Structural effect on the formation of hydrogen bonded complexes of benzyl amine and n-propyl amine with aromatic ethers through acoustic and thermodynamic parameters.

• Formation of four amines and ethers H-bonded complexes is established through acoustic method. • UV-Vis. Spectral data support the existence of such complexes in n-hexane. • Thermodynamic parameters K, ΔG, ΔH and ΔS obtained by acoustical and optical methods are reported. • ΔG values reveal thermodynamic stability and ΔH data show exothermic nature of complexes. • Structure of amine and ether influences the formation of these complexes. The present work deals with experimental determination of acoustical parameters to investigate the influence of structure of amines and ethers on thermodynamic properties of four hydrogen bonded complexes in n-hexane solvent at four different temperatures in the range 294.15 K-310.15 K. Benzyl amine (BA) and n-propyl amine (NPA) are used as H-donors while anisole (ANI) and diphenyl ether (DPE) act as H-acceptors. The existence of these H-bonded complexes in solution is also supported by UV spectral data. The formation constants (K) of the complexes determined by ultrasonic and UV-Vis. spectral methods at 303.15 K are comparable. Further, it is observed that the interactions in the aliphatic amine - aromatic ether systems are stronger than aralkyl amine (BA) – ether systems. The thermodynamic parameters confirm that all the four complexes are thermodynamically stable and formation of these complexes is exothermic. The sign of ΔS shows there are strong intermolecular interactions between amines and ethers in n-hexane medium. [Display omitted] [ABSTRACT FROM AUTHOR]