Search results for "X-ray crystal structures"

Conformational and structural studies of N-methylacetohydroxamic acid and of its mono- and bis-chelated uranium(VI) complexes

2015

The thermodynamics and kinetics of the cis/trans isomerism of N-methylacetohydroxamic acid (NMAH) and its conjugated base (NMA(-)) have been reinvestigated in aqueous media by (1)H NMR spectroscopy. Hindered rotation around the central C-N bond due to electronic delocalization becomes slow enough on the NMR time scale to observe both rotamers in equilibrium in D2O at room temperature. By properly assigning the methyl group resonances, evidence for the prevalence of the E over the Z form is unambiguously provided [K300=[E]/[Z]=2.86(2) and 9.63(5) for NMAH and NMA(-), respectively], closing thereby a long-lasting dispute about the most stable conformer. To that end, calculations of the chemic…