Polymorphism of maleic hydrazide. I

Abstract

The third polymorph (denoted MH3) of maleic hydrazide (3,6-dihydroxypyridazine in the monolactim form, 6-hydroxy-3-pyridazinone, C4H4N2O2) has been studied by X-ray diffraction and shown to be monoclinic, space group P2(1)/n. Polymorph MH3 was found as the prevailing form along with the rare triclinic polymorph MH1, space group P1;, but they were obtained separately from monoclinic MH2, space group P2(1)/c. The structure of MH1, previously studied by photographic methods, has been redetermined. Polymorph MH3 exhibits the same scheme of molecular association into hydrogen-bonded ribbons as in MH1 and MH2, but the arrangements of the aggregates and details of their supramolecular conformations are different. The accommodation of the supramolecular conformations to the requirements of close packing of the aggregates in crystal lattices, as well as the symmetries of the polymorphs, are analyzed.

Effect of hydrostatic pressure on the crystal structure of sodium oxalate: X-ray diffraction study and ab initio simulations

“…So, the phase transition is an example of isosymmetric phase transitions, which were described previously also for other compounds [63][64][65][66][67]. Optical microscopy observations of a single crystal in the diamond anvil cell in the polarized light [13,68,69] were in an agreement with the fact that the symmetry of the crystal did not change in the course of the phase transition.…”

High-pressure diffraction studies of molecular organic solids. A personal view

“…Linear strain in the crystal structure does not always correlate with the changes in the interatomic distances in the hydrogen bonds in the same directions due to the conformational changes and rotation of molecules (Boldyreva, 1994(Boldyreva, , 2001(Boldyreva, , 2003a(Boldyreva, ,b, 2004a(Boldyreva, ,b,c, 2006Boldyreva et al, 1997aBoldyreva et al, ,b, 1998Boldyreva, Shakhtshneider et al, 2000;Katrusiak, 1996Katrusiak, , 2001Katrusiak, , 2003Katrusiak, , 2004a. Hydrogen bonds can be compressed but the structure expands and, vice versa, the structure can be compressed despite the expansion of the intermolecular hydrogen bonds.…”

A Theoretical Survey of Solvation Effects on Tautomerism Stability of Maleic Hydrazide

“…www.orientjchem.org Key words: Maleic hydrazide, Tautomer, PCM model, NBO Charge poly-morphs [13][14][15][16][17][18] and, in all the polymorphs, MH adopts exclusively the oxo-hydroxy form (Scheme 1). Tautomerism of solid maleic hydrazide was studied experimentally using infrared 19,20 and Raman spectroscopies.…”