1H and 13C NMR spectra of some unsymmetric N,N′-dipyridyl ureas: spectral assignments and molecular conformation
作者:Netai C. Singha、Dixit N. Sathyanarayana
DOI:10.1039/a606800f
日期:——
The 1H NMR spectra of N-(2-pyridyl),
Nâ²-(3-pyridyl)ureas and N-(2-pyridyl),
Nâ²-(4-pyridyl)ureas in CDCl3 and
(CD3)2CO have been assigned with the aid of COSY and
NOE experiments and chemical shift and coupling constant correlations. The
13C NMR spectra in CDCl3 were analysed utilizing the
HETCOR and proton coupled spectra. The 1H NMR spectra, NOE
effects and MINDO/3 calculations have been utilized to show that the
molecular conformation of these compounds has the 2-pyridyl ring coplanar
with the urea plane with the NâH group hydrogen bonded to the
nitrogen of the 2-pyridyl group on the other urea nitrogen while the
3/4-pyridyl group rotates rapidly about the
NâC3/NâC4 bond.
借助 COSY 和 NOE 实验以及化学位移和耦合常数相关性,分配了 N-(2-吡啶基)、Nâ²-(3-吡啶基)脲和 N-(2-吡啶基)、Nâ²-(4-吡啶基)脲在 CDCl3 和 (CD3)2CO 中的 1H NMR 光谱。利用 HETCOR 和质子耦合光谱分析了 CDCl3 中的 13C NMR 光谱。利用 1H NMR 光谱、NOE 效应和 MINDO/3 计算表明,这些化合物的分子构象是 2-吡啶基环与脲平面共面,NâH 基氢键与另一个脲氮上的 2-吡啶基氮相连,而 3/4 吡啶基围绕 NâC3/NâC4 键快速旋转。