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We employ dielectric spectroscopy and molecular dynamic simulations to investigate the dipolar dynamics in the orientationally disordered solid phase of (1,1,2,2)tetrachloroethane. Three distinct orientational dynamics are observed as separate dielectric loss features, all characterized by a simply activated temperature dependence. The slower process, associated to a glassy transition at 156 ± 1 K, corresponds to a cooperative motion by which each molecule rotates by 180. around the molecular symmetry axis through an intermediate state in which the symmetry axis is oriented roughly orthogonally to the initial and final states. Of the other two dipolar relaxations, the intermediate one is the Johari-Goldstein precursor relaxation of the cooperative dynamics, while the fastest process corresponds to an orientational fluctuation of single molecules into a higher-energy orientation. The Kirkwood correlation factor of the cooperative relaxation is of the order of one tenth, indicating that the molecular dipoles maintain on average a strong antiparallel alignment during their collective motion. These findings show that the combination of dielectric spectroscopy and molecular simulations allows studying in great detail the orientational dynamics in molecular solids. [ABSTRACT FROM AUTHOR]

A thorough characterization of the γ, β, and glass phases of deuterated 1,1,2,2 tetrachloroethane (C2D2Cl4) via nuclear quadrupole resonance and Molecular Dynamic Simulations (MDSs) is reported. The presence of molecular reorientations was experimentally observed in the glass phase and in the β phase. In the β phase, and from MDS, these reorientations are attributed to two possible movements, i.e., a 180? reorientation around the C2 molecular symmetry axis and a reorientation of the molecule between two non-equivalent positions. In the glass phase, the spin-lattice relaxation time T¹ is of the order of 16 times lower than in the crystalline phase and varies as T-1 below 100 K in good agreement with the strong quadrupolar relaxation observed in amorphous materials and in the glassy state of molecular organic systems. The activation energy of molecular reorientations in the glass phase (19 kJ/mol) is comparable to that observed in the glassy crystal of a "molecular cousin" compound, Freon 112 (C2F2Cl4), for the secondary β-relaxation. Moreover, the on-site orientational motion of tetrachloroethane molecules offers a new indirect evidence of the prominent role of such orientational disorder in glassy dynamics. [ABSTRACT FROM AUTHOR]

Herein, we report a simple method for the preparation of cross-linked polymer of intrinsic microporosity (PIM-1)/Materials Institute Lavoisier chromium (III) terephthalate [MIL-101(Cr)] monoliths which involves direct impregnation of PIM-1 with MIL-101(Cr) powder by physical mixing in tetrachloroethane solvent. This procedure yields monoliths with high metal-organic framework (MOF) loading weight percentages of up to 80 wt% of MIL-101 powder with little loss of composite mechanical strength. From the nitrogen adsorption isotherms, it was observed that the PIM-1/80 wt% MIL-101(Cr) had good retention of MOF filler surface area and accessibility of its micropores with nearly no pore blocking effects. The hydrogen adsorption was also not far from the estimated hydrogen uptake capacity based on the MIL-101 weight percentage estimation. As a consequence of the highly porous nature of the hybrid material, PIM-1/MIL-101(Cr) composite has been considered as a promising material for inclusion in hybrid hydrogen storage cylinders. Moreover, these composites provided better handling compared to the crystalline powder MOFs without compromising the properties of MOF. [ABSTRACT FROM AUTHOR]

An efficient and facile method has been developed for the synthesis of alkyl bromides from various alcohols under mild conditions using a triphenylphosphine (PPh3) /1,2-dibromotetrachloroethane (DBTCE) complex in excellent yields and very short time (5 min). This method can also be applied for the transformation of chiral alcohols to their corresponding bromides in very high enantiomeric excess. The PPh3 /DBTCE complex is also successfully applied to ring-opening reactions of cyclic ethers in mild conditions. Esterification, amidation, and formation of acid anhydrides under very mild experimental conditions are also successfully accomplished by following a modification of the Appel reaction protocol in this work. [ABSTRACT FROM AUTHOR]

