Ultrasonic and DFT studies of aliphatic amine – Cyclic ether interactions in n-hexane solvent at 303.15K

The structure breaking behavior in n-propyl amine (NPA) and formation of hydrogen bonded complexes between NPA and two industrially important cyclic ethers, tetrahydrofuran (THF) and 1,4 dioxane (DIOX) are analyzed through ultrasonic velocity (u), density (ρ) and viscosity (η) measurements in n – hexane medium at 303.15 K and at atmospheric pressure. Various acoustical and excess thermo-acoustical parameters are computed and their variations with concentration confirmed the presence of relatively strong intermolecular interactions between amine and ether molecules. Stability constants (K) of these complexes are determined by ultrasonic method to assess the strength of the interactions. Extensive DFT analysis is carried out on the optimized geometry of the component molecules and also their complexes in n-hexane. Computed hydrogen bond parameters support the observations made in experimental ultrasonic investigations. NCI and RDG plots for the complexes are discussed in the light of possible non covalent interactions.