1H and 13C NMR spectra of some unsymmetric N,N′-dipyridyl ureas: spectral assignments and molecular conformation
- 1 January 1997
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 2,p. 157-162
- https://doi.org/10.1039/a606800f
Abstract
The 1H NMR spectra of N-(2-pyridyl), N′-(3-pyridyl)ureas and N-(2-pyridyl), N′-(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 N–H 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 N–C3/N–C4 bond.Keywords
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