Theoretical, structural, vibrational, NMR, and thermal evidence of the inter- versus intramolecular hydrogen bonding in oxamides and thiooxamides

This contribution describes the study of hydrogen bonding in secondary oxamides, monothiooxamides, and dithiooxamides by ab initio calculations, X-ray diffractions, NMR spectra, thermal analysis, and variable-temperature infrared and Raman spectroscopy. The results can all be interpreted as a function of the change in the strength and the nature of the hydrogen bonding by substituting oxygen for sulfur in the series CH3-HNCOCONHCH3, CH3HNCSCONHCH3, CH3HNCSCSNHCH3 and by changing the steric influence of the alkyl group in a series of oxamides (RHNCOCNHR; R = CH3, C2H5, iC(3)H(7), tC(4)H(9)).