N chemical shifts have been measured in some ureas and thioureas using double-irradiation techniques whilst observing the 1H n.m.r. spectra of the compounds. The values are compared with those obtained previously for amides, and the results indicate that the 14N chemical shift variations found in ureas and amides are governed by the degree of delocalisation of the nitrogen lone pair of electrons. The 14N chemical shift of selenourea is also recorded.
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Journal of the Chemical Society B: Physical Organic
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