Dielectric properties of ethyleneglycol-1,4-dioxane mixtures using TDR method

Complex permittivity has been determined for mixtures of ethyleneglycol-1,4-dioxane (EG-DX) with various concentrations in the frequency range from 100 MHz to 30 GHz at 25 degrees C by time domain reflectometry (TDR). A primary process with an asymmetric shape and a Debye-type small-amplitude high-frequency process are observed for each mixture. The deviation of the relaxation time for the primary process from that of the ideal mixture shows a maximum value at a mole fraction of 1,4-dioxane, xDX approximately =0.8. The static permittivity for the mixtures can be explained using the Luzar model by assuming the formation of two types of hydrogen-bonded dimers, one between EG-EG (pair 1) and the other between EG-DX (pair 2). The number of these pairs is also estimated as a function of concentration. These results of the relaxation time and static permittivity are interpreted on the basis of a model of two kinds of cooperative domains coexisting in the mixtures.     

Volumetric and refractive properties of binary mixtures containing 1,4-dioxane and chloroalkanes

Refractive index deviations, excess volumes, and molar refractions of binary mixtures containing 1,4-dioxane and 1-chloropropane or isomeric chlorobutanes have been calculated from experimental data of refractive indices and densities at temperatures of 298.15 K and 313.15 K. Results obtained have been discussed in terms of intermolecular interactions and a comprehensive discussion has been provided. Excess volumes have been also correlated using Peng–Robinson–Stryjek–Vera cubic equation of state and the relation between parameter b (covolume) from the equation of state and molar refraction has been verified. Refractive indices were compared with those predicted using the equation of state and several mixing rules.     

Calorimetric study of solvation of alkanes with mixtures of acetone or 1,4-dioxane with 1-octanol at 25°C

Heats of solution of cyclohexane and squalane in mixtures of 1-octanol with acetone or 1,4-dioxane within the entire range of compositions were measured calorimetrically. The enthalpies of solution of cyclohexane, squalane, and hexadecane in the mixtures of acetone or 1,4-dioxane with 1-octanol show linear correlation. Enthalpies of solvation of propane, decane, and eicosane in these mixtures were calculated.     

Binary mixtures of cyclohexanone, 2-butanone, 1,4-dioxane and 1,2-dimethoxyethane

Densities and sound velocities of binary mixtures of cyclohexanone, 2-butanone, 1,4-dioxane and 1,2-dimethoxyethane were measured at 298.15 K and also the densities at 303.15 K. Excess volumes were determined from densities. Isentropic compressibilities were determined from densities and sound velocities, and excess thermal expansion factors were determined from excess volumes of two temperatures. Excess isothermal compressibilities and excess isochoric heat capacities were then estimated using excess isobaric heat capacities previously reported. Excess volumes and excess isentropic and isothermal compressibilities were negative except for cyclohexanone+1,4-dioxane system. This revised version was published online in August 2006 with corrections to the Cover Date.     

Gas-phase oxidation of 1,4-dioxane

An experimental investigation in a conventional static apparatus of the oxidation of equimolecular mixtures 1,4-dioxane-O₂ has shown that 1,4-dioxane reacts with oxygen more readily than most hydrocarbons. Cool flames and ignitions were observed above 200°C in a pressure range up to 300 torr. The products of the slow reaction and cool flame were analyzed by gas chromatography and GC-MS; the slow reaction gives only CO, CO₂, H₂CO, H₂, C₂H₄, and H₂O. A radical chain mechanism is suggested and discussed by using an evaluation of the rate constants of the possible elementary steps by the methods of thermochemical kinetics.     

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.     

Unsaturated benzo-1,4-dioxane derivatives

Reaction of 6-chloromethylbenzo-1,4-dioxane with triethyl phosphite gives a phosphonate, the condensation of which with aldehyde gives unsaturated compounds containing a benzo-1,4-dioxane ring.     

Nitration of phenol in 1,4-dioxane

The nitration of phenol with excess nitric acid in aqueous dioxane, in contrast to the nitration in aqueous ethanol, yields exclusively 2,4-dintrophenol, whereas at equimolar ratio of phenol and nitric acid the major reaction products are mononitrophenols (99%), among which the p-isomer prevails.     

Homolytic amination of benzo-1,4-dioxane

When 5,6-benzo-1,4-dioxane was reacted with N,N-dialkylchloramines in the presence of FeSO₄ at 10–20C in a solution of acetic and sulfuric acids, 6-(N,N-dialkylamino)benzo-1,4-dioxanes and 6-chloro- and 6,7-dichloro-benzo-1,4-dioxanes were obtained. Under the conditions used in the study mainly chlorination products were synthesized. Reaction of 5,6-benzo-1,4-dipxane with the system (NH₃OH)₂SO₄-TiCl₃ resulted in the formation of 6-aminobenzo-1,4-dioxane.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 316–318, March, 1989.     

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.     

Synthesis of acetylenic derivatives of 1,4-dioxane

Cyclic ketals — 2,5-dimethyl-2,5-bis(4-penten-2-ynyloxy)-1,4-dioxane and 2,5-dimethyl-2,5-bis(3-phenyl-2-propynyloxy)-1,4-dioxane — were isolated in the reaction of propargyl alcohol with vinyl- and phenylethynylcarbinols in the presence of HgO-BF₃.O(C₂H₅)₂ catalytic system.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1029–1030, August, 1986.     

