Abstract

The ionization constant of five acidic compounds derived from n-formylpiperidine was theoretically studied, and in this study, the factors affecting the pKa of ionization constant of acidic compounds derived from n-formylpyridine were found, which are represented by Vander Waals forces, energy levels, hardness, chemical potential, and spherical electrophile index through Conducting a theoretical study of these compounds using two methods of quantum mechanics for the purpose of comparison, which are semi-empirical calculations, including Austin AM1 method, and Ab-initio basic calculations, including (HF) Hartree Fock method using Chem program. Office 2008 and the extent to which these two methods are compatible with the known chemical bases was determined by discussing the theoretical variables that were calculated using the two methods mentioned above to determine which of these two methods is the best in calculating these variables and finding the relationship between the theoretically calculated physical variables with each other and determining their nature.
These constants were linked with the practical values ​​of the ionization constant by conducting a simple and multiple statistical analysis process. The results gave a good relationship with the ionization constant through the high values ​​of the correlation equations (R2) that were obtained.
After conducting the multi-statistical analysis process, it was found that the best variables that affect the ionization constant in the (AM1) method are (MC-N8, Str.), and in the (HF) method are (W, Str.) and the rest of the variables were theoretically excluded because the coefficients of those variables Very few or equal to zero, and therefore these variables were adopted to obtain a relationship with better results, as it is noted that the values ​​of the correlation coefficient in the two methods are ([AM1] {0.9942}), ([HF] {0.9985}). By comparing the theoretical values ​​with the practical ones, it was found that the results of the HF method were closer to the practical results.