1,4-二氧六环的光电离解离

采用同步辐射光源、飞行时间质谱和分子束方法研究了1．4-二氧六环的光电离解离过程．由光电离效率曲线得出离子产物的出现势，计算了产物的生成焓．若重分析了m／e=28,29.41等离子碎片的解离通道以及离子碎片的可能结构，提出1、4-二氧六环在光电离解离过程中发生了重排反应     

Thermodynamic investigation of AB and AB2 molecular species in binary liquid systems: Excess enthalpies of 1,4-dioxane with chloroform and bromoform

Excess enthalpies have been measured at 308.15 K for 1,4-dioxane (A) + chloroform (B) and 1,4-dioxane (A) + bromoform (B). The data have been examined on the basis of Barker's theory. Interaction energies between the components have been determined and the study suggests that these mixtures contain both AB and AB₂ molecular species.     

Crystal structure and dynamic properties of a bimetallic cyano complex Cd(C4H8O2)Cu(CN)3 with an interpenetrating 3D framework containing a 1,4-dioxane bridging ligand as a rotor

The title complex Cd(C(4)H(8)O(2))Cu(CN)(3) has a 3D twofold interpenetrating framework structure. The structural base of the framework is a planar hexagonal network complex of [Cu(CN)(3)Cd](infinity) ,which is formed with cyanides connecting the coordination sites of Cu(i) ions with a triangle planar form and the equatorial coordination sites of Cd(ii) ions with a trigonal bipyramid form. The networks are stacked and a 1,4-dioxane molecule coordinates to two Cd(ii) ions in alternate networks as a bridging ligand. The 1,4-dioxane ligand penetrates a hexagonal window of the network sandwiched between the bridged networks. This 1,4-dioxane bridge completes the 3D twofold interpenetrating framework structure. (2)H-NMR powder patterns of the deuterated complex Cd(C(4)D(8)O(2))Cu(CN)(3) revealed the dynamics of the 1,4-dioxane bridge as a rotor. Above 253 K, the 1,4-dioxane ligand undergoes rotational motion combined with a ring inversion between two chair conformations. The free energy of activation DeltaG(double dagger) for the ring inversion was calculated to be 41.4(7) kJ mol(-1) at 298 K.     

A molecular dynamics computer simulation study of the temperature dependence of hydration of 1,4-dioxane and 1,3-dioxane

This paper describes a study of the hydration of 1,3-dioxane and 1,4-dioxane at two different temperatures using different molecular dynamics (MD) computer simulation techniques. Three major conclusions have been drawn. Firstly, the simulations of 1,4-dioxane—water and 1,3-dioxane—water at constant pressure lead essentially to the same conclusions as earlir MD studies at constant volume. Secondly, the numerical values of dynamic properties depend critically on the density of the system. Simulations at constant pressure provide densities which are dependent on the periodicity requirement imposed on the system by the periodic boundary conditions. The smaller the periodic box, the stronger this effect is. Thirdly, in 1,4-dioxane—water an increase in temperature results in an enhanced mobility of water molecules in the solvation shell, whereas in the case of 1,3-dioxane—water these water molecules become more strongly bound by the solute. This effect is entirely due to a reduction of the mobility of water molecules in the 1,3-dioxane oxygen hydration subshells. The contrasting behavior is explained in terms of a situation where solvent—solvent interactions dominate solute—solvent interactions in 1,4-dioxane—water at both temperatures and in 1,3-dioxane—water at the lower temperature, while the opposite situation holds for 1,3-dioxane—water at the higher temperature.     

Molecular Interactions in 1,4-Dioxane,Tetrahydrofuran, and Ethyl Acetate Solutions of 1,1′-Bis(4-isopropyloxyacetylphenoxy)cyclohexane on Reological,Density, and Acoustic Behavior

Various thermo-acoustical parameters of 1,4-dioxane, tetrahydofuran and ethylacetae solutions of 1,1′-bis(4-isopropyloxyacetylphenoxy)cyclohexane were determined at different temperatures using density, viscosity and ultrasonic speed and correlated with concentration. Linear increase of ultrasonic speed, specific acoustical impedance, Rao’s molar sound function, Van der Waals constant and free volume with concentration C and decreased with temperature. Linear decrease of adiabatic compressibility, internal pressure, intermolecular free path length, classical absorption coefficient, and viscous relaxation time with concentration and increased with temperature indicated existence of strong molecular interactions in solutions and further supported by positive values of solvation number. Gibbs free energy of activation decreased with C in all three systems. It is decreased with T in 1,4-dioxane, while increased in tetrahydrofuran and ethyl acetate. Both enthalpy of activation and entropy of activation are increased gradually with C in 1,4-dioxane, while they are negative and remained practically independent of concentration in 1,4-dioxane and tetrahydofuran systems.     

