Crystal and molecular structure of o-methacryloylaminophenylarsonic acid

The title compound, o-methacryloylaminophenylarsonic acid (o-MAPHA), C₁₀H₁₂AsNO₄, is a monomer used to obtain water-soluble polyelectrolytes. It was obtained from the condensation reaction of o-arsanilic acid and methacryloyl chloride. Crystallization from aqueous ethanol solution yielded colorless prismatic crystals, and one was used for X-ray analysis. The crystal structure was solved using direct methods with a refined R ₁ = 0.0483. The crystal structure belongs to the triclinic system, space group , and the asymmetric unit comprises two molecules of the o-MAPHA acid and one water molecule. Both acid molecules are approximately planar and in both molecules the As atom presents common tetrahedral geometry with two long As–O bonds for hydroxyl groups and one short As–O bond for the oxo groups. The structure of o-arsanilic acid (o-ARSA), C₆H₈AsNO₃, was also determinated using the same methods and compared with the o-arsanilic acid structure previously reported. The crystal structure of the o-arsanilic acid belongs to the monoclinic crystal system and to the P2₁ noncentrosymmetric space group with Z equals two.     

Crystal- and molecular structure of 19-nor-digitoxigenin

19-nor-Digitoxigenin crystallizes in the orthorhombic space group P 2₁2₁2₁ with four formula units C₂₂H₃₂O₄ per unit cell. The lattice parameters are a = 7.082, b = 12.476, c = 21.486 Å. The crystal structure was determined by direct methods and refined by a least-squares procedure to the discrepancy factor R = 0.042. — The orientation of the lactone ring relative to the steroid skeleton was found to be the opposite of that known for digitoxigenin.     

Electrical Conductivity in TCNQ Salts of Bis(4-dimethylaminophenylimino) sulfur and its Structural Analogues

Four compounds, N,N,N',N'-tetramethyl-p-phenylene diamine, N,N,N',N'-tetramethyl-benzidine, 4,4'-bis(dimethylamino)azobenzene and bis(4-dimethylaminophenylimino)sulfur (BAPIS) were examined electrochemically and spectroscopically. Each was shown to be a fairly good donor forming in its first oxidation state a radical-cation. The latter two materials surprisingly exhibited only single one-electron oxidations. Conformational flexibility about the -NSN- unit was studied by NMR spectroscopy and ab initio molecular orbital theory. The experimental ΔG* for a cis-trans to trans-cis interconversion in BAPIS was found to be 11.9 kcal/mole.

The four donors all form 1:1 adducts with TCNQ. The compaction resistances of the complexes have been measured as a function of temperature. Of the four, (BAPIS)(TCNQ) appears to be a one-dimensional material. The other three complexes behave as typical mixed stack organic semiconductors.     

Crystal and molecular structure of anhydroerythromycinA cyclic carbonateN-methyl iodide

The crystal and molecular structure of C₃₉H₆₆INO₁₃ · CH₃OH has been determined by single-crystal x-ray diffraction analysis. The compound crystallizes in the monoclinic space, groupP2₁, witha =14.35(1),b=14.38(1),c =10.91(1) Å, = 96.10(5) °, andZ = 2. Three-dimensional intensity data were collected on a four-circle fully automated diffractometer. The structure was solved by the heavy-atom method. The positions of all atoms have been refined by block-diagonal and full-matrix least squares, using anisotropic temperature factors. The finalR value was 0.109 for 2194 independent reflections. The analysis does not confirm the hypothetical structure proposed by the Eli Lilly group, as far as a position of a cyclic carbonate moiety is concerned. They postulated that the cyclic carbonate moiety was attached to C(9) and C(11) of the erythronolide. The results obtained by us show that the cyclic carbonate moiety is attached to C(11) and C(12). The absolute configuration of the asymmetric centers agrees fully with that established for erythromycinA.     

Further conformational aspects of the amino-acid histidine: crystal and molecular structure of histidine dihydrochloride

Histidine dihydrochloride crystallizes in the orthorhombic system, space groupP2₁2₁2₁, with unit-cell dataa = 6.970(4),b = 16.165(7),c = 8.964(6)Å,V _c = 1010.0ų andZ = 4. Intensities for 1360 independent reflections were collected on an automated diffractometer. The structure was solved by standard heavy-atom methods and refined by full-matrix least squares, based onF, to anR-value of 0.027. The final weightedR-value and goodness-of-fit are 0.029 and 1.9, respectively. The histidine residue exists in the crystal as the carboxylic acid with protonation of the primary amine nitrogen and the imidazole ring. The overall conformation of the molecule is extended, similar to that observed inL-histidine,DL-histidine hydrochloride dihydrate, and one of the two independent molecules in the structure ofL-N-acetylhistidine. There is an extensive array of hydrogen bonds formed in the crystal, which, presumedly, together with the observed electrostatic interactions, account for the adopted molecular conformation.This investigation was supported by the donors of the Petroleum Research Fund, administered by the Americal Chemical Society, and by a National Institutes of Health Biomedical Science Support Grant. The diffraction equipment was purchased through a grant from the National Science Foundation.     

