Page - 93 - in Advanced Chemical Kinetics

an activated alcoholate more prone for β-hydride elimination. Hence, a bimolecular transition state involving the transient catalyst intermediate and either the acid or alcohol is evoked. Robinson observed that the catalytic efficacy was heavily depending on the stoichiome- try of the trifluoroacetic acid, corroborating its involvement in the rate-determining cata- lytic step(s). Figure 1 illustrates the main elemental steps of the proposed catalytic cycle. Commencing with complex A, isopropanol coordination leads to B, which is then ready for extrusion of trifluoroacetic acid. Upon this extrusion, the β-hydride elimination leads to an acetone coordinated complex C, and complex D is then formed by extruding the acetone molecule. Hydrogen formation from complex D occurs by trifluoroacetic acid mediated protonation of the hydride in D, which then also regenerates complex A and thereby closes the catalytic cycle. Figure 1. Main proposed elemental catalytic steps of the Robinson isopropanol AAD system. Best result: TOF = 13 h−1. Catalyst Kinetics and Stability in Homogeneous Alcohol Acceptorless Dehydrogenation http://dx.doi.org/10.5772/intechopen.70654 93