Kinetics of de-N-acetylation of the chitin disaccharide in aqueous sodium hydroxide solution

详细信息	查看全文 | 推荐本文 |

• 作者：Thang Trung Khong^a ; ^b ; Finn L. Aachmann^a ; Kjell M. Vå ; rum^a ; ^{Kjell.Morten.Vaarum@biotech.ntnu.no}
• 关键词：Chitin oligomer ; Chitosan ; Deacetylation ; Reaction rate
• 刊名：Carbohydrate Research
• 出版年：2012
• 期刊代码：15_00086215
• 类别：ch
• 出版时间：1 May, 2012
• 卷：352
• 期：Complete
• 页码：82-87
• 文件大小：1153 K

摘要

Chitosan is prepared from chitin, a process which is carried out at highly alkaline conditions, and that can be performed either on chitin in solution (homogeneous deacetylation) or heterogeneously with the chitin as a solid throughout the reaction. We report here a study of the de-N-acetylation reaction of the chitin dimer (GlcNAc-GlcNAc) in solution. The reaction was followed by ¹H NMR spectroscopy in deuterated aqueous sodium hydroxide solution as a function of time, sodium-hydroxide concentration and temperature. The ¹H NMR spectrum of GlcNAc-GlcNAc in 2.77 M deuterated aqueous sodium hydroxide solution was assigned. The interpretation of the ¹H NMR spectra allowed us to determine the rates of de-N-acetylation of the reducing and non-reducing ends, showing that the reaction rate at the reducing end is twice the rate at the non-reducing end. The total deacetylation reaction rate was determined as a function of the hydroxide ion concentration, showing for the first time that this de-N-acetylation reaction is second order with respect to hydroxide ion concentration. No significant difference in the deacetylation rates in deuterated water compared to water was observed. The activation energy for the reaction (26-54 掳C) was determined to 114.4 and 98.6 kJ/mol at 2.77 and 5.5 M in deuterated aqueous sodium hydroxide solution, respectively.