Investigation of nucleation kinetics and crystal defects of HMX

The nucleation kinetics of HMX (cyclotetramethylene tetranitramine, C₄H₈N₈O₈) in γ‐butyrolactone was studied in cooling process by induction time method. The laser scattering method was used to measure the solubility data and metastable region of HMX in γ‐butyrolactone. The induction time was measured over a range of supersaturation at different temperatures. Then, the nucleation mechanism of HMX in γ‐butyrolactone was investigated by analysis the relationships between induction time and supersaturation. The results indicated homogeneous nucleation dominated at high supersaturation of S >1.35, while the heterogeneous nucleation dominated at low supersaturation of S < 1.35. The values of interfacial tension at different final temperatures were calculated to indicate the ability of HMX to be crystallized. The growth mechanism of HMX was investigated by the data fitting applying different growth mechanism models and identified as two‐dimensional nucleation‐mediated (2D) growth. Finally, the effects of supersaturation and temperature on the crystal defects were analyzed based on the nucleation kinetics. When the temperature is below 303.15K, homogeneous nucleation dominated the nucleation process at higher supersaturation. Fine HMX crystals with more defects were produced. On the contrary, heterogeneous nucleation mechanism dominated at lower supersaturation. large regular HMX crystals with fewer defects were formed when the temperature is above 318.15K.     

Investigation of Ultrasonic Velocity and Related Parameters in Liquid Crystalline Mixtures

Investigations of ultrasonic velocity, specific volume and related parameters were carried out in a mixture of p-n-butoxybenzylidene-p-chloroaniline (BBCA) and p-anisal-p-toluidine (pApT) at eight different concentrations. BBCA exhibits polymorphism with two smectic phases, viz., smectic B and smectic A, while pApT is non-mesomorphic. All the mixtures studied were nematic, the mesomorphism vanishes below 34.3 mole percent of BBCA. Specific volume showed a large increase in the vicinity of the phase transition and the ultrasonic velocity showed an abrupt minimum near the transition. The adiabatic compressibility showed a maximum near the phase transition. It was found that the dip in ultrasonic velocity, change in specific volume and the jump in adiabatic compressibility at the transition decreases with increasing concentration of the non-mesomorphic compound. The parameter, viz., molar sound velocity was also estimated. The coefficient of thermal expansion and adiabatic compressibility were also estimated and they were found to attain very high values near the phase transition. The experimental results are explained on the basis of de Gennes theory of pre-transitional effects generalized by Bendler. The critical exponents are estimated in the isotropic as well as in the nematic phases.     

Crystal Growth from Silica Gels and Single Crystal Structure of Bariumchromate

Rhombic single crystals of bariumchromate were grown in silica gels up to 1.5 mm in size. The influence of the initial pH-value of the gel and the kind and concentration of reactants are studied. The crystal structure has been determined. The compound crystallizes in space group Pnma, with cell dimensions a = 9.113(4) Å, b = 5.528(3) Å, c = 7.336(4) Å and Z = 4. The structure was refined to R = 0.062 on the basis of 364 reflections. Every barium atome, centered in a distorted archimedian antiprism, is coordinated to 8 oxygen atoms each belonging to a chromate tetrahedron. Interatomic distances and bond angles were calculated.     

Crystal and molecular structure of decahydroquinoline hydrobromide,and its relation to piperidine hydrobromide

The structure of decahydroquinoline hydrobromide has been determined by the heavy-atom technique. This compound, C₉H₁₈NBr, crystallizes in the orthorhombic space groupPbcn (N ° 60), witha = 26.885(3),b = 9.952(1),c = 7.750(1) Å, andZ = 8. The structure was refined by block-diagonal least-squares methods to a finalR value of 0.086, including the hydrogen atoms located theoretically. Decahydroquinoline has a chair conformation. The molecules are held together by a network of hydrogen bonds of type N⁺–H...Br^– along thec axis, and by van der Waals forces in the other directions. A comparative study with the structure of piperidine hydrobromide is given.     

