Room-temperature monoclinic and low-temperature triclinic phase-transition structures of meso-octa­methyl­calix­[4]­pyrrole–di­methyl sulfoxide (1/1)

Crystals of the title complex, C₂₈H₃₆N₄·C₂H₆OS, undergo a phase transition between room temperature and 198 K, as determined by X-ray diffraction techniques. A monoclinic form is observed at room temperature, while a triclinic modification is found at 198 K, with Z′ changing from 1 to 2. Differential scanning calorimetry (DSC) of the calix­pyrrole–di­methyl sulfoxide complex revealed a series of phase changes between 273 and 243 K. The transition from the room-temperature monoclinic form to the low-temperature triclinic form is reversible, as determined by changes in the cell dimensions from remeasuring selected reflections at room temperature and at temperatures below 223 K. The uncomplexed calix­[4]­pyrrole mol­ecule shows no phase changes occurring between room temperature and 233 K, the low-temperature limit of the DSC.     

Di­chloro­bis(4-methyl­pentan-2-onato-C4,O)­tin(IV) and bis(4-methyl­pentan-2-onato-C4,O)(2-thio­xo-1,3-di­thiole-4,5-di­thiol­ato-S,S′)­tin(IV) at 150 K

The structures of the ketotins determined here, [SnCl₂(C₆H₁₁O)₂] and [Sn(C₃S₅)(C₆H₁₁O)₂], respectively, along with that previously reported for [MeC(O)CH₂CMe₂]₂SnI₂, are compared with the structures of the analogous estertins [MeOC(O)CH₂CH₂]₂SnX₂. Pairwise comparison of the mean ketotin [estertin] Sn—X and Sn—O distances as Sn—X 2.4422 (4) [2.4054 (7) Å], 2.4970 (4) [2.471 (2) Å] and 2.8463 (4) [2.7788 (8) Å] and Sn—O 2.4926 (12) [2.528 (1) Å], 2.6110 (11) [2.629 (7) Å] and 2.435 (3) [2.525 (4) Å] (for X = Cl, S and I, respectively) clearly demonstrates the superior donor ability of the ketotin O atom in chelate formation.     

Synthesis of tris(β,β,γ-oximinoalkyl)amines from aliphatic nitro compounds and methyl vinyl ketone

A general strategy for the assembly of previously unknown tris(β,β,γ-oximinoalkyl)amines from aliphatic nitro compounds and methyl vinyl ketone is described. The strategy involves N,N-bis(siloxy)enamines as key intermediates. The latter are accessible by double silylation of alkylnitro compounds. Nickel(II) and copper(II) complexes of tris(β,β,γ-oximinoalkyl)amines are prepared and structurally characterized.     

Study of the fluorescence of 9,9′-bianthryl in polyvinylalcohol and in polyvinylchloride at 300 K and 80 K

By UV-vis spectroscopy and use of the polarization of the emission, we show that the 9,9′-bianthryl (9,9′BA) symmetrical molecule exhibits an induced fluorescence in polyvinylalcohol (PVA) by hydrogen bonding of the type OH⋯π which depends on considered temperature. This anomalous behaviour does not occur when this molecule is included in a polyvinylchloride, aprotic polymer.     

Viscometric and volumetric properties of benzene + methyl acetate,or + methyl propanoate,or + methyl butanoate binary systems at 283.15, 298.15 and 313.15 K

Viscosities and densities of three binary liquid mixtures, benzene?+?methyl acetate, benzene?+?methyl propanoate and benzene?+?methyl butanoate, have been measured at 283.15, 298.15 and 313.15?K, and atmospheric pressure. From experimental data, viscosity deviation, excess energy of activation for viscous flow, and excess molar volume were calculated and satisfactorily correlated with Redlich and Kister equation. Empirical and semiempirical equations and the predicted group-contribution method, universal automatic computer, were applied.     

