Homogeneous Catalysis of Hydrogen Isotope Exchange between D2 and Ethanol by Chlorotris(triphenylphosphine)rhodium(I). I. in Benzene–Ethanol

1974 ◽  
Vol 52 (12) ◽  
pp. 2216-2225 ◽  
Author(s):  
Graeme Strathdee ◽  
Russell Given
Keyword(s):  
Activation Energy ◽  
Isotope Effect ◽  
Homogeneous Catalysis ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Mixed Solvent ◽  
Product Distribution ◽  
Volume Percent ◽  
Relative Stabilities ◽  
Rate Of Activation

The kinetics and mechanism of D2–C2H5OH exchange catalyzed by chlorotris(triphenylphosphine)rhodium(I) have been studied in 50 volume percent benzene-ethanol. In this mixed solvent, the rate of exchange was low and was limited by the rate of transfer of deuterium from dideuteridochlorotris(triphenylphosphine)rhodium(III) to the solvent, and not by the rate of activation of D2. The activation energy for the overall process was relatively low, 35 kJ mol−1. In addition, new data have been presented for the catalysis of H2–D2 exchange in benzene by RhCl(PPh3)3. Analysis of the apparent HD:D2 isotope effect that is observed during D2–C2–H5OH exchange suggests that this effect originates with the relative stabilities of the D2, HD, and H2 adducts with RhCl(PPh3)3, or by control of the HD and H2 product distribution by the H2–D2 equilibration reaction.

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

1974 ◽  
Vol 52 (12) ◽  
pp. 2226-2235 ◽  
Author(s):  
Graeme Strathdee ◽  
Russell Given
Keyword(s):  
Activation Energy ◽  
Computer Simulation ◽  
Exchange Reaction ◽  
Homogeneous Catalysis ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Reaction Rate ◽  
Side Reaction ◽  
Rate Determining Step ◽  
Inverse Isotope Effect

The kinetics and mechanism of D2 exchange catalyzed by RhCl(PPh3)3 have been studied in chloroform–ethanol solutions. Interpretation of the results was complicated by a side reaction of the solvent to yield HCl, RhHCl2(PPh3)2, C2H5Cl, CH2Cl2, Ph3PO, and other phosphorus(V) species. Computer simulation of the exchange reaction was used to show that the observed inverse isotope effect [Formula: see text] could arise only if the rate determining step was the activation of D2, HD, and H2 by RhCl(PPh3)3.The D2 exchange reaction rate was extremely dependent on solvent composition and decreased 30 times between 6 and 96 mol% C2H5OH. The activation energy for D2 exchange was 101 ± 9 kJ mol−1 at 58 mol% C2H5OH, and 86 ± 8 kJ mol−1 at 6 mol% C2H5OH. These data suggested that solvent–catalyst bonding interactions were important.

Homogeneous Catalysis of Hydrogen Isotope Exchange between D2 and Ethanol by Dichlorotris(triphenylphosphine) Ruthenium(II)

1975 ◽  
Vol 53 (10) ◽  
pp. 1402-1409 ◽  
Author(s):  
Graeme Strathdee ◽  
Russell Given
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Homogeneous Catalysis ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Homogeneous Catalyst ◽  
Hydrogen Isotope Exchange ◽  
Temperature Range

Rates of D2–ethanol exchange catalyzed by solutions of dichlorotris(triphenylphosphine) ruthenium(II) in 1:1 benzene–ethanol are reported as a function of the concentrations of ruthenium, deuterium, triphenylphosphine, and HCl. The rates were extremely fast, and approached 10−3 mol D2 l−1 s−1 at 333 K with 1.3 mmol/l Ru. Over the temperature range 263 to 303 K, the apparent activation energy was 85 kJ/mol. The kinetics have been interpreted in terms of a mechanism in which activation of D2 by RuCl2L3 is rate-controlling. A comparison is made between the characteristics of this homogeneous catalyst and those of the related RhClL3.

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