| Popis: |
Exchange-rate measurements of water protons and deuterons in aqueous solutions of acetic, malonic and glutaric acid by the NMR T2 Carr-Purcell method, employing oxygen-17-enriched water, are reported. In contrast to previous results on acetic-acid solutions, intermolecular proton exchange via solvent between COOH and COO− groups is found to contribute considerably to the exchange rate for all three acids investigated. The rate constants necessary for the calculation of the proton residence time in the COOH groups have been determined. Observed deuterium isotope effects on the rate constants for hydrogen-ion and acetic-acid-catalyzed exchange are discussed in terms of fractionation-factor theory. |