Free-radical chain oxidation of 1,4-dioxane inhibited by 2-thio-6-aminouracil

The effect of 2-thio-6-aminouracil on the oxygen uptake kinetics has been studied in 1,4-dioxane free-radical chain oxidation as a model system. The presence of a thiocarbonyl group in the 2-position of the uracil ring makes 6-aminouracil highly reactive towards 1,4-dioxane peroxy radicals. The rate constant of the 1,4-dioxane peroxy radical interaction with 2-thio-6-aminouracil has been measured to be k₇ = (3.0 ± 0.5) × 10⁵ L mol^–1 s^–1 (333 K). The stoichiometric inhibition factor f = 1.1 ± 0.1 has been determined.     

Diffusion with molecular association in chloroform + triethylamine and chloroform + dioxane mixtures

The Taylor dispersion method is used to measure the binary mutual diffusion coefficients of chloroform + triethylamine and chloroform +1,4-dioxane at 25°C. The components of these mixtures associate, forming chloroform-triethylamine and chloroform-dioxane, (chloroform)₂-dioxane molecular complexes. A modified Hartley-Crank equation is developed to express the binary diffusion coefficient as a weighted average of the diffusion coefficients of the free molecules and the molecular complexes. Counterintuitively, the contribution made by each molecular complex to the overall diffusion coefficient vanishes when the concentration of the complex reaches its maximum value. The measured and fitted diffusion coefficients agree within 3% or better over the complete composition range.     

Hydrogen bonds in 1,4-dioxane/ammonia binary clusters

With synchrotron radiation, we have studied the photoionization and dissociation of 1,4-dioxane/ammonia clusters in a supersonic expansion. The observed major product ions are the 1,4-dioxane cation M(+) and protonated cluster ions M(NH(3))(n)H(+) (where M=1,4-dioxane), and the intensities of the unprotonated cluster ions M(NH(3))(n) (+) are much lower. Fully optimized geometries and energies of the neutral cluster M(NH(3))(2) and related cluster ions have been obtained using the ab initio molecular orbital method and density functional theory. The potential energy surface of the excited state of M(NH(3))(2) (+) was also calculated. With these results, the mechanisms of different photoionization-dissociation channels have been suggested. The most probable channel is electron ejection from the highest occupied molecular orbital, followed by the dissociation into M(+) and (NH(3))(2). For another main channel, after removing an electron from the second highest occupied molecular orbital, the intracluster proton transfer process takes place to form the stable unprotonated cluster ion M(NH(3))H(+)-NH(2), which usually leads to the dissociated protonated cluster ion M(NH(3))H(+) and a radical NH(2).     

Characterization of two linear chain compounds: Ferromagnet NiCl2(CH3OH)2(1,4-dioxane)0.5 (1) and paramagnet [NiCl2(H2O)2(1,4-dioxane)](1,4-dioxane) (2)

The solvent-mediated crystal-to-crystal transformation was observed from yellow crystal of NiCl₂(CH₃OH)₂(1,4-dioxane)_0.5 (1) to green crystal of [NiCl₂(H₂O)₂(1,4-dioxane)](1,4-dioxane) (2) under high humidity or adding of H₂O in CH₃OH/1,4-dioxane solution. The μ-Cl₂ bridge in 1 replaced by 1,4-dioxane bridge in 2. In 1, the chlorine-bridged linear chains of NiCl₂(CH₃OH)₂ and 1,4-dioxane molecules stack along the b- and c-axis alternatively with hydrogen bonds intrachain, interchain, between chain and solvent. These hydrogen bonds and dipolar interaction between ferromagnetic coupling chlorine-bridged chains result in long-range ferromagnetic ordering at 3.1 K and a strong frequency dependence of the ac-susceptibilities associated to domain structures with very large shape anisotropy was observed below 3.1 K. In 2, layers of 1,4-dioxane-bridged linear chains of NiCl₂(H₂O)₂(1,4-dioxane) are intercalated by layer of 1,4-dioxane molecules with hydrogen bonds between chain and solvent. Compound 2 is paramagnet to 2 K.     

