Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

A series of 1-acylated and 1,3-diacylated (acyl = acetyl or benzoyl) ureas and thioureas have been prepared and their proton-coupled and proton-decoupled ¹⁵N, ¹³C, and ¹H NMR spectra have been measured. All the signals have been assigned. The ¹⁵N NMR chemical shifts in 1-acylated ureas and thioureas are shifted downfield as compared with δ(¹⁵N) of urea and thiourea, resp. This shift is greater for N-1 than for N-3 nitrogen atoms in both the series. When comparing acylureas and acylthioureas it is obvious from the Δδ(¹⁵N) differences that the CS group is better than CO group in transferring the electron-acceptor effect of acyl group. The proton-coupled ¹⁵N NMR spectra of the acylureas dissolved in hexadeuteriodimethyl sulphoxide exhibit a doublet of NH group and a triplet of NH₂ group at 25 °C. At the same conditions the acylthioureas exhibit a doublet of NH group, the NH₂ group signal being split into a doublet of doublets with different coupling constants ¹J(¹⁵N, H). The greater one of these coupling constants is due to the s-trans proton with respect to the sulfur atom of the thiourea.