Abstract Coupling in situ thermal treatment (ISTT) with microbial reductive dechlorination (MRD) has the potential to enhance contaminant degradation and reduce cleanup costs compared to conventional standalone remediation technologies. Impacts of low-temperature ISTT on Dehalococcoides mccartyi (Dhc), a relevant species in the anaerobic degradation of cis -1,2-dichloroethene (cis -DCE) and vinyl chloride (VC) to nontoxic ethene, were assessed in sand-packed columns under dynamic flow conditions. Dissolved tetrachloroethene (PCE; 258 ± 46 μM) was introduced to identical columns bioaugmented with the PCE-to-ethene dechlorinating consortium KB-1®. Initial column temperatures represented a typical aquifer (15 °C) or a site undergoing low-temperature ISTT (35 °C), and were subsequently increased to 35 and 74 °C, respectively, to assess temperature impacts on reductive dechlorination activity. In the 15 °C column, PCE was transformed primarily to cis -DCE (159 ± 2 μM), which was further degraded to VC (164 ± 3 μM) and ethene (30 ± 0 μM) within 17 pore volumes (PVs) after the temperature was increased to 35 °C. Regardless of the initial column temperature, ethene constituted >50 mol% of effluent degradation products in both columns after 73–74 PVs at 35 °C, indicating that MRD performance was greatly improved under low-temperature ISTT conditions. Increasing the temperature of the column initially at 35 °C resulted in continued VC and ethene production until a temperature of approximately 43 °C was reached, at which point Dhc activity substantially decreased. The abundance of the vcrA reductive dehalogenase gene exceeded that of the bvcA gene by 1–2.5 orders of magnitude at 15 °C, but this relationship inversed at temperatures >35 °C, suggesting Dhc strain-specific responses to temperature. These findings demonstrate improved MRD performance with low-temperature thermal treatment and emphasize potential synergistic effects at sites undergoing ISTT. Graphical abstract Image 1 Highlights • Microbial reductive dechlorination of PCE was enhanced at temperatures up to 43 °C. • Impacts of heating on Dhc dechlorination activity were strain-specific. • Dhc tolerates higher temperatures in flowing systems compared to batch reactors. • Ethene formation was not sensitive to the order of thermal-bio remedy application. [ABSTRACT FROM AUTHOR]

Abstract: Effect of H2 amount on the activity and selectivity of Chevron-Phillips trimerization system, i.e., chromium(III) tris(2-ethylhexanoate)/2,5-dimethylpyrrole/triethylaluminum (TEA)/tetrachloroethane (TCE), was examined. In this regard, in addition to catalytic ingredients and ethylene monomer, 2.5 and 5 bar H2 were utilized in the oligomerization reactor and the reaction results were compared with those without H2. Results showed that addition of hydrogen has a remarkable effect on polymer formation and catalyst activity so that 147% decrease in polymer formation and 38% increase in activity were observed upon addition of 5 bar H2. However, its effect on 1-hexene selectivity was not pronounced. Then, molecular modeling with DFT method was employed to simulate oligomerization process in molecular level. Energy results revealed that formation of 1-hexene has less energy barrier than the formation of 1-butene and 1-octene which confirms higher selectivity of Chevron-Phillips system toward 1-hexene formation. Furthermore, interaction of hydrogen with catalytic active center was studied via hydrogenolysis of metalacycles. Energy results revealed that it is energetically a facile process so that the bigger the circle, the easier hydrogenolysis.Graphical abstract: [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and characterization of a new type of a highly conjugated heterocyclic π‐chromophore, consisting of a central triphenylene core fused with three perylene monoimide units (star‐shaped molecules), is described. By judicious bay functionalization with tert‐butylphenoxy substituents, aggregation was completely prevented by using 1,1,2,2‐tetrachloroethane, allowing for a straightforward purification and, for the very first time, the complete separation of the constitutional isomers by HPLC. Both isomers can be easily distinguished by means of several conventional spectroscopic techniques. Furthermore, we have illustrated the absence of supramolecular aggregates and enhanced processability by noncovalent functionalization of graphene substrates, showing an outstanding homogeneity and demonstrating a different doping behavior in both isomers, making it possible to distinguish them by Raman spectroscopy. [ABSTRACT FROM AUTHOR]

BACKGROUND 1,1,2,2-tetrachloroethane (TeCA) has been generally considered as non-biodegradable under aerobic conditions, while its complete biodegradation was reported with microbial consortia growing anaerobically. This study describes TeCA aerobic co-metabolic degradation by the propanotroph Rhodococcus aetherivorans strain TPA isolated from a TeCA-degrading consortium. RESULTS R. aetherivorans TPA was able to grow on aliphatic hydrocarbons from propane to pentane and on gaseous n-alkane metabolic intermediates. The Michaelis-Menten model allowed a satisfactory fit of the TPA propane utilization rates under resting cell conditions, while the TeCA degradation rates were successfully interpolated with Andrew's inhibition model. A significant propane-TeCA mutual inhibition was observed, although the results did not allow distinguishing between competitive and non-competitive inhibition. Among different bioreactor options for the on-site bioremediation of TeCA-contaminated groundwater, a single suspended-cell continuous stirred-tank reactor (CSTR) appeared to be the optimal one. CONCLUSIONS This study provides for the first time the kinetic and microbiological characterization of a bacterial strain capable of degrading TeCA under aerobic conditions. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The development and validation of a novel kinetic model for the chlorination of 1,2-dichloroethane to ultimately hexachloroethane catalyzed by blue light are presented. A factor ( X m) related to the chlorination depth was introduced into the kinetics model, and the results showed that the dynamic features of the photo-chlorination are better predicted by the modified model than by the conventional one. Furthermore, to enhance the selectivity towards tetrachloroethane and pentachloroethane, a novel reactive distillation with side-reactor configuration (SRC) for the photo-chlorination process was proposed. In order to demonstrate the technical feasibility of the process, semi-batch SRC experiments on the laboratory scale were carried out. Up to 96.5 wt % of tetrachloroethane and pentachloroethane with molar ratios varying from 7 to 0.7 over time were obtained in the bottom product. [ABSTRACT FROM AUTHOR]

