Thermodynamic and optical studies of some ethylene glycol ethers in aqueous solutions at T = 298.15 K

Experimental results of density (ρ), speed of sound (u), and refractive index (n_D) have been obtained for aqueous solutions of ethylene glycol monomethyl ether (EGMME), ethylene glycol monoethyl ether (EGMEE), diethylene glycol monomethyl ether (DEGMME), and diethylene glycol monoethyl ether (DEGMEE) over the entire concentration range at T = 298.15 K. From these measurements, the derived parameters, apparent molar volume of solute (?_V), excess molar volume (V^E), isentropic compressibility of solution (β_S), apparent molar isentropic compressibility of solute (?_KS), deviation in isentropic compressibility (Δβ_S), molar refraction [R]_1,2 and deviation in refractive index of solution (Δn_D) have been calculated. The Redlich–Kister equation has been fitted to the calculated values of V^E, Δβ_S and Δn_D for the solution. The results obtained are interpreted in terms of hydrogen bonding and various interactions among solute and solvent molecules.     

Drastic solid-state fluorescence enhancement behaviour of imidazo[4,5-a]naphthalene-type fluorescent hosts upon inclusion of polyethers and tert-butyl alcohol

As one of the most promising materials for the construction of desirable solid-state fluorescent system, new solid-state fluorescent host-guest system, which consists of the imidazo[4,5-a]naphthalene-type fluorescent hosts 2 and sterically hindered guest molecules were designed and prepared. The crystals of 2 exhibit sensitive colour change and drastic fluorescence enhancement behaviour upon polyethers (diethylene glycol dimethyl ether (DGDM), diethylene glycol diethyl ether (DGDE) and diethylene glycol dibutyl ether (DGDB)) or tert-butyl alcohol. A comparison of the X-ray crystal structures of the guest-free and polyether- and tert-butyl alcohol-inclusion compounds indicates that the enclathrated polyether or tert-butyl alcohol molecule decrease the π-stacking between hosts and enlarge the distance between the host-host aromatic planes. On the bases of the spectral data and the crystal structures, the effects of the enclathrated sterically hindered guest on the drastic solid-state fluorescence enhancement behaviour of the host-guest crystals are discussed.     

Simultaneous determination of six hydrophilic ethers at trace levels using coconut charcoal adsorbent and gas chromatography/mass spectrometry

The main objective of the following study was to determine the efficiency of a method that uses coconut charcoal as a solid-phase extraction (SPE) adsorbent in order to simultaneously detect six hydrophilic ether species in water in the low microgram-per-liter range. The applied method was validated for quantification of ethyl tert-butyl ether, 1,4-dioxane, ethylene glycol dimethyl ether (monoglyme), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme) and tetraethylene glycol dimethyl ether (tetraglyme). SPE followed by gas chromatography/mass spectrometry of the extracts using the selected ion monitoring mode allowed for establishing low detection limits in the range of 0.007–0.018 μg/L in ultrapure water and 0.004–0.020 μg/L in environmental samples. Examination of the method accuracy and precision resulted in a recovery greater than 86.8 % for each compound with a relative standard deviation of less than 6.6 %. A stability study established a 5-day holding time for the unpreserved water samples and extracts. Finally, 27 samples obtained from surface water bodies in Germany were analyzed for the six hydrophilic ethers. Each analyte was detected in at least eight samples at concentrations reaching 2.0 μg/L. The results of this study emphasize the advantage of the method to simultaneously determine six hydrophilic ether compounds. The outcome of the surface water analyses augments a concern about their frequent and significant presence in surface water bodies in Germany.     

