Intramolecular Hydrogen Bonding in Guanidinium and Potassium Hydrogen Malonates - an Infrared and X-Ray Diffraction Study

A new modification of potassium hydrogen malonate was obtained by crystallization from dimethylsulphoxide (DMSO)\u27 solution. Its infrared spectrum differs in its essential features from the spectra of the known modification crystallizing from water!-" but resemble those of guanidinium hydrogen malonate. Both spectra are interpreted in terms of strong, intramolecular hydrogen bonding, This is supported by the fact that the main features (CO and OH stretching) remain essentially unchanged on dissolution in DMSO and by the X-ray diffraction on guanidinium hydrogen malonate. The structure of its crystals was solved by the direct method and refined by full matrix least squares to R value of 0.044 for 453 observed reflections. The structure consists of planar guanidinium ions and hydrogen maleate residues containing short intramolecular, but asymmetric bonds of 2.407(3)A

The Crystal and Molecular Structure of 3-(Pyridyl-2\u27)- imidazo-[1,i-a] Pyridine

The crystal structure of 3:.(pyridyl-2\u27)-imidazo-[l,5-a] pyridine has been determined using three-dimensional MoK a diffractometer data. The crystal data at 293 (1) K are as follows: C12H0Na, Mr= = 195.23, orthorhombic, P212121 (No. 19), a = 0.5107(1), b = 1.3076(2}, c = 1.4343(3) nm, V = 0.9578 nm3, Dm = 1.37(5), Dx = 1.354 Mg · m-3, Z = 4. The structure has been solved with direct methods and refined by full-matrix least-squares techniques to R and Rw values of 0.085 and 0.080, respectively, for 641 contributing reflexions. The crystal structure consists of discrete molecules. Most of the bond lengths and angles are within normal ranges for aromatic heterocyclic systems. The dihedral angle between the pyridine and imidazo- pyridine parts of the molecule is 3.8°; thus the molecule is planar to within 7 pm owing to two weak C-H .. . N interactions

The Crystal and Molecular Structure of 3-(Pyridyl-2\u27)- imidazo-[1,i-a] Pyridine

The crystal structure of 3:.(pyridyl-2\u27)-imidazo-[l,5-a] pyridine has been determined using three-dimensional MoK a diffractometer data. The crystal data at 293 (1) K are as follows: C12H0Na, Mr= = 195.23, orthorhombic, P212121 (No. 19), a = 0.5107(1), b = 1.3076(2}, c = 1.4343(3) nm, V = 0.9578 nm3, Dm = 1.37(5), Dx = 1.354 Mg · m-3, Z = 4. The structure has been solved with direct methods and refined by full-matrix least-squares techniques to R and Rw values of 0.085 and 0.080, respectively, for 641 contributing reflexions. The crystal structure consists of discrete molecules. Most of the bond lengths and angles are within normal ranges for aromatic heterocyclic systems. The dihedral angle between the pyridine and imidazo- pyridine parts of the molecule is 3.8°; thus the molecule is planar to within 7 pm owing to two weak C-H .. . N interactions