ThePoranthera corymbosa alkaloids. III. Molecular structure and absolute configuration of poranthericine hydrobromide

Crystals of the hydrobromide of poranthericine, C₁₅H₂₇NO, an alkaloid isolated from the plantPoranthera corymbosa Brogn. (family Euphorbiaceae) were found to belong to the orthorhombic space groupP2₁2₁2₁, with unit cell dimensionsa = 12·761,b = 15·144 andc = 8·030 Å, andZ = 4. The structure was solved by the heavy-atom method and refined with 1276 reflections to a residual of 0·091 The molecule was found to consist of three saturated six-membered rings fused on to a common central nitrogen atom, with methyl, ethyl and hydroxyl groups attached to the periphery. All rings had thechair conformation and were fusedtrans to one another. The absolute configuration was determined using the anomalous scattering power of the bromine atom.     

The Effective Temperature of Surfaces of Liquid Metals and Some Non-Metals

An estimation of decrease of atomic bond energy by raising temperature for surfaces of liquid metals and some non-metals had been made. The calculation values of the derivative du_sdu_b where u_s and u_b, are bond energy of atoms in surface and bulk of a liquid, are significantly above 1 and in limits from 2 to 10. It was supposed that this results from anomalously intensive thermal expansion of surface layers of liquids – the effect which is well known for crystal surfaces. This expansion was explained by the effective temperature of these surfaces which, thus, was found to be by several times above those for bulk of liquids.     

Synthesis and crystal structure of bis(4-methylpiperidine-dithiocarbamato-S,S′)-palladium(II)

The complex bis(4-methylpiperidine-dithiocarbamato-S,S′)-palladium(II) was synthesized by the reaction of 4-methyl-1-piperidine dithiocarbamic acid with palladium(II) chloride. Its structure was determined by X-ray crystal diffraction analysis. It crystallizes in the monoclinic P2₁/c space group with the crystal cell parameters a=8.6491(8) ?, b=18.7305(16) ?, c=11.9933(10) ?, β=107.074(1)°, V=1857.3(3) ?³ and Z=4. The palladium (II) ion is bonded to four sulfur atoms, belonging to two dithiocarbamate ligands, in a distorted square planar geometry. The X-ray data suggest a pronounced electronic delocalization in the two NCS₂ moieties.     

Synthesis,crystal and molecular structures of 1,8-diaza-11,14-dioxacyclohexadeca-2,7-dione and 1,10-diaza-4,7-dioxacyclohexadeca-2,9-dione

1,8-Diaza-11,14-dioxacyclohexadeca-2,7-dione (3) has been synthesized under high-pressure conditions, whereas 1,10-diaza-4,7-dioxacyclohexadeca-2,9-dione (6) has been obtained under thermal conditions. Both compounds have been investigated in the solid state and in solution by X-ray structural and NMR methods, respectively. The crystals of3 are orthorhombic, space groupPbca; the crystals of6 are triclinic, space groupP¯1. Both structures were solved by direct methods, and refined by a full-matrix, least-squares procedure giving for3 R=0.045 and for 6R=0.056 (R _w =0.065). From the NMR investigations in solution a twofold symmetry of both molecules (probably in intermediate conformations) is suggested; no such symmetry was found in crystalline state. The structure of6 exhibits a positional disorder of one O-heteroatoms with the population ratio 0.510.49. The arrangement of the macroring with respect to the carbonyl groups was found to betransoid in3 andcisoid in6.     

Synthesis and Molecular Structure Investigation by DFT and X-Ray Diffraction of ARNO

Abstract  

We report here the synthesis of (Z)-5-(4-nitrobenzyliden)-3-N(2-ethoxyphenyl)-2-thioxo-thiazolidin-4-one (ARNO) compound. The crystal structure has been determined by X-ray diffraction. The compound crystallizes in the triclinic system with space group P[`1] P\bar{1} and cell parameters: a = 9.1289(19), b = 9.3717(7), c = 12.136(3) ?, α = 102.133(11)°, β = 90.99(2)°, γ = 117.165(9)°, V = 895.4(3) ?³ and Z = 2. The structure has been refined to a final R = 0.05 for 2591 observed reflections. The refined structure was found to be significantly non planar. The molecule exhibits intermolecular hydrogen bond of type C–H⋯O and C–H⋯S. ab initio calculations were also were performed at Hartree–Fock and density functional theory levels. The full HF and DFT geometry optimization was carried out using LANL2DZ, 6-31G* and B3LYP/6-31+G** basis sets. The optimized geometry of the title compound was found to be consistent structure determined by X-ray diffraction. The minimum energy of geometrical structure is obtained by using level HF/LANL2DZ basis sets.     

A novel oxazine from the condensation of chloroanthraquinone and t-butyl L-prolinate

A new, fused-ring oxazine was synthesized in a one-pot condensation of L-proline t-butyl ester and 1-chloroanthraquinone. The compound crystallized in space group P2₁2₁2₁ with cell parameters a = 10.1820(10) Å, b = 15.213(2) Å, c = 18.649(2) Å, and Z = 4. The absolute structure of the compound was obtained by the Flack parameter.     

