Journal of Chemical Physics, Vol.115, No.14, 6569-6577, 2001
H-bonding in amorphous acetamide CH3CONH2 as studied by x-ray scattering
Noncrystalline solid acetamide (CH3CONH2) can be prepared by vapor deposition onto precooled substrates at 77 K. The structure factor S-M(Q) derived from x-ray diffraction patterns is compared to that recently obtained for liquid acetamide near the melting point. The data are analyzed to yield the molecular structure factor F-1(Q) and the distinct pair correlation function g(L)(r). Our measurements clearly show that the hydrogen bonded network occurs in amorphous acetamide between C=O and N-H groups. Two H-bonds per molecule are found in average. The mean N . . .O distance is about 3.01 Angstrom. The results could be explained in terms of an open-chain structure which resembles preferentially the one existing in the metastable crystalline form. The crystallization of the glassy film which occurs on heating is also studied.