Structural studies of oxalohydroxamic acid by single crystal X-ray diffraction and spectroscopic methods

Abstract

The structure of oxalohydroxamic acid has been investigated by X-ray and spectroscopic analyses. It has been shown that oxalohydroxamic acid exists in the oxamic form in the solid as well as in solution. The variable-temperature nuclear magnetic resonance (NMR) studies reveal an exchange of OH and NH protons, the exchange being faster at higher temperatures. The kinetic and the thermodynamic parameters such as the rate constant (K), the free energy of activation $(\Delta G^{\ddagger})$, and the energy of activation $(E_a)$ for the exchange process have been obtained. The compound crystallizes in the monoclinic space group $P2_1/c$ with a=5.208, b=3.864, $c=11.482 \AA$ ,$\beta = 111.45^0$, and Z=2. The structure was solved with MULTAN 80. The refinement by block diagonal least squares and Fourier methods provided R=0.035. There is strong hydrogen bonding between the molecules which form dimer