Band Intensities in IR Spectra of Hydrogen-Bonded Amides

Abstract

Important place in the study of intermolecular interactions in polymers is reserved by IR spectroscopy, which allow one to determine the type of H-bond, content of associates, their thermodynamic parameters. Interpretation of experimental spectral data is not always synonymous, since in polyamide complex’s equilibrium of various types of intermolecular bond is realized. Thus the theoretical analysis of the vibration spectra of associated molecules must be employed. Recently we calculated the force constants and electro-optical (EOP) parameters of amides. In present study the calculation of the IR spectra of associated molecules of N-methylacetamide was carried out in order to obtain the force constants and EOP of H-bridge, to establish their relation with the observed changes in IR spectra and the character of redistribution of electron density in complex, it’s dependency on association degree. By self- association of NMA molecules not only dimer complex is formed, but also considerably long chains of H-bonded molecules, and the statistics of distribution of associate lengths are manifested in the IR spectra of amide solution. The parameters of such H-bonds are important for understanding the nature of intermolecular interactions in biological systems, membranes, and determination the compatibility of polymers in composition materials.