Synthesis and Characterization of Alkyl and Aryl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amines: X‐Ray Structures of Ethyl and Cyclohexyl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amine

Abstract

We have synthesized and characterized a series of alkyl and aryl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amines through a high‐yield, three‐step procedure starting from 4‐methylquinolin‐2‐ol. Nitration using concentrated nitric/sulfuric acids, followed by chlorination in phosphorus oxychloride, yielded 2‐chloro‐4‐methyl‐6‐nitro‐quinoline. All of the intermediates and aminated products have been characterized by multinuclear (¹H and ¹³C) NMR spectroscopy, elemental analysis, and, in the case of the two title compounds (ethyl and cyclohexyl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amine), a single crystal X‐ray structure was obtained to verify the nature of the new materials.     

Synthesis and Crystal Structure of 1,4-Dimethyl-2,5-di{[2’-(3-pyridylmethylamino-formyl)phenoxyl]methyl}benzene Perchlorate

The title compound, 1,4-dimethyl-2,5-di{[2’-(3-pyridylmethylaminoformyl)phenoxyl]- methyl}benzene perchlorate (C36H36Cl2N4O12, Mr = 787.59), has been synthesized and structurally determined by single-crystal X-ray diffraction. The crystal crystallizes in the orthorhombic system, space group Pbca with a = 14.366(4), b = 15.159(4), c = 16.443(5), V = 3580.9(17)3, Z = 4, Dc = 1.461 g/cm3, μ = 0.253 mm-1, F(000) = 1640, R = 0.0618 and wR = 0.1525 for 1615 observed reflections (I > 2σ(I)). In the structure of the title compound, a two-dimensional supramolecular layer is formed via intermolecular hydrogen bonding interactions.     

The i.r. and Raman spectra of sodium hexafluorophosphate monohydrate,NaPF6·H2O

The i.r. and Raman spectra of NaPF₆·H₂O and partially deuterated NaPF₆·H₂O have been obtained. All of the fundamental modes of the PF⁻₆-ion have been located and the rule of mutual exclusion applies for these modes. In the Raman spectra, the number of components observed for each fundamental PF⁻₆-mode is consistent with the number of site group components predicted. The hydrogen bonds in NaPF₆·H₂O are very weak and the hydrogen bond energy is of the order of 1.7 kcal/mole. The frequencies of the nine fundamental modes of the H₂O, D₂O and HDO molecules have been converted to harmonic values. It is shown that if the HOH valence angle is varied, and the effective harmonic force field of the water molecules calculated for each assumed value, an estimated value of this angle in NaPF₆·H₂O can be obtained. The librational modes of the water molecules have been located and are assigned to rocking and wagging modes.     

The vibrational spectra of germane and silane derivatives—X. Trifluoro(methyl)-silane and -germane revised

A reinvestigation of the vibrational spectra of CH₃SiF₃ has lead to a more complete assignment than is currently available. An extension of the methods used has prompted a reassignment of the skeletal modes of CH₃GeF₃ and is believed to have lead to a settling of the assignment of CH₃GeCl₃, for which several versions exist.     

Synthesis and Crystal Structure of 1,4-Dimethyl-2,5-di{[2′-（3-pyridylmethylamino- formyl）phenoxyl]methyl}benzene Perchlorate

The title compound, 1,4-dimethyl-2,5-di { [2′-（3-pyridylmethylaminoformyl）phenoxyl]- methyl}benzene perchlorate （C36H36Cl2N4O12, Mr = 787.59）, has been synthesized and structurally determined by single-crystal X-ray diffraction. The crystal crystallizes in the orthorhombic system, space group Pbca with a = 14.366（4）, b = 15.159（4）, c = 16.443（5）A, V = 3580.9（17）/A3 Z = 4, De = 1.461 g/cm^3, /t = 0.253 mm^-1, F（000） = 1640, R = 0.0618 and wR = 0.1525 for 1615 observed reflections （I 〉 2σ（I））. In the structure of the title compound, a two-dimensional supramolecular layer is formed via intermolecular hydrogen bonding interactions.     