Thermophysical properties of methanol+some polyethylene glycol dimethyl ether by UNIFAC and DISQUAC group-contribution models for absorption heat pumps

Several group-contribution models including three different versions of UNIFAC, GC-UNIMOD and DISQUAC are tested for their capabilities of predicting vapour–liquid equilibria, excess enthalpies and viscosities of methanol+some polyethylene glycol dimethyl ethers over a wide range of temperature. Also, the literature experimental thermophysical property database of these serial systems are collected, and new experimental excess enthalpies of methanol+pentaethylene glycol dimethyl ether at 303.15 K and densities and kinematic viscosities of methanol with monoethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or pentaethylene glycol ether at 303.15 K are reported as a supplement to this experimental database. The predictions for vapour–liquid equilibria and excess enthalpies from modified UNIFAC of Gmehling et al. are the best, yielding the average relative deviation around 3% for vapour pressure and 30% for excess enthalpy. GC-UNIMOD viscosity group-contribution model gives the average relative deviation around 20% for viscosity predictions of the studied systems     

Thermodynamic Study of Oxyethylated Glycols and Their Mixtures with Tertiary Carboxamides

The contributions into the total energy of intermolecular interactions in oxyethylated ethylene glycol derivatives were estimated in terms of a model approach that uses inner pressure as a measure of nonspecific interactions in a liquid. Increased number of ether groups in ethylene glycols increases the nonspecific contribution and decreases specific contributions. Unlike diethylene glycol, triethylene glycol and tetraethylene glycol contain H-bond networks in the range 298.15–308.15 K. The enthalpies of mixing of tertiary amides with tetraethylene glycol were measured and compared with those for ethylene glycol, diethylene glycol, and triethylene glycol. The effect of the structural and thermodynamic properties of the components on the integral and differential thermochemical characteristics of mixtures of glycols with N,N-disubstituted amides was discussed.     

XAS/EXAFS studies of Ge nanoparticles produced by reaction between Mg2Ge and GeCl4

We present results of an XAS and EXAFS study of the synthesis of Ge nanoparticles formed by a metathesis reaction between Mg₂Ge and GeCl₄ in diglyme (diethylene glycol dimethyl ether). The progress of the formation reaction and the products formed at various stages in the processing was characterised by TEM and optical spectroscopy as well as in situ XAS/EXAFS studies using specially designed reaction cells.     

Nanoporous crosslinked macrocyclic polyethers based on diethylene glycol divinyl ether and their superbase complexes with KOH

Nanoporous (11–12 nm) crosslinked macrocyclic polyethers with vinyloxy and hydroxyl groups have been synthesized by the free-radical polymerization of diethylene glycol divinyl ether (AIBN, 80°C, i-octane), followed by acidic hydrolysis. It has been shown that the polymers react with KOH to form insoluble superbase complexes and alcoholates capable of catalyzing vinylation of ethylene glycol by acetylene.     

Excess Volumetric and Spectroscopic Properties of Mixtures of Some <Emphasis Type="Italic">n</Emphasis>-Alkoxyethanols and of Some Polyethers with 2-Pyrrolidinone and <Emphasis Type="Italic">N</Emphasis>-Methyl-2-Pyrrolidinone at 298.15 K

Excess molar volumes V_m^E for binary liquid mixtures of n-alkoxyethanols or polyethers + 2-pyrrolidinone or N-methyl-2-pyrrolidinone have been measured with a continuous dilution dilatometer at 298.15 K and atmospheric pressure as a function of composition. The alkoxyethanols are diethylene glycol monomethylether, 2-(2-methoxyethoxy) ethanol, CH₃(OC₂H₄)₂OH; diethylene glycol monoethylether, 2-(2-ethoxyethoxy) ethanol, C₂H₅(OC₂H₄)₂OH; and diethylene glycol monobutylether, 2-(2-butoxyethoxy) ethanol, C₄H₉(OC₂H₄)₂OH; whereas the polyethers are diethylene glycol dimethylether, bis(2-methoxyethyl)ether, CH₃(OC₂H₄)₂OCH₃; diethylene glycol diethylether, bis(2-ethoxyethyl)ether, C₂H₅(OC₂H₄)₂OC₂H₅; and diethylene glycol dibutylether, bis(2-butoxyethyl)ether, C₄H₉(OC₂H₄)₂OC₄H₉. In all mixtures the excess molar volumes are negative and symmetric across the entire composition range. The excess volumes are fitted to the Redlich–Kister polynomial equation to obtain the binary coefficients and the standard errors. The experimental results have also been discussed on the basis of IR measurements.     

