Phenomenological description of the acidity of the citric acid and its deprotonated species: informational-theoretical study

• Published in: Journal of molecular modeling Vol. 29; no. 8; p. 253
• Main Authors: Vázquez-Hernández, Hazel, Esquivel, Rodolfo O.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2023; Springer Nature B.V
• Subjects: Acids; Aqueous solutions; Characterization and Evaluation of Materials; Chemical bonds; Chemistry; Chemistry and Materials Science; Citric acid; Computer Appl. in Life Sciences; Computer Applications in Chemistry; Density functional theory; Electron density; Electronic structure; Entropy (Information theory); Fisher information; Information theory; Liability; Molecular Medicine; Original Paper; Sensitivity analysis; Theoretical and Computational Chemistry; Density functionals; Polyprotic acids; Acid–base chemistry; Information theory
• ISSN: 1610-2940; 0948-5023
• DOI: 10.1007/s00894-023-05589-2

Context In spite of the fact that molecular acidity is a fundamental physicochemical property of molecular systems, the vast majority of theoretical studies have focused attention on monoprotic acids and on the prediction of pKa’s . Polyprotic acids, represent a challenge for electronic structure calculations since the multiple acidic sites result in a vast group of species with different conformations and reactivities. In this work, Information-theoretic (IT) concepts of localizability , order and uniformity are applied to the Citric Acid and its deprotonated species through the one-electron density functionals: Shannon entropy ( S ), Fisher information ( I ) and Disequilibrium ( D ), respectively. We pursue the goal of characterizing the acidity of the aforementioned species with the aim to associate the IT concepts to chemical features such as the polarizability of the protonated/deprotonated species, the liability of the acidic sites, atomic electrostatic potentials, covalent bonding. IT analyses looks very promising for future studies on the acidity of specific deprotonation-sites of polyprotic acids. Methods Density functional theory (DFT) calculations were performed with Gaussian 09 program. A sensitivity analysis of the IT-measures was performed for the citric acid and the citrate using B3LYP, B3PW91, BPW91, M05-2X, M06-2X and PBEPBE functionals with the 6-311++g(3df,2p), 6-311++g(d,p), 6.311+g(d,p) and aug-cc-pVDZ basis sets. The rest of the analysis was performed with the M05-2X/6-311+G(d,p) level of theory. Additionally, aqueous media was considered by use of the SMD solvent model. The IT-measures were calculated using a suite of programs developed in our laboratory jointly with the DGRID software package.