膜萃取-气相色谱/微分离子迁移谱检测水中的1,4-二恶烷

利用膜萃取-气相色谱/微分离子迁移谱（ME-GC/DMS）对水中的1,4-二恶烷污染物进行了检测。考察了射频电压、采样流速、膜渗透时间、Trap预富集时间等参数对检测二恶烷的影响规律。结果显示：在优化条件下,二恶烷的定量线性范围为2.0~20.0 μg/L,检出限为0.67 μg/L。实验证明,二恶烷与5种氯代烃的混合物在ME-GC/DMS的二维分离谱图中得到特异性响应,增加了识别的准确性。该研究为发展现场实时监测地下水中污染物的方法提供了重要参考。     

Preferential solvation of indomethacin in 1,4-dioxane + water mixtures according to the inverse Kirkwood–Buff integrals method

The preferential solvation parameters (δx_1,3) of indomethacin (IMC) in 1,4-dioxane + water binary mixtures were derived from their thermodynamic properties by means of the inverse Kirkwood–Buff integrals method. δx_1,3 is negative in water-rich and 1,4-dioxane-rich mixtures but positive in cosolvent compositions from 0.17 to 0.69 in mole fraction of 1,4-dioxane at 298.15 K. It is conjecturable that in water-rich mixtures, the hydrophobic hydration around the aromatic and methyl groups of the drug plays a relevant role in the solvation. The higher solvation by 1,4-dioxane in mixtures of similar cosolvent compositions could be mainly due to polarity effects. Finally, the preference of this drug for water in 1,4-dioxane-rich mixtures could be explained in terms of the higher acidic behavior of water molecules interacting with the hydrogen-acceptor groups present in IMC.     

Complexation of a Macrocycle Containing Thiopyrimidine and Uracil Moieties with Dicarboxylic and Amino Acids in Various Organic and Aqueous Organic Solutions

The complexation of a macrocycle containing thiopyrimidine and uracil moieties (M) with amino acids and some dicarboxylic acids was studied by pH-metric, UV-VIS, ¹H NMR spectroscopy methods in chloroform, methanol, aqueous 1,4-dioxane, and biphasic water–chloroform media. The complexation of M with acids is too weak to solubilize them from the solid state into chloroform solutions containing M. The ¹H NMR spectra and pH-metric data of aqueous 1,4-dioxane (80 vol.%) reveal the pH-dependent 1:1 binding between M and the acids studied. The protonation of M is not a prerequisite for binding of fumaric, succinic, o-phtalic acids and the series of amino acids, whereas binding of maleic acid requires the protonation of both thiopyrimidine moieties of M. Therefore,M·(H⁺)₂ exhibits strong selectivity towards maleic acid in aqueous 1,4-dioxane and in biphasic water–chloroform media.     

“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.     

Development of dynamic headspace-liquid phase microextraction method performed in a home-made extraction vessel for extraction and preconcentration of 1,4-dioxane from shampoo

In the present study, a new, simple, rapid, and environmentally friendly headspace-liquid phase microextraction method followed by gas chromatography–flame ionization detection has been developed for the extraction/preconcentration and determination of 1,4-dioxane from shampoo. The developed procedure is performed in a home-made extraction vessel, connected to a glass vial containing sample and extraction solvent. In this method, an aliquot weight of shampoo is mixed with a binary mixture of n-hexane and dichloromethane (50:50, v/v) as the extractant and the target analyte is extracted during a liquid–liquid extraction procedure. Then a home-made extraction vessel containing a few microliters of a collection/extraction solvent is contacted to a glass vial containing the organic phase obtained from the previous step. By heating 1,4-dioxane is vaporized and enriched in a μL volume of the collection/extraction solvent. Then an aliquot volume of the collected phase is injected into the separation system. The effect of several factors which may influence performance of the method, including kind and volume of the extraction solvents used in both steps, extraction temperature, extraction time, and salt addition were evaluated. Under the optimum extraction conditions, limits of detection and quantification for the target analyte were obtained 0.52 and 1.73 μg kg^?1, respectively. Enrichment factor and extraction recovery were 333 and 89 %, respectively. The method precision was evaluated at a concentration of 25 μg kg^?1 and relative standard deviation was less than 6.9 % for intra-day (n = 6) and inter-day (n = 4) precisions. Finally, the proposed method has been successfully applied in analysis of 1,4-dioxane in different shampoo samples.     