The host-guest chemistry of cycloparaphenylenes (CPPs) of different sizes is described. [ n]CPPs ( n=5, 6, 7, 8, and 10) selectively interact with [ n+5]CPPs, forming complexes [ n+5]CPP⊃[ n]CPP, which are the shortest double-walled armchair carbon nanotubes. The size selectivity is dictated by the difference in diameters of the CPPs (that is, 0.34-0.35 nm), which maximizes attractive van der Waals interactions. Theoretical calculations suggest that the orbital energies of the CPPs become perturbed upon complex formation, and orbital mixing between the two CPPs is predicted for large CPP pairs. The association constants in 1,1,2,2-[D2]tetrachloroethane, estimated by 1H NMR titration, are approximately 103 mol L−1 at 50 °C. Van't Hoff plot analysis reveals that complexation is driven mainly by entropy owing to desolvation of the CPPs. [13]CPP also forms a complex with [4]cyclo-2,7-pyrenylene ([4]CPY), which is a π-extended [8]CPP. Theoretical calculations suggest that the formation of [13]CPP⊃[4]CPY is more exothermic than that of [13]CPP⊃[8]CPP. A ternary complex, [15]CPP⊃[10]CPP⊃C60, is also formed by mixing [15]CPP and [10]CPP⊃C60. [ABSTRACT FROM AUTHOR]

The surface heterogeneous atoms of carbonaceous materials (CMs) play an important role in adsorption of organic pollutants. However, little is known about the surface heterogeneous atoms of CMs might generate different effect on adsorption of hydrophobic organic compounds by porous carbonaceous materials — activated carbons (ACs) and non-porous carbonaceous materials (NPCMs). In this study, we observed that the surface oxygen and nitrogen atoms could decrease the adsorption affinity of both ACs and NPCMs for 1,1,2,2-tetrachloroethane (TeCA), but the degree of decreasing effects were very different. The increasing content of surface oxygen and nitrogen ([O + N]) caused a sharper decrease in adsorption affinity of ACs (slope of lg ( k d / SA ) vs [O + N]: −0.098∼-0.16) than that of NPCMs (slope of lg ( k d / SA ) vs [O + N]: −0.025∼-0.059) for TeCA. It was due to the water cluster formed by the surface hydrophilic atoms that could block the micropores and generate massive invalid adsorption sites in the micropores of ACs, while the water cluster only occupied the surface adsorption sites of NPCMs. Furthermore, with the increasing concentration of dissolved TeCA, the effect of surface area on adsorption affinity of NPCMs for TeCA kept constant while the effect of [O + N] decreased due to the competitive adsorption between water molecule and TeCA on the surface of NPCMs, meanwhile, both the effects of micropore volume and [O + N] on adsorption affinity of ACs for TeCA were decreased due to the mechanism of micropore volume filling. These findings are valuable for providing a deep insight into the adsorption mechanisms of CMs for TeCA. [ABSTRACT FROM AUTHOR]

Microbial degradation of 1,1,2,2-tetrachloroethane has been rarely analysed under aerobic conditions. In this work, the catabolic potential of a TeCA-degrading aerobic propanotroph consortium (C 2 ) and the optimal bioreactor configuration for an on-site TeCA-bioremediation strategy with C 2 were defined. More specifically, the diversity of alkane-oxidizing bacteria in C 2 was assessed by means of clone libraries of genes coding for alkane monooxygenases (MOs) of different families (AlkB-like alkane hydroxylase, soluble di-iron MO and cytochromes P450). A large number of alkane MO sequences retrieved in this study showed the highest similarity with reference sequences belonging to Rhodococcus genus, suggesting a key role of this genus in TeCA/propane co-metabolism, while the remaining alkane MO sequences were mainly attributed to other Actinobacteria , to Bradhyrizobiaceae , and Cupriavidus genus. Further, the feasibility of an on-site TeCA bioremediation strategy with C 2 was evaluated by simulating a continuous-flow aerobic co-metabolic process with different bioreactor configurations. Our results show that the configuration with a suspended-cell continuous stirred-tank reactor (CSTR) followed by a suspended-cell plug-flow reactor (PFR) was the one giving the best performance with consortium C 2 . [ABSTRACT FROM AUTHOR]