Dependence of Electrical Conductivity (σ) and Activation Energy of Lithium Ferrite on Sintering Temperature and Porosity

The electrical conductivity (σ) of lithium ferrite sintered at 950, 1000, 1050 and 1100 °C was investigated in the temperature range of 300 to 1000 K. Three distinct regions have been observed in log (σT) vs 10³/T curves for four samples of lithium ferrite sintered at different temperatures. The conduction in the first region is due to impurities. In the second and third region is due to ordered and disordered state of the material. The transition from the first region to the second region is due to lowering of symmetry. The transition from second to third region is due to magnetic transition, i.e. ferrimagnetic to paramagnetic state. The transition temperatures are nearly equal to the Curie temperatures of the materials. The porosity and activation energy were calculated. It was found that the electrical conductivity is progressively increasing with increase of sintering temperature while the porosity and activation energy decrease continuously. The Seebeck coefficient (Q), carrier concentration (n) and mobility (μ) of charge carriers have been discussed as a function of sintering temperature and temperature.     

Crystal and molecular structure of 10,20-epoxy-grayanotoxin-II

The photooxidation with HgO in benzene and the hydrolysis with 2%-KOH in methanol of the grayanotoxin (GTX) derivative (4) gave a 10,20-epoxy-grayanotoxin-II(5). The crystal structure of (5) has been determined by X-ray diffraction at room temperature. The crystal is monoclinic, space group P2₁, with a = 14.248(10) Å, b = 6.670(10) Å, c = 9.990(10) Å, = 105.507(8)°, V = 914.9(2) ų, Z = 2. The structure was solved by direct methods and refined by full-matrix least squares methods to a final R1 = 0.046 (wR2 = 0.0833) for 1161 independent reflections. The molecule has a pentacyclic structure consisting of two five-membered, one six-membered, one seven-membered, and one three-membered rings. The three-membered ring is connected with the seven-membered ring by spiro-type bond.     

ThePoranthera corymbosa alkaloids,II. Molecular structure and absolute configuration of porantheridine hydrobromide

Crystals of the hydrobromide of the alkaloid designated porantheridine, C₁₅H₂₇NO, isolated from the plantPoranthera corymbosa Brogn. (family Euphorbiacaea), belong to the space groupP2₁2₁2₁, with cell dimensionsa= 10·059,b = 16·704 andc = 9·629 Å. The crystal structure was solved by the heavy-atom method and refined with 624 reflexions to a residual of 0·078. The molecule consists of three six-membered rings fused on to a common central nitrogen atom; one ring contains an oxygen atom with ann-propyl group and a methyl group substituted on the vicinal carbon atoms. The rings have thechair conformation, two being fusedtrans to each other andcis to the third. The absolute configuration was determined using the anomalous scattering power of the bromine atom.     

Synthesis and Properties of Poly(N-vinylcarbazole) Covalently Functionalized Zinc Oxide Nanocomposites

Poly(N-vinylcarbazole) covalently grafted zinc oxide nanoparticles (ZnO-g-PNVC) were synthesized with a simple route using surface initiated reversible addition-fragmentation chain transfer (RAFT) polymerization. Initially, the surface of ZnO nanoparticles was modified by the condensation reaction of 3-chloropropyltrimethoxysilane, and it was subsequently reacted with potassium xanthogenate to produce ZnO nanoparticles having RAFT functionality (ZnO-RAFT). The controlled radical polymerization of N-vinylcarbazole in the presence of ZnO-RAFT afforded ZnO-g-PNVC composites. FT-IR, EDX, XRD, and SEM analyses demonstrated the grafting of PNVC onto ZnO nanoparticles. Thermal stability of ZnO-g-PNVC composites was revealed by TGA analysis. UV-Vis absorption and photoluminescence results suggested ZnO-g-PNVC composites as a potential material in optical application.     

Stereochemistry of diamination of (E)- and (Z)-2-butenes: Crystal and molecular structures of meso- and dl-2,3-diaminobutane ditosylates

Stereospecific anti-addition of diethyl N,N-dibromophosphoramidate (DBPA) to (E)- and (Z)-2-butenes was definitely corroborated by X-ray structural determinations ofthreo- anderythro-2-amino-3-bromobutane hydrochlorides prepared from the corresponding adducts without changing the configuration on either chiral centers. The stereochemistry of azidation ofthreo- anderythro-2-amino-3-bromobutane hydrochlorides leading todl- andmeso-2,3-diaminobutane ditosylates respectively (after reduction of an azide function) was deduced from an X-ray crystallographic analysis of these diamine salts. The X-ray crystallographic analysis was carried out for three compounds: two reaction products and substrate (Scheme 2).