Configurational Assignment of Long-Chain Alkylated Pyridinium Aldoxime Bromides by Noesy Experiments
作者:Mamta Sharma、A.K. Gupta、S.K. Raza
DOI:10.3184/030823408x318424
日期:2008.5
A configurational study of long-chain N-alkylated pyridinium aldoxime derivatives and their positional isomers has been carried out by two-dimensional 1H-1H NOESY (nuclear Overhauser effect spectroscopy). Cross peak intensities were observed to be enhanced with increasing mixing time. Mixing times longer than 250 ms result in increasing contribution of spin diffusion that produces unrealistic hydrogen-hydrogen
长链 N-烷基化吡啶鎓醛肟衍生物及其位置异构体的构型研究已通过二维 1H-1H NOESY(核 Overhauser 效应光谱)进行。观察到交叉峰强度随着混合时间的增加而增强。混合时间超过 250 毫秒会导致自旋扩散的贡献增加,从而产生不切实际的氢-氢距离。NOE 测量结果表明,照射羟基质子共振时亚胺基质子共振的强度显着增强,反之亦然。发现羟基质子共振和亚胺基质子共振之间的化学位移差异对于顺构型为~4 ppm,对于反构型为~5 ppm。研究表明,这些化合物以 E 构型存在,即溶液中的顺式。顺式异构体占优势;反异构体的量为3%(2-肟)、4%(3-肟)和6%(4-肟)。