A theoretical study of the limits of the acidity of carbon acids in phase transfer catalysis in water and in liquid ammonia

The acidities of a large number of carbon acids have been theoretically calculated for the gas-phase and for DMSO solution. The gas-phase values, both ΔH and ΔG, are very well correlated with the available experimental data. From the calculated ΔG values in DMSO and the pKas in the same solvent, a homogeneous set of pK _a (DMSO) values was devised that was used to generate pK _a (water). These last pK _as were used to establish the limits of the acidity of carbon acids for reactions under PTC conditions both alkylations and H/D exchange. A step further led to the pK _as in liquid ammonia and from them to the virtual use of PTC using liquid ammonia instead of water.