Adsorption and photocatalytic degradation of 1,4-dioxane on TiO2

1,4-Dioxane in hexane as a solvent was adsorbed on TiO₂ due to an electrostatic interaction. The porous TiO₂ pellets (SG) prepared by sol–gel method were superior adsorbent to ST-B21 and Degussa P-25. Effects of firing temperature of the pellets and the initial concentrations of 1,4-dioxane on the adsorption percents were examined. Photocatalytic degradation of aqueous 1,4-dioxane gave 1,2-ethanediol diformate and formic acid as intermediates. Analysis of total organic carbon indicated that 1,4-dioxane was mineralized effectively in the following order: P-25 > ST-B21 > SG. The photocatalytic degradation of 1,4-dioxane adsorbed on the TiO₂ pellets in air showed that ST-B21 had a higher activity than SG. These facts indicate that SG pellet acts as a good adsorbent because of its high specific surface area but the internal region of the pores is not illuminated and acts only as a support.     

Thermochemical behavior of crown ethers in the mixtures of water with organic solvents. Part VIII. Hydrophobic hydration and preferential solvation of 1,4-dioxane in {(1 − x)amide + xH2O} at T = 298.15 K

The enthalpies of solution of 1,4-dioxane in {(1 − x)F + xH₂O}, {(1 − x)NMF + xH₂O}, and {(1 − x)DMF + xH₂O} have been measured within the whole mole fraction range at T = 298.15 K. Based on the obtained data, the effect of substituting methyl groups at the nitrogen atom in formamide on the preferential solvation of 1,4-dioxane has been analyzed. A simple model has been proposed to describe the influence of structural and energetic properties of the mixed solvent on the energetic effect of hydrophobic hydration and preferential solvation of 1,4-dioxane by the components of the examined mixture.     

Excess enthalpies and excess heat capacities of binary mixtures of (cyclohexanone,or 2-butanone,or 1,4-dioxane + 1,2-dimethoxyethane) and (1,4-dioxane + 1,2-dimethoxyethane) atT = 298.15 K

Excess enthalpies and excess heat capacities of { x 2-butanone  +  (1  − x)1,4-dioxane}, and { x cyclohexanone, or 2-butanone, or 1,4-dioxane  +  (1  − x)1,2-dimethoxyethane} were measured atT =  298.15 K. Excess enthalpies were negative for { x 2-butanone  +  (1  − x)1,2-dimethoxyethane}, and negative with a small positive part in the region ofx >  0.8 for { x cyclohexanone  +  (1  − x)1,2-dimethoxyethane}, whereas excess enthalpies of { x 2-butanone  +  (1  − x)1,4-dioxane} were positive as for { x cyclohexanone  +  (1  − x)1,4-dioxane} previously reported. Excess enthalpies of {x 1,4-dioxane  +  (1  − x)1,2-dimethoxyethane} were positive. The results were compared with the systems reported earlier. Excess heat capacities are positive for { x 2-butanone  +  (1  − x)1,2-dimethoxyethane} and { x cyclohexanone  +  (1  − x)1,2-dimethoxyethane}, and negative for { x 2-butanone  +  (1  − x)1,4-dioxane} and { x 1,4-dioxane  +  (1  − x)1,2-dimethoxyethane}. The last mixture shows a W-shaped curve of excess heat capacity.     

Molecular Stark-effect spectroscopy of Prodan and Laurdan in different solvents and electric dipole moments in their equilibrated ground and Franck–Condon excited state

The results from electrooptical absorption measurements (EOAM) on the ground and excited Franck–Condon state dipole moments of Prodan and Laurdan in 1,4-dioxane and cyclohexane are presented. The ground and excited Franck–Condon state electric dipole moments as well as the respective transition moment of both probes are parallel. The electric dipole moments of Prodan and Laurdan in the ground state in cyclohexane and 1,4-dioxane have values within the range (15.7–16.5) × 10⁻³⁰ C m. On optical excitation the dipole moments increase by (42.1–49.5) × 10⁻³⁰ C m. The obtained results are compared with the values of the dipole moments of Prodan and Laurdan determined by other methods.     