Distribution of 1,4-dioxane by combined inhalation plus oral exposure routes in rats

1,4-Dioxane is used in large amounts by industry. Human exposure to 1,4-dioxane is via both air and water. Recently we reported that the toxicity of chloroform is enhanced when exposure is by multiple exposure routes rather than a single exposure route. In this study, rats were exposed simultaneously to 1,4-dioxane by two routes, inhalation and oral, and the distribution of 1,4-dioxane in the blood, lung, liver, brain, kidney and abdominal fat of rats were determined. To assess the contribution of each route, unmodified 1,4-dioxane (DX) was administered by inhalation and deuterated 1,4-dioxane (DX-d₈) was administered orally, and DX and DX-d₈ were analyzed by mass spectrometer (MS). Exposure by both inhalation and oral administration resulted in DX and DX-d₈ concentrations in the blood and tissues which were higher than when exposure was by either inhalation or oral administration alone. The distribution of 1,4-dioxane in the combined inhalation plus oral administration conformed with its physicochemical properties and the tissue partition coefficients. Our results support the well accepted tenet that when investigating the toxicity of a chemical, the route of exposure is an important consideration, and in addition, our results suggest that when exposure is by multiple routes, exposure by one route may, to some extent, have an affect on exposure by the second route.     

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.     

Solubility and preferential solvation of indomethacin in 1,4-dioxane + water solvent mixtures

The solubilities of indomethacin (IMC) in 1,4-dioxane + water cosolvent mixtures were determined at several temperatures, 293.15–313.15 K. The thermodynamic functions: Gibbs energy, enthalpy, and entropy of solution and of mixing were obtained from these data by using the van’t Hoff and Gibbs equations. The solubility was maximal in 0.95 mass fraction of 1,4-dioxane and very low in pure water at all the temperatures. A non-linear plot of ΔH_soln ° vs. ΔG_soln ° with negative slope from pure water up to 0.60 mass fraction of 1,4-dioxane and positive beyond this up to 0.95 mass fraction of 1,4-dioxane was obtained. Accordingly, the driving mechanism for IMC solubility in water-rich mixtures is the entropy, probably due to water-structure loss around the drug non-polar moieties by 1,4-dioxane, whereas, above 0.60 mass fraction of 1,4-dioxane the driving mechanism is the enthalpy, probably due to IMC solvation increase by the co-solvent molecules. The preferential solvation of IMC by the components of the solvent was estimated by means of the quasi-lattice quasi-chemical method, whereas the inverse Kirkwood-Buff integral method could not be applied because of divergence of the integrals in intermediate compositions.     

Cellulose decomposition behavior in hot-compressed aprotic solvents

Microcrystalline cellulose (avicel) is treated in hot-compressed aprotic solvents,sulfolane and 1,4-dioxane,using a batch-type reaction system with a molten tin bath in a range from 290 to 390℃. The corresponding densities of the solvent are 0.25-1.26 g/cm3 and 0.21-1.03 g/cm3 for sulfolane and 1,4-dioxane,respectively. As a result,in both solvents,more than 90% of cellulose is found to be de-composed to the solvent-soluble portion in which levoglucosan is the main component with the high-est yield of about 35% on original cellulose basis. The decomposition rate to levoglucosan is,however,faster in sulfolane than in 1,4-dioxane,while levoglucosan is more stable in 1,4-dioxane. In addition,its yield is found to be solvent-density dependent to be highest around 0.4-0.5 g/cm3 for both solvents. To elucidate these decomposition behaviors,the results obtained in this study with aprotic solvents are compared with protic solvents such as water and methanol in previous works.     

