1 {yields} C{sub 2}H{sub 4} + H{sub 3}O{sup +}. In the case of the water-solvated ion C{sub 2}H{sub 5}OH{sub 2} {hor ellipsis} OH{sub 2}{sup +}, 5, isomerization into a proton-bound complex C{sub 2}H{sub 4} {hor ellipsis} H{sub 5}O{sub 2}{sup +}, 6, needs a larger amount of energy (ca. 180 kJ/mol). Again the calculations agree with experiments: the important activation energy for the process 5 {yields} 6 prevents hydrogen exchanges and ethene elimination. Extension of these calculations to higher systems is discussed.
- OSTI ID:
- 5964914
- Journal Information:
- Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 112:25; ISSN 0002-7863; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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100200* -- Synthetic Fuels-- Production-- (1990-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ALCOHOLS
BOND ANGLE
BOND LENGTHS
CATALYSIS
CHEMICAL REACTION KINETICS
DEHYDRATION
DIMENSIONS
EIGENVALUES
ENERGY
ENTHALPY
ETHANOL
FORMATION HEAT
HARTREE-FOCK METHOD
HIGH VACUUM
HOMOGENEOUS CATALYSIS
HYDROXY COMPOUNDS
ION PAIRS
KINETICS
LENGTH
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
POTENTIAL ENERGY
REACTION HEAT
REACTION INTERMEDIATES
REACTION KINETICS
THERMODYNAMIC PROPERTIES