Two well-known microextraction methods, dispersive liquid–liquid microextraction (DLLME) and solid–phase microextraction (SPME), were combined, resulting in as an encouraging method. The method, named DLLME–SPME, was performed based on total vaporization technique. For the DLLME step, 1,1,2,2-tetrachloroethane and acetonitrile were used as extraction and disperser solvents, respectively. Halloysite nanotubes–titanium dioxide was used as the fiber coating in the SPME step. The method was applied for the extraction of diazinon and parathion (as the test compounds) in environmental water samples and fruit juices, and gas chromatography–corona discharge ion mobility spectrometry was used as the determination apparatus. Desorption temperature and time, extraction temperature and time, and the volume of the extracting solvent in the DLLME step were optimized as the effective parameters on the extraction efficiency. The relative standard deviations (RSDs) of intra-day were found to be 4–7% and 6–8% for diazinon and parathion, respectively. Also, the RSDs of inter-day were 7–9% and 8–10% for diazinon and parathion, respectively. The limits of quantification and detection were obtained to be 0.015 and 0.005 μg L −1 for diazinon, and 0.020 and 0.007 μg L −1 for parathion. A good linearity range (r 2 ˃ 0.993) was obtained in the range of 0.015–3.000 and 0.020–3.000 μg L −1 for diazinon and parathion, respectively. The high enrichment factors were obtained as 3150 and 2965 for diazinon and parathion, respectively. This method showed high sensitivity with good recovery values (between 87 and 99%) for the extraction of target analytes in the real samples. Overall, the results revealed that the developed DLLME–SPME method had better extraction efficiency than DLLME and SPME alone. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) and reduced graphene oxide (RGO) materials contain a variety of surface O-functional groups that are chemically reactive. When released into the environment these materials may significantly affect the abiotic transformation of organic contaminants, and therefore, may alter their fate and risks. We found that two GO and five RGO materials that varied in C/O ratio, hydrophobicity, and type/distribution of surface O-functionality all had catalytic effects on the dehydrochlorination of 1,1,2,2-tetrachloroethane (TeCA). Even though the catalytic effects of the materials originated from their deprotonated surface O-functional groups, which served as conjugated bases to catalyze the reaction, the catalytic efficiencies of the materials did not correlate strongly with their surface O contents. The spectroscopic evidence (X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy), surface charge data, and adsorption experiments demonstrated that the catalytic efficiencies of the GO/RGO materials were controlled by a complex interplay of the type and distribution of surface O-functionality, as well as adsorption affinity of the materials. Both Ca 2+ and Mg 2+ inhibited the catalytic efficiency of the materials by binding to the surface O-functional groups, and consequently, decreasing the basicity of the functional groups. At an environmentally relevant concentration of 10 mg/L, Suwannee River humic acid (used as a model dissolved organic matter) alone had little effect on the dehydrochlorination of TeCA. However, it could inhibit the catalytic efficiency of the GO/RGO materials by coating on their surface and thus, decreasing the adsorption affinity of these materials for TeCA. The findings further underline the potentially important impacts of nanomaterials on contaminant fate and effects in the environment. [ABSTRACT FROM AUTHOR]

The ring-opening polymerization (ROP) of cyclic butylene terephthalate oligomers (cBT) using an aluminum salen catalyst was investigated. The kinetic analysis of the ROP of cBT in tetrachloroethane (TCE) revealed a first-order dependence of the rate constant in catalyst as well as monomer concentration. Comparison with the ROP in other solvents showed that TCE significantly retards the reaction by short-term reversible catalyst deactivation and by long-term permanent deactivation. The apparent activation energy for the ROP of cBT and ε-caprolactone (CL) were determined independently, and the difference in reactivity was used to investigate the possibility to synthesize blocky copolymers. Sequence distribution analysis of the copolymers obtained over a period of time from a single feed copolymerization revealed that over the full reaction range the degree of randomness was high. A sequential feed approach, in which CL was added after the polymerization of cBT was completed, showed that the propagation reaction was not fast enough to avoid transesterification, yielding copolymers with an increasing degree of randomness over time. Additionally, the copolymerization of cBT with ω-pentadecalactone (PDL) was performed in bulk at temperatures above the crystallization temperature of poly(butylene terephthalate) (PBT), yielding random copolymers over the full composition range between polypentadecalactone (PPDL) and PBT. Copolymerizations using aluminum salen as catalyst were rapid and high molecular weights could be achieved. The melting temperature of both PPDL and PBT decreased upon the introduction of either counit, reaching a eutectic point between 50 and 70 mol % PDL. Furthermore, a combination of thermal analysis and X-ray diffraction shows that PDL units are fully excluded from the PBT crystal lattice, while butylene terephthalate units are partially incorporated into the PPDL crystal lattice. [ABSTRACT FROM AUTHOR]

