Calculating stability constants for a number of aromatic Schiff bases theoretically using AM1 quasi-experimental method and DFT basic method and comparing the results

Abstract

This study includes finding the values of stability constants by theoretical methods and comparing them with the practical values of a number of Schiff bases prepared from vanillin and aniline and their substitutes in the para position using the computational chemical program (Chem Office 2011). Calculation methods can be divided into two main parts. The first part includes molecular mechanics methods (MM2), which are based in their principle of operation on Newton's laws and through which the composite can be configured for accounts. As for the second part, it includes the methods of quantum mechanics, which are divided into the methods of semi-empirical calculations of the extended structure theory, including the method (AM1), as well as the methods of basic calculations, which consist of several methods, including the (DFT) method, which is based on Schrödinger's laws. The variables that were calculated for this study included the presence of two types of variables, one of them being inductive effects such as bond energies and values of angles and charges on the atoms. The other was the energy or steric variables such as Vander Waal forces (VDW) as well as the values of higher occupied molecular orbital (HOMO) and lower non-molecular orbital occupied (LUMO), chemical electronic potential ($\mu$), spherical electrophilic index ($\omega$), hardness ($\eta$), and heat of formation energies ($H_f$). After completing the calculations by theoretical methods and extracting the results, the statistical analysis was carried out using the statistical program (SPSS version 23). And by the methods of single, binary and multiple statistics to find the relationship between the theoretically calculated variables by means of the values of the correlation coefficients ($R^2$). It shows the agreement of the theoretical results with the practical results.