Ternary excess molar enthalpies for the mixtures of methanol and ethanol with tetrahydropyran or 1,4-dioxane at 298.15 K

Ternary excess molar enthalpies, H_m^E, at 298.15 K and atmospheric pressure measured by using a flow microcalorimeter are reported for the (methanol+ethanol+tetrahydropyran) and (methanol+ethanol+1,4-dioxane) mixtures. The pseudobinary excess molar enthalpies for all the systems are found to be positive over the entire range of compositions. The experimental results are correlated with a polynomial equation to estimate the coefficients and standard errors. The results have been compared with those calculated from a UNIQUAC associated solution model in terms of the self-association of alcohols as well as solvation between unlike alcohols and alcohols with tetrahydropyran or 1,4-dioxane. The association constants, solvation constants and optimally fitted binary parameters obtained solely from the pertinent binary correlation predict the ternary excess molar enthalpies with an excellent accuracy.     

Heat capacities of binary cycloalkane mixtures at 298.15 K

Volumetric heat capacities of the six binary mixtures formed from cyclopentane, cyclohexane, cycloheptane and cyclooctane were determined at 298.15 K in a Picker flow microcalorimeter. Excess heat capacities obtained from the results are compred with the temperature variation of excess enthalpies from the literature.     

On the radiation-induced polyaddition of bisperfluoroisopropenyl terephthalate with 1,4-dioxane

Radical polyaddition of bis(α-trifluoromethyl-β,β-difluorovinyl)terephthalate [CF₂C(CF₃)OCOC₆H₄COOC(CF₃)CF₂] (BFP) with 1,4-dioxane (DOX) afforded higher molecular weight polymers under γ-rays radiation from a source when compared to those yielded by benzoyl peroxide initiation. More detailed study on the radiation-induced polyaddition of BFP with DOX and optimization of the reaction conditions were carried out. It was necessary to irradiate with doses of 2000, 1500, and 750 kGy, to obtain quantitative conversion of BFP at the feed molar ratios DOX/BFP of 8.0, 16, and 32, respectively. Step-growth polymerization mechanism was suggested by the measurements of molecular weights of the polymers obtained with several irradiation doses. It was concluded that the molecular weight of the polymer could be controlled by the feed molar ratio of DOX/BFP and irradiation doses. The steep increase of molecular weight was observed at the feed molar ratio of DOX/BFP of 8.0 with the irradiation doses above 2000 kGy and the polymer with the weight-average molecular weight of 2.36×10⁴ was obtained with the dose of 3000 kGy. The reaction between polymers might take place after the quantitative conversion of BFP. Radiation-induced radical polyaddition mechanism of BFP with DOX was proposed.     

Thermal polymerization of N-tert-butylacrylamide in 1,4-dioxane

The kinetics of the thermal polymerization of N-tert-butylacrylamide were investigated in 1,4-dioxane as solvent, in the 65–80°C temperature range. It was found that the overall rate of polymerization which was determined by a gravimetric method is proportional to the 1.9 power of monomer concentration at 70°C. The rate of initiation was determined by ESR spectroscopy using DPPH as an inhibitor, and it was found that the order of initiation rate is 1.8 with respect to monomer concentration at 70°C. The overall activation energy for the thermal polymerization of N-tert-butylacrylamide was found to be 64 ± 9 kJ mol^?1 in the 65–80°C temperature range. The activation energy for the rate of initiation was also determined and it was found to be 90 ± 23 kJ mol^-1.     

Kinetics of chloromethylation of benzo-1,4-dioxane

The chloromethylation of benzo-1,4-dioxane in acetic acid in presence of SnCl₄, SbCl₃, ZnCl₂, and SbCl₅ catalysts was investigated. The activation energy of the process was found to be 19.6 kcal/mole. The reaction is zero order in chloride ion and first order in the Hammett acidity function. In excess HCl the reaction is described by a second-order equation. The relative activities of the methyl chlorides in the chloromethylation of benzo-1,4-dioxane were determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 459–462, April, 1981.     

Homolytic alkylation of benzimidazole by 1,4-dioxane

The homolytic alkylation of benzimidazoles by 1,4-dioxane has been studied. Introduction of an ethyl group at position 1 and a sulfonic group at position 2 of the heterocycle lowers the yield of products of substitution of hydrogen or the sulfonic group at position 2 by a dioxanyl radical.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 791–792, June, 1988.     

A shock tube and theoretical study on the pyrolysis of 1,4-dioxane

The dissociation of 1, 2 and 4% 1,4-dioxane dilute in krypton was studied in a shock tube using laser schlieren densitometry, LS, for 1550-2100 K with 56 ± 4 and 123 ± 3 Torr. Products were identified by time-of-flight mass spectrometry, TOF-MS. 1,4-dioxane was found to initially dissociate via C-O bond fission followed by nearly equal contributions from pathways involving 2,6 H-atom transfers to either the O or C atom at the scission site. The 'linear' species thus formed (ethylene glycol vinyl ether and 2-ethoxyacetaldehyde) then dissociate by central fission at rates too fast to resolve. The radicals produced in this fission break down further to generate H, CH(3) and OH, driving a chain decomposition and subsequent exothermic recombination. High-level ab initio calculations were used to develop a potential energy surface for the dissociation. These results were incorporated into an 83 reaction mechanism used to simulate the LS profiles with excellent agreement. Simulations of the TOF-MS experiments were also performed with good agreement for consumption of 1,4-dioxane. Rate coefficients for the overall initial dissociation yielded k(123Torr) = (1.58 ± 0.50) × 10(59) × T(-13.63) × exp(-43970/T) s(-1) and k(58Torr) = (3.16 ± 1.10) × 10(79) × T(-19.13) × exp(-51326/T) s(-1) for 1600 < T < 2100 K.