A neutron diffraction study of α-oxalic acid dihydrate

Structure of potassium tris(oxalato)manganate(III) trihydrate

“…The -C-C(=O)-Ogroups are planar and twist angles as defined by Siems & Lohn (1972) range from 6.0 to 7.4 °. The C-C lengths are comparable to those found in oxalic acid dihydrate (Sabine & Cox, 1969), [Mn(C204)]. 2H20 (Deyrieux, Berro & Peneloux, 1973) and Cs2[Mn2(C2Oa)3].3H20 (Siems & Lohn, 1972).…”

“…1. The geometry of the ligands shows no extraordinary deviations from the known examples, neutron diffraction results for free oxalic acid (Sabine & Cox, 1969) There is no clear difference (in the limits of 3a) between the bonds C-O(endocyclic) (single-numbered O atoms in Table 2) and C-O(exocyclic) (double-numbered O atoms in Table 2). The oxalate ligands are not planar.…”

The dislocation arrangement in α-oxalic acid dihydrate

“…Thus it is to be expected that extinction will be anisotropic in oxalic acid dihydrate since the perfection of the crystal to X-rays will be a function of orientation. This is consistent with the work of Sabine, Cox & Craven (1969) who observed anisotropic extinction in c~-oxalic acid dihydrate and suggested that the layers of atoms appeared rumpled in the ae plane but showed little rotation about the b axis.…”

“…Recent crystal structure investigations with X-rays and neutrons (Coppens, 1967;Sabine, Cox & Craven, 1969;Coppens & Sabine, 1969;Delaplane & Ibers, 1969) have had as their objective the determination of physically meaningful thermal parameters from which a determination of the asphericity of electron distribution around an atom in a crystal may be obtained. Since the calculations of X-ray structure factors are carried out for spherical atoms, and since the asphericity results from a distortion of the electron distribution along a chemical bond, the apparent X-ray temperature factor is increased.…”

Configuration of the ring A methoxyl in delphinine and aconitine from the crystal structure of a synthetic intermediate, C22H30O5N.C2HO4

“…There is also a reason- [e.g. 1.569(8)A in ammonium oxalate; Robertson, 1965], but significantly longer than 1.536(3)A, which was observed in a-oxalic acid (Sabine, Cox & Craven, 1969). The C(24)-~O(8) bond is significantly shorter [by 0-024(4)A] than C(24)=-=O(7).…”