Sonochemical Synthesis of Glucomannan Derivatives with p-Aminobenzoate and Benzotriazole Ligands Hapin Afriyani*(a), Dian Septiani Pratama(a), Devi Nur Anisa (a), Amelia Khairunisa(a), Icha Dwi Lusiana(a)
a. Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Lampung
Jl. Sumantri Brojonegoro 1, Gedong Meneng, Rajabasa, Bandar Lampung, Lampung, 35145, Indonesia
Abstract
Glucomannan is a natural polysaccharide derived from Amorphophallus muelleri (porang) tubers, which possesses outstanding potential as an environmentally friendly functional material. In this study, chemical modification of glucomannan was successfully carried out through two main stages: the formation of a glucomannan-aldehyde intermediate (GA1) and the synthesis of GA pABA and GA BTA derivatives using a sonochemical method. The first stage involved the oxidation of glucomannan with sodium periodate (NaIO4), which cleaved the C2 to C3- bond in the pyranose ring to produce reactive aldehyde groups. Sonication at a frequency of 20 to 40 kHz for 30 to 60 minutes accelerated the formation of GA1 compared to the conventional 24 hour reflux method. In the second stage, GA1 was reacted with p-aminobenzoic acid (pABA) and benzotriazole (BTA) through a reductive amination reaction to yield stable secondary amine derivatives. The imine formation occurred under mildly acidic conditions (pH 5.5) and was subsequently reduced using sodium cyanoborohydride (NaBH3CN) to strengthen the CN bond. The resulting products were yellow (GA pABA) and grayish white (GA BTA) powders. FTIR characterization confirmed the presence of imine stretching bands at 1640 to 1650 and the decrease of hydroxy and carbonyl intensities from GA1, indicating successful modification. The sonochemical method was efficient, energy saving, and capable of producing glucomannan derivatives with potential applications as green biopolymer based corrosion inhibitor precursors
