256 research outputs found

    Ferroelastic phases and order parameter treatment in Pb 3

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    2,3,4,6-Tetra-O-benzoyl-4-nitro­phenyl-1-thio-α-d-mannopyran­oside–dichloro­methane–diethyl ether mixed solvate (1/0.53/0.38)

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    The title compound, C40H31NO11S·0.53CH2Cl2·0.38C4H10O, was synthesized in two steps from mannose penta­acetate and single crystals were grown by slow evaporation. The structure was determined by single-crystal X-ray diffraction, confirming the α-configuration of the anomeric thioaryl substituent. The asymmetric unit contains two crystallographically distinct mol­ecules of the carbohydrate. The central pyran­ose rings of these are geometrically similar, but there are differences in the orientations of the benzoate substituents

    8-Chloro-5,5-dimethyl-5,6-dihydro­tetra­zolo[1,5-c]quinazoline

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    In the title compound, C10H10ClN5, the tetra­zole ring and the phenyl ring make a dihedral angle of 7.7 (2)°. The hexa­hydro­pyrimidine ring adopts a screw-boat conformation. In the crystal, inter­molecular bifurcated N—H⋯(N,N) hydrogen bonds link the mol­ecules into [001] chains

    (2E,4E)-1-(6-Chloro-2-methyl-4-phenyl-3-quinol­yl)-5-phenyl­penta-2,4-dien-1-one

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    In the title compound, C27H20ClNO, the quinoline ring forms a dihedral angle of 62.53 (5)° with the substituent benzene ring. In the crystal, inter­molecular C—H⋯Cl inter­actions link the mol­ecules into chains along the b axis. Inter­molecular C—H⋯N and C—H⋯O hydrogen bonds further consolidate the structure into a three-dimensional network. The unit cell contains four solvent-accessible voids, each with a volume of 35 Å3, but no significant electron density was found in them

    N-Benzyl-1,3-dide­oxy-1,3-imino-l-xylitol

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    The structure determination confirms the stereochemistry of the title compound, C12H17NO3, which contains a four-membered azetidine ring system. The absolute configuration was determined by the use of d-glucose as the starting material. In the crystal, O—H⋯O and O—H⋯N hydrogen bonds link the mol­ecules into layers in the ab plane

    4-Methoxy­phenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-d-mannopyran­oside

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    The title compound, C21H26O10S, was synthesized in a single step from mannose penta­acetate. The mol­ecular structure confirms the α configuration of the anomeric thioaryl substituent. Spectroscopic and melting-point data obtained for the title compound are in disagreement with those previously reported, indicating the previously reported synthesis [Durette & Shen (1980 ▶). Carbohydr. Res. 81, 261–274] to be erroneous. The crystal structure is stabilized by weak inter­molecular C—H⋯O hydrogen bonds

    Investigation of high-pressure planetary ices by cryo-recovery. I. An apparatus for X-ray powder diffraction from 40 to 315 K, allowing 'cold loading' of samples

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    A low-temperature stage for X-ray powder diffraction in Bragg–Brentano reflection geometry is described. The temperature range covered is 40–315 K, with a temperature stability at the sample within +-0.1 K of the set point. The stage operates by means of a Gifford–McMahon (GM) closed-cycle He refrigerator; it requires no refrigerants and so can run for an extended period (in practice at least 5 d) without intervention by the user. The sample is cooled both by thermal conduction through the metal sample holder and by the presence of He exchange gas, at ambient pressure, within the sample chamber; the consumption of He gas is extremely low, being only 0.1 l min-1 during normal operation. Aunique feature of this cold stage is that samples may be introduced into (and removed from) the stage at any temperature in the range 80–300 K, and thus materials which are not stable at room temperature, such as highpressure phases that are recoverable to ambient pressure after quenching to liquid nitrogen temperatures, can be readily examined. A further advantage of this arrangement is that, by enabling the use of pre-cooled samples, it greatly reduces the turnaround time when making measurements on a series of specimens at low temperature

    2- N

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