X-ray and vibrational studies of methyl (N-benzoylaminooxy)acetate

The crystal and molecular structures of methyl (N-benzoylaminooxy)acetate (MBAOA) have been determined by X-ray diffraction at room temperature. In the crystal the amide C=O of one molecule is hydrogen-bonded to the amide NH of an adjacent molecule (O1 ... N1' = 2.850(2) Angstrom, O1 ... H6'-N1' = 158(2)degrees). The ester C=O bond is cis oriented to the C-O (aminooxy) bond (the O2-C8-C0-O4 torsion angle is 2.6(3)degrees). IR and Raman spectra of MBAOA and its deuterated analogs have been measured in the solid state and in solution. In polar solvents the ester nu C=O was observed as a doublet feature in IR spectra, suggesting the existence of the two conformers having different torsion angles around the (O-)C-C(=O) bond. By combining the X-ray crystallographic result with the IR and Raman data, it is suggested that the conformer with the higher frequency of the ester nu C=O in solution has the ester C=O bond cis oriented to the C-O (aminooxy) bond.