The crystal structure of the organic semiconductor 9,10-diphenylanthracene (DPA) has been studied by single-crystal X-ray diffraction at variable pressure up to 3 GPa. Under ambient conditions and in the presence of 1,1,2,2-tetrachloroethane, the material invariably crystallises in an unsolvated form, in the space group C2/c, with Z′ = 1/2, as reported in the literature. As pressure is increased to a modest 0.5 GPa, crystallisation occurs in the form of a newly discovered solvate with a 1 : 2 DPA–tetrachloroethane stoichiometry, with the space group P21/c. A theoretical analysis by the PIXEL method with energy partitioning into Coulombic polarisation and dispersion terms reveals that the solvated and unsolvated structures have in common two basic packing motifs for the DPA molecule, one with linear interlocking and one with a T-shaped arrangement in a quincunx fashion. The solvent is enclosed in a cage and interacts with the DPA molecule by a very strong dispersive component of 44 kJ mol−1. Monte Carlo simulations show that the mobility of the solvent in its cage would be extremely reduced even under ambient conditions, ruling out a mechanism of solvate formation and subsequent release. According to a structure-oriented perspective, the kinetics of the process could then be such that the nucleating system at ambient pressure separates out the solvent, while a 0.5 GPa pressure provides a solute–solvent grip that forces cocrystallisation, in agreement with both experiments and simulations. Even in the absence of experimental or computational proof of the thermodynamic stability of the solvate at high pressure, this appears to be a plausible and sensible case scenario in its own right. [ABSTRACT FROM AUTHOR]

Bioremediation strategies, including bioaugmentation with chlorinated ethene-degrading enrichment cultures, have been successfully applied in the cleanup of subsurface environments contaminated with tetrachloroethene (PCE) and/or trichloroethene (TCE). However, these compounds are frequently found in the environment as components of mixtures that may also contain chlorinated ethanes and methanes. Under these conditions, the implementation of bioremediation may be complicated by inhibition effects, particularly when multiple dehalorespirers are present. We investigated the ability of the 1,1,2,2-tetrachloroethane (TeCA)-dechlorinating culture WBC-2 to biotransform TeCA alone, or a mixture of TeCA plus PCE and carbon tetrachloride (CT), in microcosms. The microcosms contained electron donors provided to biostimulate the added culture and sediment collected from a wetland where numerous “hotspots” of contamination with chlorinated solvent mixtures exist. The dominant TeCA biodegradation mechanism mediated by the WBC-2 culture in the microcosms was different in the presence of these wetland sediments than in the sediment-free enrichment culture or in previous WBC-2 bioaugmented microcosms and column tests conducted with wetland sediment collected at nearby sites. The co-contaminants and their daughter products also inhibited TeCA biodegradation by WBC-2. These results highlight the need to conduct biodegradability assays at new sites, particularly when multiple contaminants and dehalorespiring populations are present. [ABSTRACT FROM AUTHOR]

The compositions of bacterial community in one site contaminated with PCE/TCE after the slow polycolloid-releasing substrate (SPRS) (contained vegetable oil, cane molasses, and surfactants) addition were analyzed. Results show that SPRS caused a rapid enhancement of reductive dechlorination of TCE. The transformation of PCE/TCE into ethene was observed after 20 days of operation. To compare the change of bacterial communities before and after SPRS addition, 16S rRNA amplicon sequencing using the metagenome analysis was performed. Results demonstrated the detection of the increased amounts of Dehalogenimonas by 2.2-fold, Pseudomonas by 3.4-fold and Sulfuricurvum by 4-fold with the analysis of the ribosomal database project (RDP). Metagenomic DNA was extracted from PCE/TCE-contaminated groundwater after SPRS addition, and subjected to sequencing. Results obtained from metagenomic sequencing indicate that genes from Dehalococcoides mccartyi was ranked as the second abundant bacteria among all of the detected bacteria via the analysis of the lowest common ancestor (LCA). Abundance of these bacterial groups, as shown above suggests their role in TCE biodegradation. Functional analysis of the metagenome, with the specific reference to chloroalkane and chloroalkene degradation, revealed the presence of some genes responsible for TCE biodegradation. Overall, results of this study provided new insights for a better understanding of the potential of biostimulation on TCE-contaminated sites. [ABSTRACT FROM AUTHOR]

A fast and reliable approach for the measurement of sub parts-per-billion levels of targeted chlorinated compounds like tetrachloroethane, hexachloroethane, hexachlorobutadiene, pentachlorobenzene, and hexachlorobenzene in various water matrices such as waste water is described. The method employed a novel piston-cylinder-based micro liquid-liquid extraction technique using hexane as an extraction solvent. The device, known commercially as the MIXXOR, substantially accelerates extraction time by a factor of more than 100 times and reduces solvent consumption by a factor of 25 times when compared with the solvent extraction technique using wrist-action mechanical agitation. A recently introduced 6% cyanopropylphenyl -94% dimethylpolysiloxane capillary column offering a high degree of inertness was used for the separation of the analytes. A quadrupole mass spectrometer equipped with a triple-axis detector was also employed to enhance the instrument detection limit. With this technique, a complete separation for the analytes in water can be conducted in less than 10 min using a three-port SilFlow planar microfluidic device for back-flushing. Repeatability of retention times for all compounds were found to be less than 0.04% ( n = 10). The compounds cited can be analyzed from 1 ng/mL to 10 μg/mL, with a detection limit and correlation coefficient of at least 0.5 ng/mL and 0.999, respectively. A relative precision of less than 1.2% relative standard deviation (RSD) ( n = 20) at the 50 ng/mL level, with analyte recovery of greater than 99% ( n = 3) from 10 ng/mL to 10 μg/mL, was obtained. [ABSTRACT FROM AUTHOR]