Speeds of sound,densities, isentropic compressibilities of the system (methanol + polyethylene glycol dimethyl ether 250) at temperatures from 293.15 to 333.15 K

In this work, our objective is to contribute to the knowledge of the mixtures (alcohol + polyalkyl ether glycol) used in absorption refrigeration systems and heat pumps. The determination of different thermophysical properties is essential to understand the interactions among different molecules in liquid mixtures. Therefore, experimental data of speed of sound and density together with calculated values of isentropic compressibility for the refrigerant-absorbent system (methanol + polyethylene glycol dimethyl ether 250) (or Pegdme 250) have been gathered here over the whole range of composition at temperatures from T=293.15 to 333.15 K and atmospheric pressure. The two previous experimental properties were measured with a digital vibrating tube analyser Anton Paar DSA-48. Also, the excess molar volumes and the increments of the speed of sound and the isentropic compressibility have been determined for each composition and they were fitted to a variable-degree polynomial equation.     

Anionic polymerization of vinyl monomers with xanthates

The polymerization of vinyl monomers with various xanthates (potassium tert-butylxanthate, potassium benzylxanthate, zinc n-butylxanthate, etc.) were carried out at 0°C in dimethylformamide. N-Phenylmaleimide, acrylonitrile, methyl vinyl ketone, and methyl methacrylate were found to undergo polymerization with potassium tert-butylxanthate; however, styrene, methyl acrylate, and acrylamide were not polymerized with this xanthate. In the anionic polymerization of methyl vinyl ketone with potassium tert-butylxanthate, the rate of the polymerization was found to be proportional to the catalyst concentration and to the square of the monomer concentration. The activation energy of methyl vinyl ketone polymerization was 2.9 kcal/mole. In the polymerization, the order of monomer reactivity was as follows: N-phenylmaleimide > methyl vinyl ketone > acrylonitrile > methyl methacrylate. The initiation ability of xanthates increased with increasing basicity of the alkoxide group and with decreasing electronegativity of the metal ion in the series, lithium, sodium, and potassium tert-butylxanthate. The relative effects of the aprotic polar solvents on the reactivity of potassium tert-butylxanthate was also determined as follows: diethylene glycol dimethyl ether > dimethylsulfoxide > hexamethylphosphoramide > dimethylformamide > tetrahydrofuran (for methyl vinyl ketone); dimethyl sulfoxide > hexamethylphosphoramide > dimethylformamide ? diethylene glycol dimethyl ether (for acrylonitrile).     

Relative permittivity of the binary mixtures of 2-methoxyethanol with diethylene glycol,triethylene glycol,tetraethylene glycol,and polyethylene glycol 200 at various temperatures

Relative permittivities at T = (293.15, 298.15, and 303.15) K in the binary liquid mixtures of 2-methoxyethanol with diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol 200 have been measured over the entire mixture compositions. The relative permittivity deviations (Δε) were calculated from these experimental data. The results are discussed in terms of intermolecular interactions and structure of studied binary mixtures.     

Excess molar enthalpies of binary mixtures containing 2-decanone or dipentyl ether with long-chain n-alkanes at T = 298.15 K

Excess molar enthalpies (H^E) of binary mixtures of 2-decanone or dipentyl ether with n-alkanes, including n-dodecane, n-tetradecane, and n-hexadecane, were measured with an isothermal titration calorimeter (ITC) at T = 298.15 K under atmospheric pressure. All the measured H^E values are positive over the entire range of composition, indicating that all these mixing processes are endothermic. The H^E values varying with composition are found to be nearly symmetric for each binary system. It was also shown that the H^E values follow the order of n-hexadecane > n-tetradecane > n-dodecane at a given composition in either the 2-decanone or dipentyl ether binary systems. An empirical Redlich–Kister equation correlated quantitatively these new H^E data. The Peng–Robinson and the Patel–Teja equations of state, and the NRTL model were also applied to fit the H^E results. Among these tested correlative models, the Patel–Teja equation of state with two adjustable binary interaction parameters generally yielded the best representation.     

