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A Katrusiak

Publications and source records attributed to A Katrusiak.

10 recordsLinked to original sources
PubMed2001

Polymorphism of maleic hydrazide. I.

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.

Journal Article↗
PubMed2001

Crystallographic autostereograms.

Perspective drawings of crystal structures can be presented as autostereograms (or single-image stereograms), and their performance for in-depth perception is similar or even more advantageous than of stereopairs. The autostereograms offer a convenient means for realistic insight into crystal structures without excessive size reduction of their drawings, as required when preparing stereopairs; thus structures either as simple as elements or as complex as proteins can be illustrated in enhanced resolution. The mathematical background and guidelines for preparing crystallographic autostereograms are described.

Computer Graphics↗
PubMed2000

Conformational transformation coupled with the order-disorder phase transition in 2-methyl-1,3-cyclohexanedione crystals.

The half-chair conformation of the dynamically disordered molecular ring of 2-methyl-1,3-cyclohexanedione, C(7)H(10)O(2), transforms to a sofa below Tc = 244 K, when the crystal undergoes a continuous phase transition induced by the onset of halting large-amplitude vibrations of methylene groups C(4)H(2) and C(5)H(2). The temperature dependence of the crystal structure has been investigated by X-ray diffraction. The Ibam symmetry of the crystal reduces below Tc to space group Pccn. The mechanism of the phase transition and of the conversion of the ring conformation is discussed.

Journal Article↗
PubMed2000

Designing large triangular chiral macrocycles: efficient

Triangular 30- and 27-membered hexaiminomacrocycles 4 and 5 of D(3) and C(3) symmetry, respectively, are readily obtained by unprecedented [3 + 3] cyclocondensation of (R,R)-1, 2-diaminocyclohexane with, accordingly, terephthalaldehyde and isophthalaldehyde. The course of the reaction, leading to macrocyclization, is governed by conformational constraints imposed on the structural components of the intermediate products, as shown by molecular modeling. X-ray analysis of cocrystal 4.AcOEt revealed that the macrocycle symmetry significantly departs from ideal D(3) symmetry due to crystal environment. Cyclic hexaamines 6 and 7 were prepared by sodium borohydride reduction of 4 and 5, respectively.

Journal Article↗
PubMed1989

Structure of 6-amino-4,4,5,7,8-pentamethyldihydrocoumarin.

C14H19NO2, Mr = 233.3, triclinic, P1, a = 9.925 (2), b = 11.193 (3), c = 11.915 (3) A, alpha = 95.39 (2), beta = 91.09 (2), gamma = 97.38 (2) degrees, V = 1304.7 (3) A3, Z = 4, F(000) = 480, Dx = 1.19 (1), Dm = 1.18 (1) g cm-3, lambda(Mo K alpha) = 0.71069 A, mu(Mo K alpha) = 0.43 cm-1, T = 292 K. Final R = 0.045 for 3099 observed reflections. The statistically significant difference in bond length C(6)-N between the two independent molecules can be explained in terms of the differences in the intermolecular interactions of the N atoms. The conformation of the lactone ring in both independent molecules is intermediate between half-chair and sofa and very similar to that observed in 4,4,5,7,8-pentamethyldihydrocoumarin. In both these compounds similar large distortions of valency angles occur in the phenyl rings to accommodate the overmethylation.

Chemical Phenomena↗
PubMedDate not supplied

Triazolo- and tetrazolopyridazine derivatives and their hypotension and heart rate activity.

6-Chloro-, 6-morpholino- and 6-N-methylpiperazino-1,2,4-triazolo[4,3-b]- or 1,2,3,4-tetrazolo[1,5-b]pyridazines [II-VII] were synthesized from 3-chloro-6-hydrazinopyridazine [I]. Positive effect of a series of tetra- and triazolopyridazines for lowering blood-pressure without affecting the heart rate was found in tests on rats. Their lipophilicity and other properties are discussed.

Animals↗