Urea and phosphoric acid form an adduct (UPA) in which a strong hydrogen bond is formed involving the hydrogen atom of the acid and the carbonyl oxygen of the urea. Previous studies have shown that at low temperatures this proton is localised on the urea molecule, but as temperature increases the proton migrates to a position midway between the two O atoms. We aimed to explore the effect on this migration phenomenon of replacing hydrogen for deuterium, especially as computational studies had suggested that coupling of vibrational modes may be important. Experiments performed on SXD and HIPR for perdeuterated-UPA showed migration of deuterium towards urea with either decreasing temperature or increasing pressure.
CK Spanswick , CA Morrison, CR Pulham (University of Edinburgh), DS Middlemiss, A Parkin, CC Wilson (University of Glasgow), MJ Gutmann, WG Marshall (ISIS)
Research date: December 2006
Dr CR Pulham, [CRPulham@ed.ac.uk] CA Morrison et al., J. Am. Chem. Soc. 127 (2005) 4042