Aldol reactions, montmorillonite active sites

Circulation flow system, measurement of reaction rate, 28 175-178 Clausius-Clapeyron equation, 38 171 Clay see also specific types color tests, 27 101 compensation behavior, 26 304-307 minerals, ship-in-bottle synthesis, metal clusters, 38 368-379 organic syntheses on, 38 264-279 active sites on montmorillonite for aldol reaction, 38 268-269 aldol condensation of enolsilanes with aldehydes and acetals, 38 265-273 Al-Mont acid strength, 38 270-271, 273 comparison of catalysis between Al-Mont and trifluorometfaanesulfonic acid, 38 269-270... 

Amount of Active Sites on Montmorillonite for Aldol Reaction... 

The diastereoselectivity of the reaction was independent of the catalyst but was affected by the nature of the solvent. The threo isomer was preferentially formed in toluene, while the erythro isomer was formed in 1,2-dimethoxy-ethane. The proton-exchanged montmorillonite (H+-mont) showed similar activity and diasteroselectivity to Al3+-mont. This fact suggests that the exchangeable Al3+ cations in the montmorillonite do not function as Lewis acid sites and it is the Bronsted acid sites that are essential for catalysis of the aldol reaction. 

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