Anaerobic, fixed film, bioreactors bioaugmented with a dechlorinating microbial consortium were evaluated as a potential technology for cost effective, sustainable, and reliable treatment of mixed chlorinated ethanes and ethenes in groundwater from a large groundwater recovery system. Bench- and pilot-scale testing at about 3 and 13,500 L, respectively, demonstrated that total chlorinated solvent removal to less than the permitted discharge limit of 100 μg/L. Various planned and unexpected upsets, interruptions, and changes demonstrated the robustness and reliability of the bioreactor system, which handled the operational variations with no observable change in performance. Key operating parameters included an adequately long hydraulic retention time for the surface area, a constant supply of electron donor, pH control with a buffer to minimize pH variance, an oxidation reduction potential of approximately −200 millivolts or lower, and a well-adapted biomass capable of degrading the full suite of chlorinated solvents in the groundwater. Results indicated that the current discharge criteria can be met using a bioreactor technology that is less complex and has less downtime than the sorption based technology currently being used to treat the groundwater. [ABSTRACT FROM AUTHOR]

A procedure was developed for oxidation of 4′,4″-bis(2-carboxybenzoyl)diphenyl sulfide with per acids (peracetic and trifluoroperacetic). The 4′,4″-bis(2-carboxybenzoyl)diphenyl sulfone obtained was converted into pseudodichloride, and three new polyarylenephthalides with regular alternation of the electron-acceptor (diphenyl sulfone) and electron-donor (diphenyl oxide, diphenyl sulfide, terphenyl) fragments were synthesized on its basis. The synthesized monomers can be used in the synthesis of new polyarylenephthalides exhibiting the electronic switching effect. [ABSTRACT FROM AUTHOR]

A low‐cost, chlorinated hydrocarbon solvent, 1,1,2,2‐tetrachloroethane (TeCA), is used as an effective additive for the triarylamine‐based organic hole‐transport material, Spiro‐OMeTAD, which is successfully applied in highly efficient solid‐state dye‐sensitized solar cells. A record power conversion efficiency of 7.7% is obtained by using the donor (D)‐π‐acceptor (A)‐dye, LEG4, in combination with the new method of TeCA‐doping of the hole‐transporting material Spiro‐OMeTAD. [ABSTRACT FROM AUTHOR]

Changes in composition of phytoplankton assemblages due to short-chained chlorinated hydrocarbons (tetrachloroethane, tetrachloroethylene and trichloroethylene) were studied in microcosm experiments with different initial diversities. Diversity decreased further during treatments in the less diverse 2011 summer assemblages, dominated by the euglenid Trachelomonas volvocinopsis (its relative abundance was nearly 70 %). Diversity did not change significantly during treatments in the more diverse 2012 summer assemblages, dominated by cryptomonads (their relative abundance was 40 %). The dominant Trachelomonas volvocinopsis in 2011, due to its insensitivity to the treatment and presumably high competition skills, filled released habitats occurring when sensitive species were not detectable any more. In contrast, cryptomonads were extremely sensitive to the treatments, their abundance decreased under detection limit in the treated assemblages, regardless of diversity conditions. Our results showed that population dynamics of dominant species determine the response to the contamination of the entire community, if these species display high resistance or resilience. If the dominant species was highly sensitive and recovered slowly, compensatory growth of rare species maintained high levels of ecosystem performance. [ABSTRACT FROM AUTHOR]

The hydrogen abstraction reactions by OH radicals from CHCl2CHCl2(R1), CH2ClCCl3(R2) and C2HCl5(R3) are investigated theoretically by semi-classical transition state theory. Many high-level density functional,ab initioand combinatory electronic structure calculation methods are used to evaluate the energies and ro-vibrational properties of the stationary points for the title reactions.xijvibrational anharmonicity coefficients, needed for semi-classical transition state theory, are calculated at the KMLYP/cc-pVTZ level of theory. Thermal rate coefficients are computed over the temperature range from 200 to 2000 K and compared with available experimental data. The computed rate constants for the reactions R1, R2 and R3 are fitted to the equationk(T) =ATnexp [ −E(T+T0)/(T2+T20)]. [ABSTRACT FROM PUBLISHER]