Theoretical investigation of the atmospheric chemistry of methyl difluoroacetate: reaction with Cl atoms and fate of alkoxy radical at 298 K

A theoretical study on the mechanism of the reactions of methyl difluoroacetate (MDFA) CF₂HC(O)OCH₃ with Cl atoms is presented. Two conformers relatively close in energy have been identified for MDFA. Geometry optimization and frequency calculations have been performed at the MPWB1K/6-31+G(d,p) level of theory, and energetic information is further refined by calculating the energy of the species using G2(MP2) theory. Transition states (TSs) are searched on the potential energy surface involved during the reaction channels, and each of the TSs is characterized by the presence of only one imaginary frequency. The existence of TSs on the corresponding potential energy surface is ascertained by performing intrinsic reaction coordinate calculation. Our calculations reveal that hydrogen abstraction from the –CH₃ group is thermodynamically and kinetically more facile than that from the –CF₂H group. Theoretically calculated rate constants at 298 K using the canonical transition state theory are found to be in good agreement with the experimentally measured ones. The atmospheric lifetime of CF₂HC(O)OCH₃ was estimated to be 16 years. The atmospheric fate and the main degradation process of alkoxy radical CF₂HC(O)OCH₂O are also discussed for the first time. Our calculation indicates that the fluorine atoms substitution has deactivating effect for the α-ester rearrangement.     

Synthesis and Crystal Structure of 3,3-Dimethyl-7,11-di（thiophene- 2-yl）-2,4-dioxyspiro[5. 5]undecane- 1,5,9-trione

The title compound （C19H18O5S2） has been synthesized by the reaction of thio- phene-2-carboxaldehyde, isopropylidene malonate and 4-chloroaniline using [bmim]Br as solvent, and characterized by IR, ^1H NMR and X-ray single-crystal diffraction. The crystal belongs to monoclinic, space group P21/n with a = 9.4872（15）, b = 9.5148（13）, c = 20.634（3）A, β= 92.209（2）°, V= 1861.2（4）A^3, Mr= 390.45, Z = 4, Dc = 1.393 g/cm^3,μ（MoKα） = 0.313 mm^-1, F（000） = 816, the final R = 0.0685 and wR = 0.1685. X-ray analysis reveals that two six-membered rings adopt chair and planar conformations, respectively.     

The regioselectivity of dibutylstannylene-mediated oxidation of methyl 3',4'-O-isopropylidene-α- and β-lactoside. A new synthesis of n -acetylllactosamine

The dibutylstannylene-mediated oxidation of methyl 3',4'-O-isopropylidene-a-lactoside (1) under different conditions using bromine as oxidizing agent has been investigated. The regioselectivity of this reaction strongly depends on the solvent and the nature of the added base. The 2-keto derivative, isolated as the corresponding methyloximino (10) or benzyloximino (13) derivatives, is the only oxidation product when acetonitrile is used as solvent and tributyltin methoxide as base. The oxidation of methyl 3',4'- O -isopropylldene-β-lactoside (5) under the same conditions results in regioselective oxidation at C-3. The simple regiosetective oxidation of the α-anomer (1) leads, after hydrogenation of the oximes (10 and 13) derived from the resulting 2-keto derivative, to lactosamine derivatives in a simple and convenient manner.     

The bulk properties of the water-dimethylsulfoxide system at 278–323.15 K and atmospheric pressure

The densities of water-dimethylsulfoxide (DMSO) mixtures were measured over the temperature range 278–323.15 K and over the whole range of compositions at atmospheric pressure. The partial molar volumes of water and dimethylsulfoxide, mixture volumetric thermal expansion coefficients, and partial molar volumetric thermal expansion coefficients of the components were calculated. The composition dependences of the density of the mixture passed a maximum at x ～ 0.6 at all temperatures (x is the mole fraction of dimethylsulfoxide). The composition dependences of the partial molar volumes of water and DMSO also passed extrema.     

The enthalpies and kinetic of dissolution of diterpenoid derivative—paclitaxel in aqueous NaCl solutions at 309.5 K

The enthalpies of dissolution of paclitaxel in normal saline were measured using a RD496-2000 Calvet Microcalorimeter at 309.65 K under atmospheric pressure. The differential enthalpy (Δ_dif H _m ) and molar enthalpy (Δ_sol H _m) of dissolution of paclitaxel innormal saline were determined. The corresponding kinetic equation described the dissolution process was elucidated to be dα/dt = 10^?3.57(1 ? a)^1.15. Moreover, the half-life, Δ_sol H _m , Δ_sol G _m and Δ_sol S _m of the dissolution process were also obtained. This work will provide a potential reference for the clinical application of paclitaxel.