Synthesis of 2,3-dihydropyrroles by photo rearrangement of Hantzsch 1,4-dihydropyridines with high diastereoselectivity

The Hantzsch 1,4-dihydropyridines were found to be transforming to the 2,3-dihydropyrroles by photo rearrangement with air under irradiation of LED light (410 nm) with high diastereoselectivity (dr > 20:1). This reaction includes tandem photo oxidation/rearrangement. The 2,3-dihydropyrroles were obtained in moderate yields with successfully one-pot process starting from aldehydes, ammonium acetate and ethyl acetoacetate.     

Synthesis of a reduction-sensitive Bletilla striata polysaccharide amphiphilic copolymer

A reduction-sensitive stearic acid modified-Bletilla striata polysaccharide amphiphilic copolymer is synthesized. The copolymer enabled to spontaneously form micelles which display faster docetaxel release rates under reduction condition and enhanced anticancer activity in vitro after incorporating docetaxel into micelles.     

Organocatalytic chemoselective monoacylation of 1,n-linear disulfonamides

Predominant monoacylation of 1,n-linear disulfonamides took place in the presence of pyrrolidinopyridine-type organocatalysts when the chain length of the linear disulfonamides was n = 3, 4, or 5 (monoacylate/diacylate = up to 44). The chemoselectivity of the competitive acylation between N,N′-ditosyl-1,5-pentanediamine (n = 5) and N,N′-ditosyl-1,3-propanediamine (n = 3) was found to be 36, favoring the former substrate. Different chain length by only one carbon atom was discriminated in the competitive acylation between N,N′-ditosyl-1,5-pentanediamine (n = 5) and of N,N′-ditosyl-1,4-butanediamine (n = 4) with the relative acylation rate of 16 in the presence of the organocatalyst.     

Description of intra-diffusion in liquid mixtures

Employing a previously derived model to describe intra-diffusion coefficients in liquid mixtures based on molecular simulations of spherical Lennard–Jones particles [T. Merzliak, A. Pfennig, Mol. Simul. 30 (7) (2004) 459–468], an improved set of coefficients was obtained from optimized molecular dynamics simulations. In these simulations, the thermodynamic states were planned with the help of optimal experimental design, which allows to reduce the number of simulations necessary for significant determination of the coefficients by roughly a decade. The model was then applied to the real liquid mixtures toluene + cyclohexane, toluene + 1,4-dioxane, n-hexane + toluene, 1,4-dioxane + cyclohexane and cyclohexane + n-hexane, which have molecular properties that correspond to the model assumptions. Experimental intra-diffusion coefficients for the mixtures toluene + cyclohexane, toluene + 1,4-dioxane, n-hexane + toluene and 1,4-dioxane + cyclohexane were determined with nuclear magnetic resonance (NMR) techniques in this work. Even without additional parameters for the mixture the proposed model can describe the diffusion coefficients with an average accuracy of 5%. Allowing a deviation from Lorentz–Berthelot mixing rules leads generally only to slight improvement.     

Nickel(0)/N-heterocyclic carbene complexes catalysed arylation of aromatic diamines

Nickel complexes of N-heterocyclic carbenes were examined for effecting C–N coupling reactions between aromatic diamines and aryl chlorides of varying electron density. The Ni(0) · 2IPr (IPr = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) complex associated to t-BuONa allowed N,N′-diarylation at 100 °C in 1,4-dioxane with excellent yields. Selective monoarylation of diamines could be performed in THF at 65 °C.     

Enantioselective synthesis of new oxazolidinylthiazolidines as enzyme inhibitors

The synthesis of new oxazolidinylthiazolidines bicycles, oxygen analogues of bisthiazolidines, also known as metallo-β-lactamase inhibitors is described. The reaction of β-aminoalcohols and 2,5-dihydroxy-1,4-dithiane led to oxazolidinylthiazolidines and/or dithioazabicycles as the main products. The distribution pattern depends mainly on the aminoalcohol substituents. In a one-pot reaction, four new bonds are formed in good yields and with high atom efficiency. When the oxazolidinylthiazolidines are formed, two stereogenic centres are generated with high enantiospecificity. The reaction mechanism is discussed based on crystallographic data and interconversion studies. Two oxazolidinylthiazolidines were evaluated as inhibitors of the potent lactamase NDM-1 and compound 4f displayed competitive inhibition with K_i = 1.6 ± 0.6 μM.     

