Synthesis and metallophilic properties of troponoid thiocrown ethers

A new class of ionophores with troponoid and thiocrown ether units was prepared. Cation-binding properties of troponoid dithiocrown ethers were characterized using UV and NMR spectroscopies. They have affinity with metal ions; in particular, they showed high affinity with Hg2+. Transport of Hg2+ through a CHCl3 liquid membrane with troponoid dithiocrown ethers was examined in a U-type cell. From an aqueous solution of HgCl2 and CuCl2, Hg2+ is transferred selectively and smoothly, while the Cu2+ remained quantitatively in the original solution. The cavity size of dithiocrown ethers is one of the requirements for effective extraction and transport of Hg2+. However, derivatives with a smaller cavity still extract and transport Hg2+. A polymer-supported troponoid dithiocrown ether was prepared to transport Hg2+ effectively and repeatedly. Comparing the troponoid dithiocrown ether with the benzenoid dithiocrown ether with a similar cavity size, the former was more effective for the transport of Hg2+. It is proposed that the tropone ring assisted the release of Hg2+ from the complex by Coulomb repulsion between the protonated tropone ring and Hg2+.

Miscibility studies of the blends of chitosan with some cellulose ethers

The polymeric films have been prepared based on blends of chitosan with two cellulose ethers-hydroxypropylmethylcellulose and methylcellulose by casting from acetic acid solutions. The films were transparent and brittle in a dry state but an immersion of the samples in deionized water for over 24 h leads to their disintegration or partial dissolution. The miscibility of the polymers in the blends has been assessed by infrared spectroscopy, wide-angle X-ray diffraction, scanning electron microscopy and thermal gravimetric analysis. It was shown that although weak hydrogen bonding exists between the polymer functional groups the blends are not fully miscible in a dry state.

Gas-phase ion - Molecule reactions of neutral C-60 with the plasmas of alkyl methyl ethers and primary alcohols

The gas-phase ion-molecule reactions of C-60 with the methoxymethyl ion [CH3O=CH2](+) and the 1-hydroxyethyl ion [CH3CH=OH](+) generated under the self-chemical-ionization (self-CI) conditions of alkyl methyl ethers and primary alcohols were studied in the ion source of a mass spectrometer. The adduct ions [C60C2H5O](+) and protonated molecules [C60H](+) were observed as the major products of C-60 with the plasma of alkyl methyl ethers. On the contrary, the reactions of C-60 With the plasmas of primary alcohols produced few corresponding adduct ions. The AM1 semiempirical molecular orbital calculations were carried out on 14 possible structures. The calculated results showed that the most stable structure among the possible isomers of [C60C2H5O](+) is the [3+2] cycloadduct. According to experimental and theoretical results, the pathway for the formation of the adduct was presented.

Gas-phase ion-molecule reactions of C-60 with methyl ethers CH3OCnH2n+1

Gas-phase ion-molecule reactions of buckminsterfullerene (C-60) with the ion systems generated from the self-chemical-ionization of alkyl methyl ethers(CH3OCnH2n+1, n =2 , 3, 4) were studied in the ion source of a mass spectrometer. The adduct cation [C60C2H5O](+) and protonated molecular ion [C60H](+) were observed as the major products, The former was produced by the reactions.of C-60 with the methoxymethyl ion [CH3O = CH2](+) , the latter corresponded to the proton transfer reactions from the protonated alkyl methyl ethers to C60 It is suggested that the [3+2] cycloadduct is the most favorable structure among the probable isomers with special chemical properties, Our investigation provides the guidance for the synthesis of this compound in condensed phase.

Gas-phase ion-molecule reactions of neutral C-60 with alkyl methyl ethers under chemical ionization conditions

Gas-phase ion-molecule reactions of buckminsterfullerene (C-60) with the ion systems generated from the self-chemical ionization of alkyl methyl ethers (CH3OR, R = n-C2H5, n-C3H7, n-C4H9) were studied in the ion source of a mass spectrometer. The adduct cation [C60C2H5O](+) and protonated molecule [C60H](+) were observed as the major products. The former adduct ion was produced by the reactions of C-60 with the methoxymethyl ion [CH3OCH2](+), and the latter resulted from the proton transfer reactions from protonated alkyl methyl ethers to C-60 It is suggested that the [3+2] cycloadduct to a 6-6 bond of C-60 (a C-C bond common to two annulated six-membered rings) is the most favorable structure among the probable isomers of [C60C2H5O](+). (C) 1998 John Wiley & Sons, Ltd.

