Polar Solvents, Acid-base Ionization Equilibrium Constant Of The Theory

Hydrogen bonding plays a critical role in a wide range of chemical and biological phenomena. The hydrogen bonds not only affect the structure and stability of molecular and bio-molecular complexes, but also influent many chemical, physical, and biological processes. Bring the hydrogen-bonded theory to the acid-base scale as the new subject which has attracted considerable attention over the years. The theoretical study of the pKαvalue of organic acids is can supply the experiment test method, it also disclosures the phenomenon and the essence of ionization more and more. So, it will be very interesting and guiding meanings subject. And it is expected to make some theoretical studies of the pKαvalue of organic acids, as to make up for the experiment shortage. Solvent effect in the chemical reaction rate, chemical balance, or even in the reaction mechanism is widely exist, at present, both at home and abroad on the solvent effect on the calculation of theoretical chemistry is a hot field.In this paper we first studied the complexes of organic acids, amine, amino acids, used the high-level ab initio approaches to study the clusters- hydration complexes. The optimized geometric parameters and interaction energies are investigated. Next, in the polar solvent (water) we used the different methods (involve the B3LYP and HF methods) and the polarizable continuum model (PCM) to study the pKαvalue of the organics which have different functional groups. We want to know which method adapts to study the pKα. In the last chapter, we used the cluster-continuum model which base on the hydrogen bond to study the pKI of amino acids, at the some time, discussed the optimal number and the position of the solvent molecule.This paper on the use of water molecules in the organic acids, amines, amino acids around the polar groups, creating a molecular clusters, and then explore the corresponding optimal configuration, and build a suitable thermal cycle dynamics, and ultimately achieved a theoretical simulation and the results matched the experimental data better results. We discussed the theoretical method and model to studied the pKαvalue of organic acid, it has meaning to guide the experimentations and further theoretical study in the future.