Hydrogen bond studies. CXXII. A neutron diffraction and X–N deformation-electron-density study of dimethylammonium hydrogen oxalate, (CH₃)₂NH₂HC₂O₄, at 298 K

A deformation electron density study of potassium oxalate monohydrate at 100 K

“…The C-C bond length found in a-H2C2Oa.2H20 by X-ray diffraction at 100 K (Stevens & Coppens, 1980;Wang, Tsai, Liu & Calvert, 1985) and neutron diffraction at 100 K (Feld & Lehmann, 1979) is 1-544(1), 1.545 and 1.544 (1)/~, respectively. The C-C bond length in (CH3)2NH2HC204 obtained from X-ray and neutron diffraction at room temperature (Thomas, 1977) is 1.545 (2) and 1.548 (2) A; in NaHC204.H20, obtained by neutron diffraction at room temperature (Tellgren, Thomas & Olovsson, 1977) and at 120 K (Delaplane, Tellgren & Olovsson, 1984) it is 1.552 (1) and 1.553 (1) A, respectively. In ammonium oxalate monohydrate studied by X-ray and neutron diffraction at room temperature (Taylor & Sabine, 1972), the fully ionized C20 2-groups have C-C distances of 1.565 (14) and 1.557 (2)A.…”

“…The present work forms part of a series of electron density studies of systems involving oxalate groups: (CH3)ENHEHC204 (Thomas, 1977), NaHCEO4.H20 (Tellgren, Thomas & Olovsson, 1977;Delaplane, Tellgren & Olovsson, i987). In combination with earlier extensive studies of ot-H2C204.2H20 (Stevens & Coppens, 1980;Stevens, 1980;Dam, Harkema & Feil, 1983;Wang, Tsai, Liu & Calvert, 1985), this makes it possible to compare the electron density features in C2H204, C2HO4 and C20 2-groups.…”

X-ray study of structure and charge density of 1-methylsulfonyl-2-phenylsulfonylethane

“…Cochran, 1953;Hanson, Sieker & Jensen, 1973;Kvick, 1974) the positional parameters of bonded H atoms from conventional X-ray least-squares refinement are systematically affected by the strong asphericity of the electron density near H. Combined X-ray and neutron diffraction studies have shown that the X-ray shift of the charge centroid relative to the nuclear position is along the X-H vector. The effect is shortening but not, as a rule, any significant angular distortion at this bond (Kvick, 1974;Thomas, 1977). Thus, in the absence of unbiased parameters for H a reliable and significant correction for the X-ray shortening of X-H lengths can be applied.…”

Structure of dimethylammonium N,N,N',N'-tetramethylformamidinium hexachlorotellurate(IV)

“…In addition, the longest Tc C1 distances, 2.570 (2) and 2.618 (2),A,, are found between Te and those CI atoms that are nearest to the cations. The cation (CH3)2NH2 + has been observed in many structures such as that determined from the X-ray and neutron diffraction studies of dimethylammonium hydrogen oxalate at 298 K by Thomas & Pramatus (1975) and Thomas (1977). Compared to these studies the present structure shows a considerable shortening of the C--N bonds from 1.47 to 1.44/~.…”