CRYSTALLINITY OF UNIFORM OLIGO(OXYETHYLENE) MONO-N-ALKYL ETHERS STUDIED BY X-RAY-DIFFRACTION AND DIFFERENTIAL SCANNING CALORIMETRY

The crystallinity of two series of uniform oligo(oxyethylene) mono-n-alkyl ethers has been investigated: alpha-alkyl,omega-hydroxyoligo(oxyethylene)s, H(CH2)n(OCH2CH2)mOH, and alpha-alkyl,omega-methoxyoligo(oxyethylene)s, H(CH2)n(OCH2CH2)mOCH3. The hydroxy-ended oligomers formed bilayer crystals, and the methoxy-ended oligomers formed monolayer crystals. The helical oxyethylene blocks were oriented normal to the layer-crystal end-group plane, whilst the trans-planar alkyl blocks were generally tilted at an angle delta = 60-degrees. The melting temperature and enthalpy of fusion were higher for hydroxy-ended oligomers than for corresponding methoxy-ended oligomers.

Non-ideal behaviour of a room temperature ionic liquid in an alkoxyethanol or poly ethers at T = (298.15 to 318.15) K

Non-ideal behaviour of 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6] in ethylene glycol monomethyl ether; CH3OCH2CH2OH (EGMME), ethylene glycol dimethyl ether; CH3OCH2CH2OCH3 (EGDME) and diethylene glycol dimethyl ether; CH3(OCH2CH2)2OCH3 (DEGDME) have been investigated over the whole composition range at T = (298.15 to 318.15) K. To gain insight into the mixing behaviour, results of density measurements were used to estimate excess molar volumes, image, apparent molar volumes, Vphi,i, partial molar volumes, image, excess partial molar volumes, image, and their limiting values at infinite dilution, image, image, and image, respectively. Volumetric results have been analyzed in the light of Prigogine–Flory–Patterson (PFP) statistical mechanical theory. Measurements of refractive indices n were also performed for all the binary mixtures over whole composition range at T = 298.15 K. Deviations in refractive indices ?phin and the deviation of molar refraction ?xR have been calculated from experimental data. Refractive indices results have been correlated with volumetric results and have been interpreted in terms of molecular interactions. Excess properties are fitted to the Redlich–Kister polynomial equation to obtain the binary coefficients and the standard errors.

Rheological destructuring of aqueous gels composed of cellulose ethers following storage in the presence of redox agents

Despite their widespread use, there is a paucity of information concerning the effect of storage on the rheological properties of pharmaceutical gels that contain organic and inorganic additives. Therefore, this study examined the effect of storage (1 month at either 4 or 37 degrees C) on the rheological and mechanical properties of gels composed of either hydroxypropylmethylcellulose (3-5% w/w, HPMC) or hydroxyethylcellulose (3-5% w/w, HEC) and containing or devoid of dispersed organic (tetracycline hydrochloride 2% w/w) or inorganic (iron oxide 0.1% w/w) agents. The mechanical properties were measured using texture profile analysis whereas the rheological properties were analyzed using continuous shear rheometry and modeled using the Power Law model. All formulations exhibited pseudoplastic flow with minimal thixotropy. Increasing polymer concentration (3-5% w/w) significantly increased the consistency, hardness, compressibility, and adhesiveness of the formulations due to increased polymer chain entanglement. Following storage (I month at 4 and 37 degrees C) the consistency and mechanical properties of additive free HPMC gets (but not HEC gels) increased, due to the time-dependent development of polymer chain entanglements. Incorporation of tetracycline hydrochloride significantly decreased and increased the rheological and mechanical properties of HPMC and HEC gels, respectively. Conversely, the incorporation of iron oxide did not affect these properties. Following storage, the rheological and mechanical properties of HPMC and HEC formulations were markedly compromised. This effect was greater following storage at 37 than at 4 degrees C and, additionally, greater in the presence of tetracycline hydrochloride than iron oxide. It is suggested that the loss of rheological/mechanical structure was due to chain depolymerization, facilitated by the redox properties of tetracycline hydrochloride and iron oxide. These observations have direct implications for the design and formulation of gels containing an active pharmaceutical ingredient. (c) 2005 Wiley Periodicals, Inc.