Polymerization of vinyl monomer with carbon disulfide–alkali metal complex

The reaction of carbon disulfide with one or two equivalents of alkali metal (potassium- or sodium) was carried out, and the deep red reaction mixture obtained only in diethylene glycol dimethyl ether. The polymerization of vinyl monomers with this reaction mixture was studied. The reaction mixtures of mono- and dialkali metal with carbon disulfide induced the polymerization of N-phenylmaleimide, methyl vinyl ketone, and acrylonitrile but did not induce the polymerization of methyl methacrylate and styrene. In the polymerization of acrylonitrile with this reaction mixture of carbon disulfide with monoalkali metal, the polymerization rate was found to be proportional to the initiator concentration and to the square of the monomer concentration. The activation energy was ?1.1 kcal/mole. Similar results were obtained in the case of carbon disulfide with dialkali metal. The polymer yield increased with increasing solvating power of solvents, i.e., diethylene glycol dimethyl ether, dimethyl sulfoxide, hexamethylphosphoramide, dimethylformamide, tetrahydrofuran. In the copolymerization of AN with MMA, the copolymer obtained consisted almost of AN units.     

Partition behaviour of benzoic acid in (water + n-dodecane) solutions at T = (293.15 and 298.15) K

The partition coefficients of benzoic acid in solutions of two immiscible solvents, water and n-dodecane, were measured at temperatures of (293.15 and 298.15) K. The experimental results indicated that at both temperatures the partition coefficients were not constant, but showed linear dependences on the concentration of benzoic acid in water. Dimerization of benzoic acid in n-dodecane and ionization in water were assumed based on the chemical theory and the experimental results verified this assumption quite well. Accordingly the association equilibrium constants of benzoic acid in n-dodecane were obtained by a linear regression. The regression results also showed that there was a very strong dimerization of benzoic acid in n-dodecane over the temperatures and concentration range investigated.     

Viscosity of binary mixtures of 2-ethoxyethanol with ethylene glycol,diethylene glycol,triethylene glycol and tetraethylene glycol systems at T = (293.15, 298.15 and 303.15) K

Viscosities, at T = 293.15, 298.15 and 303.15 K, in the binary mixtures of 2-ethoxyethanol with ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene glycol have been measured as a function of composition. From the experimental data the deviations in the viscosity have been calculated. The viscosity data, at T = 298.15 K, were correlated with equations of Hind et al., Grunberg and Nissan, and Frenkel. The results are discussed in terms of intermolecular interactions and structural properties of studied binary mixtures.     

A Comparative Study of (Poly)ether Adducts of Alkaline Earth Iodides – An Overview Including New Compounds

New homoligand and mixed‐ligand adducts of the heavier alkaline earth metal (Ca, Sr, Ba) halides with oxygen‐donor polyether ligands have been isolated and characterized and are compared with previously obtained compounds of the same class in order to give an overview on structures and properties. Homoligand halide adducts, discussed herein, are [CaI(DME)₃]I ( 1 ), trans‐[SrI₂(DME)₃] ( 2 ), trans‐[BaI₂(DME)₃] ( 3 ), (DME = ethylene glycol dimethyl ether), [CaI(diglyme)₂]I ( 4 ), cis‐[SrI₂(diglyme)₂] ( 5 ), trans‐[BaI₂(diglyme)₂] ( 6 ),(diglyme = diethylene glycol dimethyl ether, [SrI(triglyme)₂]I ( 7 ), and [BaI(triglyme)₂]I ( 8 ), (triglyme = triethylene glycol dimethyl ether). Introduction of the mono‐coordinating THF ligand (THF = tetrahydrofuran) in the coordination sphere of 1 , 2 , 3 , 4 allows the formation of the new mixed‐ligand compounds trans‐[CaI₂(DME)₂(THF)] ( 9 ), trans‐[SrI₂(DME)₂(THF)] ( 10 ), trans‐[BaI₂(DME)₂(THF)₂] ( 11 ), and trans‐[CaI₂(diglyme)₂(THF)₂] ( 12 ). These compounds were obtained from the metal halide salts in solution with pure or mixtures of ether solvents. While compounds 1 – 8 appear to be very stable and non‐reactive, adducts 9 – 12 present a comparable reactivity to the well known THF adducts [MI₂(thf)_n] (M = Ca, n = 4; Sr, Ba, n = 5).     