Mechanism of alternating copolymerization of 4-hydroxy-4′-vinylbiphenyl with α-chloromaleic anhydride

The copolymerization of 4-hydroxy-4′-vinylbiphenyl (HVB) with α-chloromaleic anhydride (CMAn) was investigated in THF, 1,4-dioxane, and acetonitrile. The formation of the 1:1 charge transfer complex between HVB and CMAn was confirmed spectroscopically, and the corresponding equilibrium constant (K_eq) was determined as follows: K_eq = 0.19, 0.11, and 0.058 mol/L in THF, 1,4-dioxane, and CH₃CN, respectively. The copolymer composition is affected by the solvent, i.e., the content of HVB in the copolymer obtained in THF or 1,4-dioxane is lower than 50 mol % whereas the copolymer obtained in CH₃CN has excess of HVB units. The maximum rate of copolymerization was observed at a 1:1 initial comonomer mole ratio, irrespective of the solvent polarity. Plots of R_p/[HVB] vs. [HVB] gave a straight line with a slope and an intercept for the copolymerization in THF whereas a straight line in CH₃CN has no slope. On the basis of these results and ¹³C-NMR spectra of the copolymers, the mechanism of the predominant formation of alternating copolymers is discussed.     

Iodine and Brønsted acid catalyzed C–C bond cleavage of 1,3-diketones for the acylation of amines

Abstract

A metal-free N-acylation method of anilines with 1,3-diketones has been developed, by using iodine and p-toluene sulfonic acid as the co-catalysts. The reaction can proceed in 1,4-dioxane at elevated temperature to produce the corresponding amides with 48–89% yields. Further, the gram-scale experiment was carried out under the standard conditions and the possible mechanism was proposed.     

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.     

顶空固相微萃取-气相色谱法测定生活饮用水中痕量1,4-二氧六环

建立了生活饮用水中痕量1,4-二氧六环的顶空固相微萃取(HS/SPME)-气相色谱测定方法。考察并优化了萃取头、萃取温度、萃取时间、pH值、样品量、色谱条件等参数。结果表明:提取效率较好的方法是3 mL水样中加入3 mL 600 g/L氢氧化钠溶液,用85 μm Carboxen-PDMS萃取头萃取,用键合碱改性的大口径、厚液膜PTA-5毛细管色谱柱测定。1,4-二氧六环在0.50~50.0 μg/L范围内线性关系良好,相关系数为0.9995;方法检出限(以S/N>3计)为0.14 μg/L;相对标准偏差为2.1%~4.5% (n=6);对实际样品中进行线性范围内的高、中、低3个加标水平的测定,回收率为95.5%~107%,相对标准偏差为1.1%~5.3% (n=6)。建立的方法简便、准确、重现性好、灵敏度高,适合生活饮用水中痕量1,4-二氧六环的常规监测。     

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.     

Polyamides of 2,5-bis(amino methyl) 1,4-dioxane and dicarboxylic acids

Novel polyamides of 2,5-bis(amino methyl) 1,4-dioxane (cis/trans-BAMD) with adipic/sebacic acids and of 2,5-bis(carboxy methyl)/2,5-bis(carboxy) 1,4-dioxane with 1,6-hexane diamine have been prepared. Because of the slightly higher conformational flexibility of the 1,4-dioxane ring in comparison with that of the cyclohexane ring, the BAMD polyamides have lower T_g and T_m than the corresponding 1,4-bis(amino methyl) cyclohexane (BAMC) polyamides. The symmetry of the trans-dioxane moiety permits high crystallinity in the trans-BAMD polymers. The crystallinity T_g and T_m of the trans polymers are decreased with the incorporation of the cis-dioxane moiety which lacks a plane of symmetry. Because of the hydrophilic nature of the dioxane ring, t-BAMD-6 has good moisture-regain properties, yet is melt processable (T_m = 292°C).     

