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Methyl H Atoms (methyl + h_atom)
Selected AbstractsIn-situ high-pressure study of the ordered phase of ethyl propionateACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2007Roman Gajda Ethyl propionate, C5H10O2 (m.p. 199,K), has been in-situ pressure-frozen and its structure determined at 1.34, 1.98 and 2.45,GPa. The crystal structure of the new high-pressure phase (denoted ,) is different from phase , obtained by lowering the temperature. The freezing pressure of ethyl propionate at 296,K is 1.03,GPa. The molecule assumes an extended chain s-trans,trans,trans conformation, only slightly distorted from planarity. The closest intermolecular contacts in both phases are formed between carbonyl O and methyl H atoms; however, the ethyl-group H atoms in phase , form no contacts shorter than 2.58,Å. A considerable molecular volume difference of 24.2,Å3 between phases , and , can be rationalized in terms of degrees of freedom of molecules arranged into closely packed structures: the three degrees of freedom allowed for rearrangements of molecules confined to planar sheets in phase ,, but are not sufficient for obtaining a densely packed pattern. [source] Concomitant polymorphism and conformational isomerism in 4-acetylresorcinolACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2009Peter G. Jones Two polymorphs of the title compound [systematic name: 1-(2,4-dihydroxyphenyl)ethanone], C8H8O3, were investigated. The known structure [designated (I-M); P21/c, Z = 4; previously investigated at room temperature by Robert, Moore, Eichhorn & Rillema (2007). Acta Cryst. E63, o4252] was redetermined at low temperature, and a new form [(I-O); P212121, Z = 12] was discovered in the same sample. In both forms, the molecules are planar (apart from the methyl H atoms) and they contain intramolecular O,H...O=C hydrogen bonds. In polymorph (I-M), molecules are linked into chains by a single intermolecular O,H...O hydrogen bond, and the chains are linked into sheets by two C,H...O hydrogen bonds. Three O,H...O hydrogen bonds link the molecules of polymorph (I-O) into chains and neighbouring chains are connected by one C,H...O interaction to form an offset layer structure. Two weak methyl C,H...O interactions link the layers. [source] 3,5-Bis{3-[4-(dimethylamino)phenyl]prop-2-enylidene}-1-methyl-4-piperidone and 3,5-bis[3-(4-methoxyphenyl)prop-2-enylidene]-1-methyl-4-piperidone: potential biophotonic materialsACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2008Vladimir N. Nesterov The structures of the title compounds, C28H33N3O, (I), and C26H27NO3, (II), together with their two-photon absorption properties and fluorescence activities are reported. Molecules of (II) reside on crystallographic mirror planes containing the piperidone C=O group and N -methyl H atoms. Because of the conjugation between the donor and acceptor parts, the central heterocycle in both (I) and (II) exhibits a flattened boat conformation, with deviations of the N atom and the opposite C atom from the planar fragment. The dihedral angles between the coplanar heterocyclic atoms and terminal C6 rings are less than 20° in both (I) and (II). In (I), the N -methyl group of the ring occupies an equatorial position, but in (II) it is positioned in an axial site. In the crystal structure of (I), weak intermolecular C,H...,(arene) and C,H...O steric contacts link the molecules along the a axis. In the crystal structure of (II), molecules form stacks along the b axis. [source] Synthesis and Structural Characterization of 1,4-Di(2-methoxyphenyl)-2,5-piperazinedioneCHINESE JOURNAL OF CHEMISTRY, Issue 5 2007Shu-Sheng Zhang Abstract A new derivative of 2,5-piperazinedione, 1,4-di(2-methoxyphenyl)-2,5-piperazinedione (I), was synthesized by the cyclocondensation reaction of N -2-methoxyphenyl chloroacetamide, and its structure was characterized by elemental analysis, IR, 1H NMR and single crystal X-ray diffraction method. The crystal belongs to monoclinic system, space group P21/c with unit cell dimensions a=0.56934(10) nm, b=1.3880(2) nm, c=1.00329(17) nm, ,=90.376(3)°, V=0.7928(2) nm3, Z=2, Dc=1.367 g·cm,3, ,=0.98 cm,1, R and wR being 0.0606 and 0.1564 respectively for 1549 unique reflections with 1247 observed reflections [I>2,(I)]. The molecule has a crystallographically imposed symmetry center. The three rings in the molecule are each coplanar with their attached groups, excluding methyl H atoms and the H atoms attached to the piperazinedione ring, while the whole molecule is not planar, with dihedral angles of 74.7(1)° between the piperazinedione and each of the two aromatic rings. The crystal structure is stabilized by van der Waals and dipole-dipole forces. [source] | ||||||||||