Thermodynamic study of pyridoxine in different solvents and temperatures: DFT study

Abstract

The equivalent conductivities (Λ) of B6 vitamin (pyridoxine) in HշՕ and MeOH were measured at different temperatures between 293 to 313 K, as well as in mixtures of H₂O and MeOH at percentages of 10, 20, 30, 40, and, 50% MeOH at 310 K. All the practical results were mathematically processed using the Lee Wheaton equation, which is applied to the derived conductivity of electrolytes with a similar composition (1:1). This equation calculates various conductivity components, including the equivalent conductance at infinite dilution (Λₒ), the ionic conductivity, the distance between ions (R), and also the constant of ionic aggregation (Ka) at best-fit values of (ϬΛ). The values of these parameters differed from one solvent to another depending on the molecular interactions in the solution and the physical properties of the solvents, such as viscosity and dielectric constant. Finally, thermodynamic quantities for the ion association reaction (ΔG°, ΔH°, and ΔS°) were also studied. Density functional theory (DFT) calculations (B3LYP/6-31G (d,p)) were employed to analyze vitamin B6 in the gas phase and diverse solvents. Three different continuum methods, namely AM1, PM3, and HF, were utilized, followed by DFT. The final method was utilized to explore the effects on its characteristics. KEY WORDS: Electrical conductivity, Lee-Wheaton equation, Theoretical chemistry, DFT. Bull. Chem. Soc. Ethiop. 2025, 39(1), 165-176. DOI: https://dx.doi.org/10.4314/bcse.v39i1.14