水液相环境下布洛芬分子手性对映体转变的机理

Mechanism of Chiral Enantiomer Transition of Ibuprofen Molecules in Water/Liquid Phase Environment

在SMD/MP2/6-311++g(3df,2pd)/WB97X-D/6-311++G(d,p)理论水平,对标题反应进行了研究.反应通道研究发现:质子直接迁移与2个水分子簇作质子迁移媒介时,布洛芬分子手性对映体转变都有2个反应通道a和b.a是α-氢只以羰基氧为桥迁移,b是羧基内质子迁移后α-氢再以新羰基氧为桥迁移.势能面计算表明:质子直接迁移,S-IBU在a和b通道实现手性对映体转变决速步骤的能垒分别是296.4和286.7kJ·mol-1,b通道具有优势.2个水分子簇作质子迁移媒介,S-IBU在a和b通道实现手性对映体转变决速步骤的能垒分别是163.2和160.5kJ·mol-1,b通道略微具有优势.结果表明:水液相环境下,水分子簇的催化可使布洛芬分子缓慢的实现手性对映体转变.

The title reaction was researched at the SMD/MP2/6-311++g(3 df,2 pd)/WB97 X-D/6-311++G(d,p)level of theory.The study of reaction channels showed that the chiral enantiomer transition of ibuprofen molecules all had two reaction channels a and b when protons were transported directly or with two water clusters as the transfer carrier.α-H was transferred only with the carbonyl oxygen as the bridge in channel a,and in channel b with the new carbonyl oxygen as the bridge after proton was transferred in carboxyl.The calculation of potential energy surface showed that when the protons was transferred directly,the energy barrier of the rate-determining step for S-IBU to realize chiral enantiomer transition in a and b channels were 296.4 and 286.7 kJ·mol-1,respectively,and the channel b had advantages.Accordingly,when two water clusters as the transfer carrier,the energy barrier were 163.2 and 160.5 kJ·mol-1,respectively,and the channel b had a slight advantages.The results showed that the catalysis of water clusters can make ibuprofen molecules realize chiral enantiomer transition slowly in water/liquid phase environment.