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).     

Dehydration of 1,4-dioxane through blend membranes of poly(vinyl alcohol) and chitosan by pervaporation

Blend membranes prepared from poly(vinyl alcohol) (PVA) and chitosan (CS) were crosslinked with glutaraldehyde and used in the pervaporation dehydration of 1,4-dioxane. Membranes were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (X-RD) to assess, respectively, the intermolecular interactions, thermal stability and crystallinity. Equilibrium sorption studies were carried out in pure liquids and binary mixtures of different compositions of water + 1,4-dioxane mixtures to assess the polymer–liquid interactions. The crosslinked membrane showed a good potential in breaking the azeotrope of 82 wt.% aqueous 1,4-dioxane giving a selectivity of 117 with a reasonable water flux of 0.37 kg/m² h. The effect of operating parameters such as feed composition, membrane thickness and permeate pressure was evaluated.     

Zwitterionic spirocyclic λ5 Si-silicates with two cis-1,2-diphenylethene-1,2-diolato(2–) ligands: Synthesis and structural characterization

The zwitterionic ⁵ Si-silicates bis[cis-1,2-diphenylethene-1,2-diolato(2–)](morpholiniomethyl)silicate (2) and bis[cis-1,2-diphenylethene-1,2-diolato(2–)][(2,2,6,6-tetramethylpiperidinio)methyl]silicate (3) were synthesized by various methods, including remarkableSi–C cleavage reactions with benzoin. Treatment of trimethoxy(morpholinomethyl)silane (4), dimethoxy(morpholinomethyl)phenylsilane (5), or dimethoxy(methyl)(morpholinomethyl)silane (6) with two molar equivalents of benzoin in acetonitrile yielded 2. Compound 3 was synthesized by treatment of trimethoxy[(2,2,6,6-tetramethylpiperidino)methyl]silane (7) with two molar equivalents of benzoin in 1,4-dioxane/n-pentane and was isolated as the 1,4-dioxane solvate 3 ·3/2C₄H₈O₂. Compounds 2 and 3 ·3/2C₄H₈O₂ were structurally characterized by solution and solid-state NMR spectroscopy and by single-crystal X-ray diffraction. In addition, the dynamic behavior of 3 in solution was studied by VT ¹H NMR experiments.     

Inhibiting effect of 5-amino-5-methyluracil and its derivatives on the free-radical oxidation of 1,4-dioxane

The antiradical activity of 5-amino-6-methyluracil in the initiated radical-chain oxidation of 1,4-dioxane as a model system was studied quantitatively. The rate constant k ₇ of its reaction with the peroxyl radical of 1,4-dioxane was measured to be (5.6 ± 1.8) × 10⁵ L mol^?1 s^?1 at 333 K. The effect of the methyl substituents in the 1- and 3-positions of the uracil ring and in the amino group on the rate constant of inhibition was studied. The strengths of all N-H bonds in the 5-amino-6-methyluracil and its derivatives were calculated in the G3MP2B3 approximation and were compared with the measured rate constants of inhibition. By the example of the reaction of 5-amino-6-uracil with i-PrO ₂ ^?? , different attack pathways of the peroxyl radical at the N-H bonds of uracil were analyzed in the UB3LYP/6-311+G(d,p) approximation. The lowest activation barrier (5.8 kJ/mol) was observed for peroxyl radical attack on the (C⁵)N-H bonds. The site responsible for the inhibition activity of the compound is the amino group.     

Proton solvation in the sulfuric acid-water-1,4-dioxane system

The dependence of the optical density on the composition of the solution in the range of 0–60%, 1,4-dioxane in 10% aqueous solution of H₂SO₄ was obtained by FMIR IR spectroscopy. It was shown that in the solutions studied, the proton is in the form of the two simplest stable solvates: H₅O₂ ⁺ and H₂OHD⁺ ions, where D is the 1,4-dioxane molecule. The equilibrium concentrations of the proton solvates were estimated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 298–301, February, 1990.