In the present work, the free energy solvation of H + , ΔG sol H + , is estimated in various important nonaqueous solvents including alcohols and polar aprotic solvents, semiempirically. The selected solvents are methanol, ethanol, 2-propanol, 2-methyl-2-propanol, dimethyl sulfoxide, dimethylformamide, and acetonitrile. The value of ΔG sol H + in 2-propanol and 2-methyl-2-propanol were reported for the first time. The estimated values of ΔG sol H + were used to predict the acidity constants (pK a ) of different compounds in the selected solvents. These pK a values had better agreement with the experimental values than the corresponding values obtained using the other ΔG sol H + reported in literature. This confirmed that the values of ΔG sol H +, predicted in this work, are reasonable. The calculated pK a values of selected compounds in nonaqueous solvents were further corrected by accounting for the error of the applied computational method for predicting the pK a values of the compounds in water. New correlation equations were proposed and used to estimate the pK a values of carboxylic acids (aliphatic and aromatic derivatives), phenol derivatives, a series of active pharmaceutical ingredients, and some anti-inflammatory agents in the considered solvents when their experimental pK a values are known in water. The calculations presented in this work were performed at four different levels of theory including B3LYP, M062X, MP2, and CCSD using 6-311++G(d,p) basis set, separately.

The solvation Gibbs free energies (SGFE) of 39 ions were estimated in protic and aprotic solvents including methanol, ethanol, N,N-dimethylformamide (DMF) and acetonitrile (ACN) using a proposed approach. In this method, the error of the applied computational method, used for estimating the SGFE of a specific ion in water and dimethyl sulfoxide (DMSO) solvents, was used as a reference value to correct the calculated SGFE of the ion in other protic and aprotic solvents, respectively. The estimated values of SGFE of ions, obtained in this work, show good agreement with those obtained using the other methods reported in literature. New correlation equations were also proposed for correlating the estimated values of SGFE of ions in a specific solvent to the corresponding values in water and DMSO for protic and aprotic solvent. By using the proposed method in this work, it is possible to estimate the values of SGFE of ions in the solvents that there are no experimental and theoretical reports on them in literature provided that the appropriate and correct reference solvent is selected. Typically, this method was applied on two most popular solvents in organic chemistry including acetone and 1-propanol to estimate the SGFE of the considered ions in them for the first time.

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