Non-steady-state living polymerization: a new route to control cationic ring-opening polymerization (CROP) of oxetane via an activation chain end (ACE) mechanism at ambient temperature

Well-defined polyoxetane with low polydispersivity has been synthesized via a novel living polymerisation process using 3-phenoxypropyl 1,4-dioxanium hexafluoroantimonate (3-PPD) as a model of a living "monomeric polyoxetane" initiator, in 1,4-dioxane at 35 degrees C.     

“LIVING-LIKE” CATIONIC POLYMERIZATION OF ISOBUTYL VINYL ETHER INITIATED BY CARBOXYL GROUPS ON CARBON BLACK SURFACE/ETHYLALUMINUM DICHLORIDE SYSTEM IN THE PRESENCE OF 1,4-DIOXANE

The effect of 1,4-dioxane as an added base on the cationic polymerization of isobutyl vinyl ether (IBVE) initiated by carboxyl groups on carbon black surface/ethylaluminum dichloride (EtAlCl₂) system was investigated. Although the cationic polymerization of IBVE by carbon black/EtAlCl₂ system the absence of 1,4-dioxane instaneously proceeded and the monomer conversion achieved 100% within a minute. The molecular weight distribution (MWD) of polyIBVE obtained was very broad. On the contrary, the MWD of polyIBVE obtained was very narrow and narrower than that obtained from the carbon black/ZnCl₂ initiating system by the addition of 1,4-dioxane. The number-average molecular weight (Mn) of polyIBVE obtained was directly proportional to monomer conversion in the cationic polymerization. However, the Mn of polyIBVE obtained from the polymerization by the initiating system in the the presence of 1,4-dioxane was smaller than that of the calculated value, assuming that polyl(IBVE) chain forms per unit carboxyl group on carbon black surface. It was concluded that carbon black/EtAlCl₂ initiating systems in the presence of 1,4-dioxane has an ability to initiate “living-like” cationic polymerization of IBVE based on the above results. PolyIBVE was grafted onto a carbon black surface after quenching the above “living-like” cationic polymerization systems with methanol.     

Preparation,molecular and crystal structures of 3-(1-amino-2,2,2-trifluoroethylidene)-1,1,4,5,6,7-hexafluoroindan-2-one, 2-amino-1,1,4,5,6,7-hexafluoro-3-trifluoroacetylindene,and their complexes with dioxane and pyridine

3-(1-Amino-2,2,2-trifluoroethylidene)-1,1,4,5,6,7-hexafluoroindan-2-one (2) is synthesized by the interaction between 3-(1-amino-2,2,2-trifluoroethylidene)-2-imino-1,1,4,5,6,7-hexafluoroindan (1) and isopropylnitrite, and 2-amino-1,1,4,5,6,7-hexafluoro-3-trifluoroacetylindene (3) is prepared by hydrolysis. Single crystals are grown, and the molecular and crystal structure of enaminoketones obtained, the complex of compound 2 with 1,4-dioxane, and the complex of compound 3 with pyridine is studied. DFT calculations have been performed to find the complex formation energies of compounds 2 and 3 with dioxane and pyridine in the gas phase.     

Density and Speed of Sound for Binary Mixtures of a Cyclic Ether with a Butanol Isomer

Densities and speeds of sound of the binary mixtures 1,3-dioxolane + 1-butanol, 1,3-dioxolane + 2-butanol, 1,4-dioxane + 1-butanol, and 1,4-dioxane + 2-butanol have been measured at 25 and 40°C. The excess molar volumes and excess isentropic compressibility coefficients were calculated from experimental data and fitted to a Redlich–Kister polynomial function. Results were analyzed in terms of molecular interactions and compared with literature data.     

X-ray structural investigation of gossypol and its derivatives XXIII autoclathrates based on a mixed gossypol — 1,4-Dioxane matrix

Gossypol forms various complexes with the isomeric dioxanes. The clathrate with 1,4-dioxane is the only complex of gossypol in which the intrinsic symmetry of the gossypol molecule — the symmetry of a twofold axis — is retained. In this complex, two out of the three 1,4-dioxane molecules belonging to each gossypol molecule participate in the construction of a mixed H-bound gossypol -dioxane matrix, while the third molecule plays the part of guest, the guest molecules having no H-bonds with the host matrix and undergoing desolvation at 108–110°C.     

