Homogeneous Catalysis of Hydrogen Isotope Exchange Between D₂ and Ethanol by Chlorotris(triphenyIphosphine)rhodium(I). II. In Chloroform-Ethanol

Abstract

GRAEME STRATHDEE and RCSSLLL GIVEN. Can. J. Chem. 52, 2226Chem. 52, (1974. Tine kinetics and n~echanisn~ of $3, exchange catalyzed by RhCI(PPh,), have been studied in chloroform-ethanol solutions. Interpretation of the r e s~~l t s \.;as co~nplicated by a side reaction of the solveiit to yield HCI, R~I H C I , ( P P~, )~, C2H5C1, CH2C12, Ph,PO, and other phosphorus(\/) species. Computer simulation of the exchange reaction was ~lsed to show that the observed inverse isotope effect 2/c,,,lkD2 = 0.85 cou:d arise only if the rate determining step was the activation of D,, HD, and HZ by RhCl(PPh,),.The D, exchange reaction rate was extremely dependent on solvent composition and decreased 30 times between 6 and 96 m o l z C 2 H 5 0 H . The activation energy for D, exchange was 101 1 9 k9 mol-' at 58 m o l z C,K,OH, and 86 t 8 l<J 1x01-' at 6 molql, G,H,OI-I. These data suggested that solvent-catalyst bonding interactions were important.

The Synthesis and Application of Anchored Catalysts in Hydrogen Isotope Exchange Systems. D2 – Protic Solvent Exchange

“…Alternatively, it is possible that the excess HCI added to a c t i~a t e I/ acted as a co-catalyst for D, exchange. We have observed this behavior with RhCI(PPh,), (19).…”