Theoretical studies of the structure of nitrimines. I. Structure of 2-nitroguanidine and its alkyl derivatives

The molecular structure of 2-nitroguanidine and its 1-methyl, 1-ethyl, and 1,1,3,3-tetramethyl derivatives was studied by quantum-chemical methods. The results were compared with X-ray data. Using a basis larger than 6-31G and polarization functions and including electron correlation in calculations did not improve agreement with experiment. The major reason for this is the considerable effect of the crystal field on the geometrical parameters of the molecules.     

A new waterNa(+) coordination motif in an unexpected diatrizoic acid disodium salt crystal form

The disodium salt of diatrizoic acid crystallises as a tetragonal channel hydrate structure. One of the incorporated water molecules is coordinated to three individual sodium cations in a unique geometry.     

Challenges of crystal structure prediction of diastereomeric salt pairs

A methodology for the computational prediction of the crystal structures and resolution efficiency for diastereomeric salt pairs is developed by considering the polymorphic system of the diastereomeric salt pair (R)-1-phenylethylammonium (R/S)-2-phenylpropanoate. To alleviate the mathematical complexity of the search for minima in the lattice energy due to the presence of two flexible entities in the asymmetric unit, the range of rigid-body lattice energy global optimizations was guided by a statistical analysis of the Cambridge Structural Database for common ion-pair geometries and ion conformations. A distributed multipole model for the dominant electrostatic interactions and high-level ab initio calculations for the intramolecular energy penalty for conformational distortions are used to quantify the relative stabilities of the p- and n-salt forms. While the ab initio prediction of the known structure of the p-salt as the most stable structure was insensitive to minor changes in the rigid-ion conformations considered, the relative stabilities of the known polymorphs and hypothetical structures of the n-salt were very sensitive. Although this paper provides a significant advance over traditional search algorithms and empirical force fields in determining the structures and relative stabilities of diastereomeric salt pairs, the sensitivity of the computed lattice energies to the fine details of the ion conformations overtaxes current computational models and renders the design of diastereomeric resolution processes by computational chemistry a challenging problem.     

α-羟基二茂铁类衍生物的合成及其晶体结构

通过甲酰基二茂铁与苯乙酮，硝基甲烷及丙酮的缩合反应，我们制得了其缩合产物-α-羟基-β-羰基化合物。并对甲酰基二茂铁与苯乙酮的缩合产物进行了X射线单晶结构分析。结果表明：该晶体属于单斜晶系，空间群为P 2~1/n，a=0.6022(1)，b=2.735(1)，c=0.9416(1)nm，β=99.02(1)°，V=1.532(1)(nm)^3，Mr=334.20，Z=4，Dx=1.45g/cm^3，μ=9.68cm^-^1，F(000)=696。     

Synthesis and crystal structure of two derivatives of benzodiazepines

Two benzodiazepine derivatives, C₂₃H₂₂N₂O (I), 2-methyl-8-methoxy-2,4-diphenyl-2,3-dihydro-1H-1,5-benzodiazepine, and C₂₂H₁₇N₃O₂Br₂ (II), 2-methyl-7-nitro-2,4-bis(4′-bromophenyl)-2,3-dihydro-1H-1,5-benzodiazepine, were studied by single crystal X-ray diffraction method. Compound (I) crystallizes in the monoclinic system, space group P2₁/c, a = 13.1703(17) Å, b = 11.1990(14) Å, c = 12.9093(16) Å, β = 107.831(2)°, V = 1812.6(3) ų, Z = 4. Compound (II) crystallizes in the monoclinic system, space group P2₁/n, a = 11.7345(12) Å, b = 12.7477(13) Å, c = 13.5965(14) Å, β = 95.221(2)°, V = 2025.4(4) ų, Z = 4. The molecules of (I) and (II) have T-shape form with the diazepine ring at the junction point. The seven membered central benzodiazepine ring in both structures adopt a twist-boat conformation. The crystal packing is stabilized by C-H…π (in I) and C-H…O (in II) interactions.     

Benzamidinium acetylsalicylate: crystal structure of the first salt with acetylsalicylate anion

The first crystal structure of a non-coordinating acetylsalicylate anion containing salt was determined by X-ray crystallography. Benzamidinium acetylsalicylate crystallizes in the triclinic space group $ P\bar{1} The first crystal structure of a non-coordinating acetylsalicylate anion containing salt was determined by X-ray crystallography. Benzamidinium acetylsalicylate crystallizes in the triclinic space group (a = 9.8885(5), b = 10.2769(5), c = 15.2656(7) ?, α = 87.219(4), β = 78.261(4) and γ = 72.589(4) Z = 4, V = 1449.17(12) ?³, R1 = 0.0346 and wR2 = 0.0697). The structure comprises pairs of hydrogen bonded benzamidinium cations and acetylsalicylate anions connected into infinite chains through further N–H···O hydrogen bonds.     

Novel rearrangement and crystal structure of tetraarylated dihydrosemibullvalene derivatives

The structure of a dihydrosemibullvalene,

, previously deduced from nmr and mass spectrometry and from chemical transformation of an analogue - is confirmed by X-ray analysis. The thermal rearrangement of other analogous arylated dihydrosemibullvalenes is disclosed.     

