Deuterium isotope exchange between molecular hydrogen and cyclopentylamine1

Abstract

Over the temperature range −68 to −10 °C the ability of the alkali metal cyclopentylamide salts to catalyze deuterium exchange between D2 and cyclopentylamine (CPA) is in the order [Formula: see text] The rate constant ratio at −68 °C for CsCPA/LiCPA is > 103. The measured Arrhenius activation parameters and kinetic isotope effect data are only slightly different for the Li and Na salts. The in-solution exchange reaction is so fast for the KCPA and CsCPA catalysts that rate constants independent of mass transfer could not be measured for them in the stirred gas/liquid reactor even at −68 °C.The gas solubility isotope effect, sie = [D2]/[H2], has been determined in CPA over the range −50 to +25 °C. From the values obtained (e.g. 1.08 at 25 °C, 1.10 at −25 °C) and the limited literature data available it appears that the sie for hydrogen gas may be greater for polar than for nonpolar solvents.