Base-Mediated Cascade Rearrangements of Aryl-Substituted Diallyl Ethers

Two base-mediated cascade rearrangement reactions of diallyl ethers were developed leading to selective [2,3]-Wittig–oxy-Cope and isomerization–Claisen rearrangements. Both diaryl and arylsilyl-substituted 1,3-substituted propenyl substrates were examined, and each exhibits unique reactivity and different reaction pathways. Detailed mechanistic and computational analysis was conducted, which demonstrated that the role of the base and solvent was key to the reactivity and selectivity observed. Crossover experiments also suggest that these reactions proceed with a certain degree of dissociation, and the mechanistic pathway is highly complex with multiple competing routes.

Biomass-derived Oxymethylene Ethers as Diesel Additives: A Thermodynamic Analysis

Conversion of biomass for production of liquid fuels can help in reducing the greenhouse gas (GHG) emissions which are predominantly generated by combustion of fossil fuels. Adding oxymethylene ethers (OMEs) in conventional diesel fuel has the potential to reduce soot formation during the combustion in a diesel engine. OMEs are downstream products of syngas, which can be generated by the gasification of biomass. In this research, a thermodynamic analysis has been conducted through development of data intensive process models of all the unit operations involved in production of OMEs from biomass. Based on the developed model, the key process parameters affecting the OMEs production including equivalence ratio, H2/CO ratio, and extra water flow rate were identified. This was followed by development of an optimal process design for high OMEs production. It was found that for a fluidized bed gasifier with heat capacity of 28 MW, the conditions for highest OMEs production are at an air amount of 317 tonne/day, at H2/CO ratio of 2.1, and without extra water injection. At this level, the total OMEs production is 55 tonne/day (13 tonne/day OME3 and 9 tonne/day OME4). This model would further be used in a techno-economic assessment study of the whole biomass conversion chain to determine the most attractive pathways.

Assessing the environmental fate of selected polybrominated diphenyl ethers in the region surrounding the Zhuoshui River of Taiwan based on an Equilibrium Constant fugacity model

Polybrominated diphenyl ethers (PBDEs) are a group of flame retardants that have been in use since the 1970s. They are included in the list of hazardous substances known as persistent organic pollutants (POPs) because they are extremely hazardous to the environment and human health. PBDEs have been extensively used in industry and manufacturing in Taiwan, thus its citizens are at high risk of exposure to these chemicals.
An assessment of the environmental fate of these compounds in the Zhuoshui river and Changhua County regions of western Taiwan, and also including the adjacent area of the Taiwan Strait, was conducted for three high risk congeners, BDE-47, -99 and -209, to obtain information regarding the partitioning, advection, transfer and long range transport potential of the PBDEs in order to identify the level of risk posed by the pollutants in this region.
The results indicate that large amounts of PBDEs presently reside in all model compartments – air, soil, water, and sediment – with particularly high levels found in air and especially in sediment. The high levels found in sediment, particularly for BDE-209, are significant, since there is the threat of these pollutants entering the food chain, either directly through benthic feeding, or through resuspension and subsequent feeding in the pelagic region of the water column which is a distinct possibility in the strong currents found within the Taiwan Strait. Another important result is that a substantial portion of emissions leave the model domain directly through advection, particularly for BDE-47 (58%) and BDE-209 (75%), thus posing a risk to adjacent communities.
Model results were generally in reasonable agreement with available measured concentrations. In air, model concentrations are in reasonably good agreement with available measured values. For both BDE-47 and -99, model concentrations are a factor of 2-3 higher and BDE-209 within the range of measured values. In soil, model results are somewhat less than measured values. In sediment, model results are at the high end of measured values.