10.1021/ja01640a072
The study investigates the kinetics of hydrogen exchange between phosphine (PH?) and water containing 3% deuterium. The researchers measured the rate of approach to equilibrium by tracking the uptake of deuterium in phosphine. They found that under conditions where diffusion from the gaseous to the liquid phase is not rate-determining, the fraction of exchange follows the McKay rate law. The study involved using various buffer solutions, including those with acids like mandelic, formic, benzoic, acetic, and trimethylacetic acids, to explore acid catalysis. For base catalysis, sodium carbonate-sodium bicarbonate, disodium phosphate-trisodium phosphate buffers, and unbuffered 0.01 M sodium hydroxide were used. The experiments revealed that the reaction is first order with respect to hydronium ion (H?O?) and hydroxyl ion (OH?) concentration, with rate constants of 3.6 liters/mole second and 0.40 liters/mole second at 27°C, respectively. The study also explored the effects of general acid and base catalysis, inert salt concentration, phosphine pressure, and temperature on the exchange rate. The results provided insights into the acid and base properties of phosphine in aqueous solution, with estimates of the base dissociation constant (KB) and acid dissociation constant (KA) of phosphine.