Surface study of mixtures containing cyclic ethers and isomeric chlorobutanes

Experimental surface tensions and the corresponding surface tensions deviations for the mixtures containing 1,3-dioxolane or 1,4-dioxane and 1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane or 2-chloro-2-methylpropane, measured with a drop volume tensiometer, are reported at the temperatures of 298.15 K and 313.15 K. The excess surface concentrations of isomeric chlorobutanes are also evaluated using a monolayer model.     

Excess enthalpies and excess volumes of (2-methoxyethanol + 1,4-dioxane) and (1,2-dimethoxyethane + benzene) at temperatures between 283.15 K and 313.15 K

The measurement of excess enthalpies, H^E, at T=298.15 K and densities at temperatures between 283.15 K and 313.15 K are reported for the (2-methoxyethanol + 1,4-dioxane) and (1,2-dimethoxyethane + benzene) systems. The values of H^E and the excess volumes, V^E, are positive, and the temperature dependence of V^E is quite small for (2-methoxyethanol + 1,4-dioxane). The (1,2-dimethoxyethane + benzene) system shows a negative H^E and sigmoid curves in V^E, which change sign from positive to negative with an increase in 1,2-dimethoxyethane. The temperature dependence of V^E for this system is negative.     

Thermochemical behaviour of crown ethers in the mixtures of water with organic solvents. Part IX. Effect of base–acid properties of {(1 − x)AN + xH2O} on the solution enthalpy of cyclic ethers in this mixed solvent at T = 298.15 K

The enthalpies of solution of cyclic ethers: 1,4-dioxane, 12-crown-4 and 18-crown-6 in {(1 ? x)AN + xH₂O} have been measured over the whole mole fraction range at T = 298.15 K. Based on the results obtained, the effects of base–acid properties of mixed solvent and the number of –CH₂CH₂– groups in cyclic ethers molecules on the solution enthalpy of cyclic ethers in {(1 ? x)AN + xH₂O} have been analyzed.     

A rapid and sensitive UPLC–MS/MS method for quantitative determination of arformoterol in rat plasma,lung and trachea tissues

A rapid and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC–MS/MS) method was developed and fully validated for determination of arformoterol in rat plasma, lung and trachea tissues.     

Excess molar enthalpies of 1,3-dioxolane,or 1,4-dioxane with isomeric butanols

Using a flow-mixing calorimeter, excess molar enthalpies of 1,3-dioxolane, or 1,4-dioxane, with isomeric butanols were determined at the temperatures of 298.15 K and 313.15 K. All the studied systems show positive excess molar enthalpies. The results are compared with calculated values from the UNIFAC model.     

Photocatalytic hydrogen production from acidic aqueous solution in BODIPY-cobaloxime-ascorbic acid homogeneous system

For the first time, iodinated BODIPY dyes with phenylamine or 8-hydroxylquinoline moiety at the meso-position on the BODIPY core were tested for the light-driven production of H₂ from the acidic aqueous solutions.     

Dielectric properties of binary mixtures of three butanediols with 1,4-dioxane and 2-ethyl-1-hexanol at T = 298.2 K

Experimental results of dielectric investigations for solutions of the three butanediols {2,3-butanediol (2,3BD), 1,3-butanediol (1,3BD), and 1,4-butanediol (1,4BD)}, in 1,4-dioxane (1,4DX) are reported for various mole fractions at T = 298.2 K. Values of relative permittivity were measured at 100 kHz. The molecular dipole moments were determined using Guggenheim method. The variations of effective dipole moment and correlation factor, g, with mole fraction in these materials were investigated using Kirkwood–Frohlich equation. Dielectric measurements were also carried out on binary polar mixtures of the butanediols with 2-ethyl-1-hexanol (2EH) for various concentrations at T = 298.2 K. The Kirkwood correlation factor, the Bruggeman factor, and the excess permittivity were determined.     

Thermophysical study of 1,4-dioxane with cycloalkane mixtures

Densities, refractive indices, and surface tension for the binary mixtures 1,4-dioxane with cyclopentane or cylohexane have been determined at ambient pressure and at T = (283.15, 298.15, and 313.15) K. Excess volumes and refractive index and surface tension deviations have been calculated from the experimental data. Several relations between the thermophysical properties studied here have been tested using our experimental results.     

The effect of NDGA-modified etchant on the enzymatic degradation resistance and mechanical properties of collagen matrix

Bio-modified etchant can significantly improve the biostability of demineralized dentin collagen matrix, which validates the concept of etch-andcrosslink in dentin bonding.