Conformation of some biologically active aromatic ureas |
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Authors: | Hadjieva Boriana Ilieva Sonia Cheshmedzhieva Diana Galabov Boris |
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Affiliation: | Department of Chemistry, University of Sofia, 1 James Bourchier Avenue, 1164 Sofia, Bulgaria. |
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Abstract: | Experimental IR spectroscopic data for the N-H stretching mode frequencies for several types of tri-substituted ureas containing benzyl and/or phenyl substituents as well as theoretical results from B3LYP/6-31G(d,p) computations on selected compounds provide sufficient evidence to determine the conformational state of these molecules. Two types of N-H bands may be found the spectra: (a) A type band due to a classical trans conformation (trans I) of the CONH structure; (b) B type band arising from an alternative trans form (trans II), in which the N-H band is involved in a hydrogen bond like interaction with the aromatic ring at the neighbouring nitrogen atom (benzyl or phenyl substituents). The N-H band of trans ICONH structure is observed at frequencies higher than 3460 cm-1, the actual position depending on weather the non-substituted N-H group is linked to aryl or alkyl substituents. The N-H band of the trans II rotameric structure is observed at 3430-3420 cm-1. |
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