Ab initio computational study of _N-C and _O-C bonding formation : functional group modification reaction based chitosan

12th Joint Conference on Chemistry

Siahaan, P.^1 ; Salimah, S.N.M.^1 ; Sipangkar, M.J.^1 ; Hudiyanti, D.^1 ; Djunaidi, M.C.^1 ; Laksitorini, M.D.^2

Department of Chemistry, Diponegoro University, Semarang, Indonesia^1

Department of Pharmaceutics, Faculty of Pharmacy, Gadjah Mada University, Sekip Utara, Yogjakarta, Indonesia^2

关键词: Ab initio;    Basis sets;    Carboxyl groups;    Carboxymethyl chitosan;    Computational approach;    Computational studies;    Modification reactions;    Reaction mechanism;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/349/1/012049/pdf
DOI  :  10.1088/1757-899X/349/1/012049

来源: IOP

【 摘 要 】

Chitosan application in pharmaceutics and cosmeceutics industries is limited by its solubility issue. Modification of -NH2and -OH fuctional groups of chitosan by adding carboxyl group has been shown to improve its solubility and application. Attempt to synthesize carboxymethyl chitosan (CMC) from monocloroacetic acid (MCAA) has been done prior this report. However no information is available wether -OH (-O-C bonding formation) or -NH2(-N-C bonding formation) is the preference for - CH2COOH to attach. In the current study, the reaction mechanism between chitosan and MCAA reactants into carboxymethyl chitosan (CMC) was examined by computational approach. Dimer from of chitosan used as a molecular model in calculation All the molecular structure involved in the reaction mechanism was optimized by ab initio computational on the theory and basis set HF/6-31G(d,p). The results showed that the - N-C bonding formation via SN2 than the -O-C bonding formation via SN2 which have activation energy 469.437 kJ/mol and 533.219 kJ/mol respectively. However, the -O-C bonding formation more spontaneous than the -N-C bonding formation because ΔG the formation of O-CMC-2 reaction is more negative than ΔG of formation N-CMC-2 reaction is -4.353 kJ/mol and -1.095 kJ/mol respectively. The synthesis of N,O-CMC first forms -O-CH2COOH, then continues to form -NH-CH2COOH. This information is valuable to further optimize the reaction codition for CMC synthesis.