A Density Functional Theory Study on the Ring-Opening Polymerization of D-Lactide Catalyzed by a Bifunctional-Thiourea Catalyst

作者：Zhu Rong Xiu; Wang Ruo Xi; Zhang Dong Ju^*; Liu Cheng Bu

来源：Australian Journal of Chemistry, 2009, 62(2): 157-164.

DOI：10.1071/CH08118

The thiourea-catalyzed methanolysis of D-lactide, a model system for the initiation and propagation of the organocatalyzed ring-opening polymerization (ROP) of lactide, has been studied by performing density functional theory calculations. Both the catalyzed and uncatalyzed reactions are explored along two possible pathways: one involves the stepwise addition-elimination pathway and the other is related to the concerted pathway. It is found that the reaction without the presence of the catalyst is difficult because the barrier involved is as high as 176 kJ mol(-1). With the aid of a thiourea catalyst, the barrier is reduced to 88 kJ mol(-1) with a preference for the stepwise addition-elimination mechanism over the concerted one. The role of the catalyst has been rationalized by analyzing the frontier molecular orbital interactions between the catalyst and substrates and by performing natural population analysis. Finally, another mechanism involving acyl transfer is discussed for the thiourea-catalyzed ROP.

• 出版日期2009
• 单位山东警察学院; 山东大学