Preparation of N-alkylamides of highly methylated (HM) citrus pectin

Abstract

N-Alkylamides of highly methylated (HM) citrus pectin (DM = 73%) were prepared using heterogeneous amino-de-alkoxylation (aminolysis) with five selected n-alkylamines. The reaction was carried out in N,N-dimethylformamide at 8°C (n-butylamine), 25°C (n-hexylamine), and 45°C (n-octylamine, n-dodecylamine and n-octadecylamine). All the derivatives were converted into acid forms by washing with acidic water-ethanol mixture. The products were analysed by organic elemental analysis, diffusion reflection FT-IR spectroscopy and by 13C CP/MAS NMR. Both FT-IR and NMR spectra indicate the presence of alkylamide substituents bound to pectin. The degrees of amidation (DA) of the derivatives and molar and mass reaction yields (Ymand Yn) were calculated based on the results of elemental analysis. The DA values of the N-alkylamides were 39–55% that corresponded to Ynof 54–75%.