A density functional theory calculations of infrared spectra of galactomannan butyl ether

Abstract

Alkylated derivatives of polysaccharides are widely used in many fields such as construction, medicine and pharmaceuticals. Galactomannan is a common polysaccharide obtained from plants and microorganisms. In this work, the theoretical FTIR spectra of galactomannan butyl ether are calculated using method (DFT+PBE0 density functional) was implemented with Def2-SVP basis set. It is shown the largest total relative error (36.5%) is observed in the theoretical spectrum of galactomannan butyl ether in the position of the butyl group at O14 of the oxygen atom. The smallest relative error (both average (1.1%) and total (14.7%) is observed in the theoretical spectrum of galactomannan butyl ether in the position of the butyl group at O4 of the oxygen atom. The attachment of the butyl group to galactomannan primarily occurs at the O4 oxygen atom of the galactomannan. The synthesized butyl esters of galactomannan were also characterized by optical microscopy and gel permeation chromatography.