Acidity of the chlorinated phenols: DFT study and experiential affirmation

A quantum mechanical density functional theory (DFT) was successfully developed for the estimation of pK_a values of chlorinated phenols in aqueous solution with a precision of 0.9 pK_a units. The MP2/6-311++G(d,p)//B3LYP/6-31+G(d) level of theory was used for the gas phase calculation. For computation in the solution phase and to calculate the energy difference of the acid-base, the polarized continuum model (PCM) at the HF/6-31G(d,p) level was used. The pK_a value was computed for each involved species using pentachlorophenol (PCP) as a reference molecule. Natural bond orbital (NBO) analysis considering the natural resonance theory (NRT) was carried out on an optimized geometry of studied compounds to give information about the nature of bonds. Graphical abstract Chlorinated phenols.