Carbonaceous materials such as activated carbon (AC) are effective adsorbents for a number of organic contaminants, and are often used in soil and sediment remediation to sequester organic contaminants. However, little is known about the abiotic reactivity (and thus, the long-term fate) of the carbonaceous material-bound contaminants. We studied the base-promoted dehydrochlorination kinetics of low-level (~1.25mg/g) 1,1,2,2-tetrachloroethane (TeCA) adsorbed to 17 different ACs varying in origin and physicochemical properties. Activated carbon-bound TeCA exhibited significant reactivity--at a given pH the apparent reaction kinetic constants of AC-bound TeCA are 13-70% of the respective kinetic constants of dissolved TeCA. Binding to ACs likely have affected the reactivity of TeCA via two important mechanisms. First, the deprotonated surface O-functional groups (e.g., carboxyl and phenolic groups) catalyzed the base-promoted dehydrochlorination reaction by serving as the conjugate bases. Second, at low contaminant loadings TeCA molecules likely resided primarily in the micropores of ACs (particularly, micropores with diameters of 0.67-1.6nm), wherein mass transfer of OH- (the nucleophile that reacts with TeCA) was inhibited. An important environmental implication is that carbonaceous materials not only sequester contaminants, but also allow contaminants to be slowly degraded in situ. [ABSTRACT FROM AUTHOR]

The study has focused on polyvinylcarbazole (PVK) composites with graphene. It has been shown that there is a noticeable nonadditive shoulder on the long-wavelength edge of the optical absorption of PVK in these samples, which can be attributed to the formation of a charge-transfer complex between PVK as a donor and graphene as an acceptor. The formation of the complex causes a significant nonlinear optical effect in the PVK/graphene composite. The revealed increase in both the nonlinearity coefficient with increasing laser intensity and the cross section with increasing incident energy density is due to the formation of the graphene radical anion, an additional species contributing to nonlinear absorption, with an increase in the radiation energy density. Nonlinear optical properties of PVK composites with graphene isolated from a solution in tetrachloroethane after 1.5-h centrifugation (sample 1) have been considered. It has been suggested that a significant decrease in optical transmission of laser radiation by the composite T = 0.4 at an energy density at focus of 502 J/cm is due to the formation of the PVK/graphene charge-transfer complex responsible for the nonadditive shoulder on the long-wavelength optical absorption edge of PVK. During photoexcitation of graphene in the PVK/graphene composites at a laser wavelength of 1064 nm, mobile holes are generated in PVK, indicating the formation of graphene radical anions as a result of charge transfer from PVK to photoexcited graphene. The observed increase in both β with an increase in the laser radiation intensity and the cross section (σ - σ) with an increase in the incident energy density may be due to either the contribution of nonlinear transitions ( S → S, S → S → S, T → T) or the formation of the additional species, the graphene-· radical anions, participating in nonlinear absorption by increasing the energy density at the focus ( F, J/cm). [ABSTRACT FROM AUTHOR]

Reaction of the rigid ligand 2,4,5,6-tetrachloro-1,3-benzenedicarboxylic acid (1,3-H2BDC-Cl4) with copper(II) nitrate in different solvent systems afforded two new complexes {[Cu(1,3-BDC-Cl4)(DMF)] (H2O)} n ( 1) and {[Cu(1,3-BDC-Cl4)(H2O)3] (dioxane) ·(H2O)} n ( 2), which were fully characterized by elemental analysis, IR spectroscopy, as well as single crystal and powder X-ray diffiraction techniques. Single-crystal X-ray diffraction reveals that complexes 1 and 2 crystallize in different space groups P21/ m and Pbca, respectivly. Compound 1 shows a two-dimensional (2D) (4,6)-connected layered network constructed by the connectivity between one-dimensional (1D) [-Cu-DMF-COO-] n chains and tetrachlorinated backbones of 1,3-BDC-Cl4, which is further assembled to generate a three-dimensional (3D) supramolecular framework through intermolecular O-H ···O and O-H ···Cl hydrogen-bonding interactions. Compound 2 features a 2D 4-connected sql coordination net formed by 1D [Cu-H2O] n chains and 1,3-BDC-Cl4 spacers, which is further extended into a 3D supramolecular network by multiple O-H ···O hydrogen-bonding interactions. The different structural features of the two compounds suggest that the choice of solvent systems should play a key role in the process of assembly. Their thermal and fluorescence properties were also investigated. [ABSTRACT FROM AUTHOR]

Trichloroethene (TCE) and tetrachloroethene (PCE) are chemical compounds which pose a serious threat for human health. Their specific properties make it possible that these substances may linger in soil and water for many years. These are the reasons why wells with water designed for drinking purposes have been subject of monitoring since 2006. This paper presents the results of monitoring research conducted in the soil-water environment within the framework in third phase of an ecological audit of land. The ecological audit of land made it possible to identify the cause and degree of the degradation, and helped formulate rationale for remedy decisions pertaining to the land (remediation/reclamation). The objective of the paper was to determine the pollution status of the soil-water environment and, subsequently, monitor (in years 2008-2010) the contents of the hazardous substances, namely trichloroethene and tetrachloroethene, within the area of the potential impact of metallurgical plant located in borders of the Main Underground Water Reservoir Wierzbica-Ostrowiec (GZWP 420) in in voivodeship Świętokrzyskie. [ABSTRACT FROM AUTHOR]

