Following solid-acid-catalyzed reactions by MAS NMR spectroscopy in liquid phase--zeolite-catalyzed conversion of cyclohexanol in water.
Angew Chem Int Ed Engl
; 53(2): 479-82, 2014 Jan 07.
Article
in En
| MEDLINE
| ID: mdl-24282024
ABSTRACT
A microautoclave magic angle spinning NMR rotor is developed enabling inâ
situ monitoring of solid-liquid-gas reactions at high temperatures and pressures. It is used in a kinetic and mechanistic study of the reactions of cyclohexanol on zeolite HBEA in 130 °C water. The (13) Câ
spectra show that dehydration of 1-(13) C-cyclohexanol occurs with significant migration of the hydroxy group in cyclohexanol and the double bond in cyclohexene with respect to the (13) C label. A simplified kinetic model shows the E1-type elimination fully accounts for the initial rates of 1-(13) C-cyclohexanol disappearance and the appearance of the differently labeled products, thus suggesting that the cyclohexyl cation undergoes a 1,2-hydride shift competitive with rehydration and deprotonation. Concurrent with the dehydration, trace amounts of dicyclohexyl ether are observed, and in approaching equilibrium, a secondary product, cyclohexyl-1-cyclohexene is formed. Compared to phosphoric acid, HBEA is shown to be a more active catalyst exhibiting a dehydration rate that is 100-fold faster per proton.
Full text:
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Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
Angew Chem Int Ed Engl
Year:
2014
Document type:
Article
Country of publication:
ALEMANHA
/
ALEMANIA
/
DE
/
DEUSTCHLAND
/
GERMANY