The basicity of organophosphorus compound is of crucial importance in understanding the hydrolysis of organophosphorus pollutants. It is highly valuable to develop a coherent theoretical method that can accurately predict the basicity of organophosphorus compounds based on the first principles. Herein, a first ab initio protocol was developed, which could predict the pKa values of protonated organophosphorus compounds. The gas-phase geometry was optimized by using B3LYP/6-31＋G(d), and the subsequent single point energy and solvation free energy were calculated by using PBEPBE, IEFPCM/Bondi (f＝1.0), respectively. The rms error was 0.7, and the theoretical predictions were also consistent with all the available experimental data. Based on this method, the pKa values of a number of protonated organophosphorus compounds, which are also important organophosphorus pollutants, were reported. Subsequently, the α-substituent effects and the remote substituent effects were compared on the pKa of protonated organophosphorus compounds. The factors that affect the acidity of the protonated heterocyclic organophosphorus compounds were also discussed.

Key words: organophosphorus, pKa, DFT, PCM, hydrolysis