羧甲基壳聚糖衍生物及其振动光谱的理论研究

用量子化学从头算STO 3G法研究了羧甲基壳聚糖及其衍生物的结构和稳定性，计算结果表明:1)壳聚糖单体经羧甲基化后，得到2种可能的产物，其中羧甲基在壳聚糖单体2位氨基上的取代产物较6位羟基上的取代产物稳定； 2)以羧甲基壳聚糖为母体经加成反应，得到羧甲基壳聚糖衍生物（2 羟基 3 丁氧基）丙基 羧甲基壳聚糖的2个异构体， 其中构型1更稳定.在优化构型的基础上，计算所得的构型1的振动光谱与实验结果相吻合.

Theoretical Studies on the Structures and the Vibration Spectra of Carboxymethylchitosan and Its Derivatives

The structures and stabilities of carboxymethylchitosan and its derivatives were studied by using quantum chemical ab initio method. The calculated results indicated that the structure of carboxymethylchitosan in which the 2 site amino group of chitose(see Fig.2) was substituted by ethyloic was more stable than that in which 6 site hydroxyl group was substituted(see Fig.3). Between two isomers of carboxymethylchitosan deriva tives(i.e.(2 hydroxyl 3 butoxyl)propyl carboxymethylchitosan, see Fig.4), isomer 1 was more stable than isomer 2. By using the optimized geometries, the vibration spectra of isomer 1 was calculated. And it was in good agreement with recent experimental results.