Mechanistic studies of the pathways leading to ethers via coupling of alcohols
- Lehigh Univ., Bethlehem, PA (United States); and others
The reaction mechanisms for the solid acid-catalyzed dehydrative coupling of methanol and ethanol with isobutanol and 2-pentanol to form ethers were examined by using isotope labelling and chiral inversion experiments. When the reactions were carried out at 110{degrees}C and 1 MPa with Et{sup 18}OH and {sup 16}O-isobutanol over Amberlyst-35, 95% of the major product ethyl isobutyl ether (EIBE) contained {sup 16}O, while 96% of the minor product ethyl tertiarybutyl ether (ETBE) contained {sup 18}O. Similar results were obtained with methanol and isobutanol over Nafion-H and Amberlyst-35 catalysts, with MIBE and MTBE as the products. These results indicate that EIBE (MIBE) was produced by a surface-catalyzed S{sub N}2 reaction, while the ETBE (MTBE) product arose via a carbenium intermediate. The analogous reactions carried out over Nafion-H and H-ZSM-5 catalysts with chiral 2-pentanol verified the surface-mediated S{sub N}2 reaction, where in chiral inversion of the product ether was observed relative to the S- and R-2-pentanol reactants. In addition, a remarkable shape selectivity with chiral inversion was observed over the H-ZSM-5 zeolite to selectively form 2-ethoxypentane but not 3-ethoxypentane.
- OSTI ID:
- 126456
- Report Number(s):
- CONF-950402--
- Country of Publication:
- United States
- Language:
- English
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