Synthesis and properties of diphenoxo-bridged CoII, NiII, CuII, and ZnII complexes of a new tripodal ligand: generation and properties of MII-coordinated phenoxyl radical species

Four dinuclear complexes of composition [MII2(L)2].xS [M=Co, x=0.5, S=1,4-dioxane (1.0.5 1,4-dioxane); Ni, x=0 (2) [single crystals have x=2, S=diethyl ether (2.2 diethyl ether)]; Cu, x=0 (3); Zn, x=0.5, S=1,4-dioxane (4.0.5 1,4-dioxane)] have been synthesized using a new tripodal ligand [2,4-di tert-butyl-6-{[(2-pyridyl)ethyl](2-hydroxybenzyl)-aminomethyl}-phenol (H2L)], in its deprotonated form, providing a N 2O 2 donor set. Crystallographic analyses reveal that the complexes have a similar diphenoxo-bridged structure. Each metal ion is terminally coordinated by 2,4-di tert-butyl-phenolate oxygen, a tertiary amine, and a pyridyl nitrogen. From each ligand, unsubstituted phenolate oxygen provides bridging coordination. Thus, each metal center assumes M (II)N 2O 3 coordination. Whereas the geometry around the metal ion in 1.0.5 1,4-dioxane, 2.2 diethyl ether and, 4.0.5 1,4-dioxane is distorted trigonal-bipyramidal, in 3 each copper(II) center is in a square-pyramidal environment. Temperature-dependent magnetic behavior has been investigated to reveal intramolecular antiferromagnetic exchange coupling for these compounds (-J=6.1, 28.6, and 359 cm(-1) for 1.0.5 1,4-dioxane, 2, and 3, respectively). Spectroscopic properties of the complexes have also been investigated. When examined by cyclic voltammetry (CV), all four complexes undergo in CH2Cl2 two reversible ligand-based (2,4-di tert-butylphenolate unit) one-electron oxidations [E1/2(1)=0.50-0.58 and E1/2(2)=0.63-0.75 V vs SCE (saturated calomel electrode)]. The chemically/coulometrically generated two-electron oxidized form of 3 rearranges to a monomeric species with instantaneous abstraction of the hydrogen atom, and for 4.0.5 1,4-dioxane the dimeric unit remains intact, exhibiting an EPR spectrum characteristic of the presence of ZnII-coordinated phenoxyl radical (UV-vis and EPR spectroscopy). To suggest the site of oxidation (metal or ligand-centered), in each case DFT calculations have been performed at the B3LYP level of theory.     

Thermodynamic analysis of surface formation of {1,4-dioxane + 1-alkanol} mixtures

Surface tensions (sigma) for {1,4-dioxane + methanol, ethanol, or 1-propanol} at the temperature 298.15 K and normal atmospheric pressure have been determined as a function of mole fractions. The experimental results have been analyzed using the ideal and Langmuir models and in the light of the well-documented bulk properties of these systems, which reflect hydrogen bonding between the alcohol and 1,4-dioxane molecules. For {1,4-dioxane + ethanol} surface tensions were also measured at other temperatures between 288.15 and 308.15 K, and these data were used to calculate the surface entropy and enthalpy per unit area.     

一种具有二维状组装体结构的氢键结合超分子水凝胶的制备

近年来,基于低分子量有机凝胶因子(low molecular mass organic gelators)[1]形成的超分子水凝胶得到了广泛关注.     

Solvent-driven association and dissociation of the hydrogen-bonded protonated decavanadates

Hydrogen-bond-assisted molecular aggregation of decavanadate anions, [H(n)V(10)O(28)]((6-n)-), in non-aqueous solutions was probed by systematic small-angle X-ray scattering and (1)H and (51)V NMR spectroscopic measurements in mixtures of acetone and 1,4-dioxane. Under acetone-rich conditions, the decavanadate anion prefers a self-associated hydrogen-bonded dimer of {[H(3)V(10)O(28)](2)}(6-), which dissociates into monomeric species as the proportion of 1,4-dioxane increases. The association/dissociation behaviors of the decavanadate anions were proven to be reversible and driven by the protophobic/protophilic nature of the solvent.     

Excess enthalpies of water+1,4-dioxane at 278.15, 298.15, 318.15 and 338.15 K

The excess molar enthalpies of (1–x)water+x1,4-dioxane have been measured at four different temperatures. All the mixtures showed negative enthalpies in the range of low mole fraction but positive ones in the range of high mole fraction of 1,4-dioxane. Excess enthalpies were increased with increasing temperature except those of at 278.15 K. Partial molar enthalpies have maximum around x=0.13 and minimum around x=0.75. Three different behaviors for the concentration dependence of partial molar enthalpies were observed for all temperature. Theoretical calculations of molecular interactions of three characteristic concentrations were carried out using the molecular orbital method.