Hydrogen-deuterium exchange reactions of 16 small rigid anions were examined using D2O, CH3OD, CH3CO2D, and (CF3)2C(CH3)OD. Bimolecular rate constants and extensive computations are reported. These deuterated reagents were used because D2O and CH3OD are weak acids that cannot react via sequential deuteron/proton transfers (i.e., the conventional H/D exchange mechanism of DePuy et al.) with the selected anions, and they provide a means to probe alternative pathways. The relative acidity of CH3CO2D and (CF3)2C(CH3)OD was measured (ΔΔHacid° = 1.1 ± 0.8 kcal mol-1) and their thermodynamic similarity but structural differences (i.e., the presence of a CO in the carboxylic acid but not the alcohol) were exploited to systematically investigate flip-flop and relay mechanisms. This has led to a number of generalizations relating to the occurrence of these pathways.
- 1 1 1 3 3 3-hexafluoro-2-methylpropanol
- Flip-flop and relay mechanisms
- Hydrogen-deuterium exchange