Isomerism and Problems With DFT

1 kcal mol less than experiment, but the computed value of the DPE of phenol is 1.2 kcal mol higher than the experiment. When the DPEs are corrected for this error, the phenolic proton is predicted to be 0.4 kcal mol more acidic than the carboxylate proton at B3LYP and 0.9 kcal mol more acidic at G3B3. These computations are in accord with the experimental observation of a surplus of 16 over 

Both the cysteine and tyrosine acidities point out the importance of solvation in solution, the carboxylate proton is lost exclusively for each compound. 

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