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BETR法是通过CPMG脉冲系列消除手性位移试剂的宽峰,用~1H-NMR测定对映体含量的一个新而简单的方法。用此法测定了2′-羟基-2-苄氧基-1,1′联萘对映体含量,并发现随着手性位移试剂Eu(hfc)_3/联萘的克分子浓度比的增加,R异构体的亚甲基的二个质子共振峰向低场移动得比S异构体快,但S异构体的亚甲基的二个质子共振峰向低场移动的化学位移差值比R异构体增加快,并提出了由于Bloch-Siegert效应,它们的值都和磁场强度有关。
The BETR method is a new and simple method for the determination of the enantiomeric content by ~ 1H-NMR, using the CPMG pulse series to eliminate the broad peaks of chiral shift reagents. The enantiomer content of 2’-hydroxy-2-benzyloxy-1,1’-binaphthyl was determined by this method. It was found that with the increase of the molar concentration ratio of Eu (hfc) The two proton resonances of the methylene group of R isomers move toward the lower field faster than that of the S isomer but the chemical shifts of the two proton resonances of the S isomer move toward the lower field Increase faster than the R isomer and propose that due to the Bloch-Siegert effect, their values are related to the magnetic field strength.