Quantum-chemical study of the spiropiperidine alkaloids ofNitraria I. Intramolecular hydrogen bonds and chemical properties of nitramine and isonitramine

Preferential conformations have been found for nitramine and isonitramine on the basis of quantum-chemical calculations of various conformational states. The results obtained have been correlated with spectral characteristics and chemical properties.Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 897–902, November–December, 1996. Original article submitted May 6, 1996.     

具有生物活性的1,4-二氢吡啶衍生物的水热法合成及结构表征

1,4-二氢吡啶衍生物具有很好的生理活性。在医学上用作心血管疾病的防治保健药物,不仅能治疗肠胃疾病、雷诺氏病、脂肪肝、中毒性肝炎,也有抗衰老、防早熟等作用,还可以用作治疗肺动脉高压和癫痫病的辅助药物[1-2]。近年又发现1,4-二氢吡啶衍生物不但是一类高效的钙拮抗剂,亦是一种绿色饲料添加剂。它的合成通常采用文献报道的Hantzsch法合成[3],即将干燥氨气通入乙酰乙酸乙酯与醛的混合溶液中。该反应时间长、操作复杂,且氨气易对环境造成污染。正因为此,越来越多的化学家和药物学家将有机合成的研究重点放在对环境无污染的绿色合成上。如…     

Natural and synthetic polymers as reagents. I. Diazonium salt derivatives of polycarboxylic resins (insoluble diazonium salt chromogens)

A method is described for the preparation of insoluble polymeric diazonium-salt chromogens which have a precise composition and well-defined specific reactivity and which are capable of undergoing coupling reactions to produce highly colored azo derivatives. The technique involves reaction of the acid chloride of an acrylic or methacrylic acid polymer crosslinked with divinylbenzene with an aromatic diamine, followed by diazotization of the free amino groups of the resultant aminoarylamido resin to give an insoluble diazonium salt. The aminoarylamido derivatives, the corresponding diazonium salts, and colors of the azo derivatives obtained in coupling reactions are tabulated.     

Structure of a potassium-ion-exchanged nepheline hydrate I crystal

A nepheline hydrate I crystal, ion-exchanged using KCl(aq) at 80°C, was found to be orthorhombic, space group Pnm2₁, a = 8.113(3), b = 15.223(2), c = 5.1817(7)Å and showed no superlattice X-ray reflections. Structure analysis by means of Fourier and least-squares methods led to the composition K_1.1Na_1.9Al₃Si₃O₁₂ · H₂O (Z = 2, D_c = 2.40 g cm^?3) and the agreement factors: R = 0.032 and R_w = 0.040. Species assigned to the observed extra framework sites were K(1), K(2), and W(1) in the 8-ring tunnels along c plus Na(1) and Na(2) in the smaller 6-ring voids forming connections in the b direction. The atoms Na(1) and Na(2) coordinated framework oxygens exclusively and were but little affected by the ion-exchange process; K(1) was found near the center of an 8-ring and had five O atoms and two water molecules as closest neighbors, while the weakly occupied K(2) site was near a 6-ring and was found to have a coordination consisting of at least five oxygens and one water. The 10% vacancy of Na(2) is compensated for by an equal amount of K(2), which does not enter the Na(2) site for sterical reasons.     

The crystal structure of thenoyltrifluoroacetonatocarbonyltriphenylphosphinerhodium (I)

The crystal structure of thenoyltrifluoroacetonatocarbonyltriphenylphosphinerhodium (I), [Rh(TTA) (CO) PPh₃], has been determined by single crystal X-ray diffraction. 2665 independent observed reflections were used for the structure determination. The crystals are monoclinic, space group P2₁/n with a = 13.26Å; b = 10.86Å; c = 18.92Å; β = 69.8° with four molecules in the unit cell. The final R value for all the reflections was 0.052. The compound was prepared by substitution of one of the carbonyl groups in Rh(TTA) (CO)₂ by triphenylphosphine. The structure determination shows that the carbonyl group trans to the oxygen nearest to the thenoyl ring was substituted by the phosphine group. The distance between the rhodium atom and the latter oxygen atom is 0.033Å longer than the other RhO distance.     

X-ray structural investigation of glyoxime derivatives II. Molecular and crystal structure of diaminotetraoxime

A. N. Nesmeyanov Institute for Heteroorganic Compounds, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 1, pp. 179–180, January–February, 1989.     

Molecular and crystal structure of derivatives of higher internal perfluoroalkenes

Institute of Heteroorganic Compounds, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 2, pp. 199–203, March–April, 1989.     

Thermal behavior of iminodiacetic acid and its disodium salt

The thermal properties of iminodiacetic acid (IDA) and its disodium salt were investigated by DTA, TG and static heating. The gaseous evolved products were analysed by chromatography in order to follow the thermal process. The heating of the samples was stopped at characteristic decomposition steps and the residual substances were investigated by IR spectroscopy. The obtained data suggest the processes of decomposition for these compounds.