Steric effect in the formation of hydrogen bonded complexes of isopropylamine with alicyclic ethers by ultrasonic and DFT approach

Abstract

Experimental (acoustical) and theoretical (DFT) analyses have been undertaken to unravel the possibility of hydrogen bonded complexes of isopropylamine (IPA) with two industrially important cyclic ethers, tetrahydrofuran (THF) and 1,4 dioxane (DIOX) in n – hexane at 303.15 K and at atmospheric pressure. The trend in acoustical and excess parameters with concentration revealed the dominance of structure breaking behavior of like molecules of solute components and formation of intermolecular H-bonding between IPA and ethers in the two ternary systems at room temperature. The data obtained through DFT studies further support the existence of intermolecular H-bond between amine and ethers. The strength of interactions has been assessed from the formation constants (K) determined by acoustic method and interaction energies by DFT respectively. The reduced density gradient (RDG) and non-covalent interaction (NCI) plots clearly exhibit the presence of intermolecular interactions in the two systems. The stability of these complexes and the strength of the interactions are explained with the structure of ether. Comparison of K and interaction energy values in the present study with those obtained in n-propylamine interactions with ethers showed steric effect in the formation of complex of IPA with the two ethers.