Extraction and carrier mediated transport of urea using noncyclic receptors through liquid membrane systems

Extraction and carrier mediated transport through bulk liquid membrane and supported liquid membrane systems have wide applications in separation technology. This paper highlights the use of six noncyclic receptors (podands) having variations in chain length and end group for the removal of urea using liquid membrane system. These receptors R_1, R_2, R_3, R_4, R_5, R₆ are diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, diethylene glycol dibenzoate, diethylene glycol, triethylene glycol and tetraethylene glycol respectively. The sequence of extraction and transport of urea by BLM system using various receptors is R₂ > R₃ > R₁ > R₄ > R₅ > R₆ and R₆ ≈ R₃ > R₅ > R₄ > R₁ > R₂ respectively. Receptor R₂ containing butyl end group is best extractant while receptor R₆ with flexible backbone is best carrier and this carrier efficiency is used to remove urea using BLM system from the feed phase by recyclization process up to 88.16%. The experimental results influenced by concentration of receptors and urea. Effect of time was also studied.     

Study of the binary mixtures of {monoglyme + (hexane,cyclohexane, octane,dodecane)} by ECM-average and PFP models

Excess molar volumes and excess permittivity of binary mixtures involving monoglyme and alkanes, such as n-hexane, cyclohexane, n-octane and n-dodecane, were calculated from density and relative permittivity measurements for the entire composition range at several temperatures (288.15, 298.15 and 308.15) K and atmospheric pressure. The excess permittivity was calculated on the basis of a recent definition considering the ideal volume fraction. Empirical equations for describing the experimental data in terms of temperature and concentration are given. The experimental values of permittivity have been compared with those estimated by well-known models from literature. The results have indicated that better predictions are obtained when the volume change on mixing is incorporated in these calculations. The contribution of interactions to the excess permittivity was analysed by means of the ECM-average model. The Prigogine–Flory–Patterson (PFP) theory of the thermodynamics of solutions was used to shed light on the contribution of interactions to the excess molar volume. The work concludes with an interpretation of the information given by the theoretical models and the behaviour of both excess magnitudes.     

Formation of diethylene glycol as a side reaction during production of polyethylene terephthalate

Polymers of poly(ethylene terephthalate) (PET) always contain a certain amount of incorporated diethylene glycol (DEG), substituting the incorporated glycol. DEG is formed in a side reaction during the ester interchange of dimethyl terephthalate (DMT) with ethylene glycol or during direct esterification of terephthalic acid with ethylene glycol, and to a smaller extent during the polycondensation of the low-molecular material. DEG is formed via an unusual type of reaction: ester + alcohol → ether + acid. Some evidence of this type of reaction is given by the formation of dioxane in low molecular PET and of methyl Cellosolve and methyl carbitol during the ester interchange of DMT with ethylene glycol and diethylene glycol, respectively. The strongest support for this type of reaction, however, was obtained from kinetic data. Polyesters of low molecular weight with OH group contents ranging from 3 to 0.5 mole/kg were heated at 270°C in sealed tubes for 1–7 hr. The kinetic equation for the proposed reaction is: d[DEG]/dt = k[OH] [ester]. With the aid of one rate constant the formation of DEG in all esters could be described.     

Reductive isomierization of icosahedral metallocarbaboranes

When reduced over a sodium amalgam, a variety of icosahedral metal-locarbaboranes are found to isomerize under mild experimental conditions. Complexes containing second-row transition metals (Ru and Rh) rearrange rapidly at room temperature, but even cobaltacarbaboranes will isomerize in refluxing 1,2-dimethoxyethane (85°C) or diethylene glycol dimethyl ether (162°C). The direction of rearrangement is that found in straight thermally-induced isomerizations.