A procedure for the design of an aerobic cometabolic process for the on-site degradation of chlorinated solvents in a packed bed reactor was developed using groundwater from an aquifer contaminated by trichloroethylene (TCE) and 1,1,2,2-tetrachloroethane (TeCA). The work led to the selection of butane among five tested growth substrates, and to the development and characterization from the site's indigenous biomass of a suspended-cell consortium capable to degrade TCE (first order constant: 96 L g day at 30 °C and 4.3 L g day at 15 °C) with a 90 % mineralization of the organic chlorine. The consortium immobilization had strong effects on the butane and TCE degradation rates. The microbial community structure was slightly changed by a temperature shift from 30 to 15 °C, but remarkably affected by biomass adhesion. Given the higher TCE normalized degradation rate (0.59 day at 15 °C) and attached biomass concentration (0.13 g L at 15 °C) attained, the porous ceramic carrier Biomax was selected as the best option for the packed bed reactor process. The low TeCA degradation rate exhibited by the developed consortium suggested the inclusion of a chemical pre-treatment based on the TeCA to TCE conversion via β-elimination, a very fast reaction at alkaline pH. To the best of the authors' knowledge, this represents the first attempt to develop a procedure for the development of a packed bed reactor process for the aerobic cometabolism of chlorinated solvents. [ABSTRACT FROM AUTHOR]

The environmental implications of carbon nanomaterials have received much attention. Nonetheless, little is known about how carbon nanomaterials might affect the abiotic transformation of organic contaminants in aquatic environments. In this study, we observed that three functionalized multiwalled carbon nanotubes (MWCNTs)-including a hydroxylated MWCNT (OH-MWCNT), a carboxylated MWCNT (COOH-MWCNT), and an aminated MWCNT (NH2MWCNT)-all had strong catalytic effects on the dehydrochlorination of 1,1,2,2-tetrachloroethane (TeCA) at three different pH (7, 8, and 9); notably, the most significant effects (up to 130% increase in reaction rate) were observed at pH 7, at which reaction kinetics was very slow in the absence of MWCNT. The primary mechanism was that the -NH2 group and the deprotonated -COOH and -OH groups serve as bases to catalyze the reaction. Modeling results indicate that at any given pH the transformation kinetic constants of MWCNT-adsorbed TeCA were up to 2 orders of magnitude greater than the respective kinetic constant of dissolved TeCA. The overall catalytic effects of the MWCNTs depended both on the basicity of the surface functionalities of MWCNT and on the adsorption affinities of MWCNT for TeCA. Interestingly, Suwannee River humic add-selected as a model dissolved organic matter-had negligible effects on the dehydrochlorination kinetics, even though it is rich in surface O-functionalities. An important environmental implication is that carbon nanotubes released into the environment might significantly affect the fate of chlorinated solvents. [ABSTRACT FROM AUTHOR]

Intramolecular and intermolecular alkylations of carbocation precursors of limited ionization ability, principally N,O-acetals, without the use of an exogenous reagent have been developed. The reactions are carried out in 1,1,2,2-tetrachloroethane (TCE) and take advantage of the ability of this solvent to continuously release small amounts of HCl by thermolytic elimination. A study of the reaction led to several improved protocols such as (1) preheated TCE, (2) microwave-assisted reactions, and (3) flow or sealed-tube conditions, which allow significant reaction rate enhancements and made possible some challenging reactions such as the α-amidoalkylation of ketones. Studies using flow chemistry confirmed not only that very low concentrations of HCl generated from the solvent were responsible for the reactivity but also that TCE had additional beneficial properties in comparison to other chlorinated solvents such as dichloroethane. The method can easily be extended to the alkylation using proelectrophiles such as π-activated alcohols, which are normally unreactive toward HCl catalysis. This work represents the first successful use of HCl, the simplest strong Brønsted acid, as an efficient alkylation catalyst. [ABSTRACT FROM AUTHOR]

The nonlinear optical properties of solutions of (2,3,9,10,16,17,23,24-tetra-15-crown-5-phthalocyaninato)indium(III) [(15C5)Pc]In(OH) in tetrachloroethane (TCE) have been studied by the z-scan method. It has been found that a nonlinear optical response is due to supramolecular associates formed in a tetrachloroethane solution by heating to 90°C/slow cooling to room temperature cycling. The formation of the supramolecular associates has been studied by atomic force microscopy (AFM) and electronic absorption spectroscopy (EAS). It has been shown that a single thermal treatment of [(15C5)Pc]In(OH) solutions in TCE results in the predominant formation of dimers, as evidenced by both a short-wavelength shift of the Q-absorption band of the monomeric complex (λ = 692 nm) to the band of λ = 653 nm and height doubling of molecular entities as measured by AFM. The dimers are responsible for the two-photon absorption measured in the femtosecond range, which has a relatively high cross section of σ = 1.38 × 10 cm s/(molecule, photon) or 1.38 × 10 GM. According to the AFM data, three cycles of heat treatment of the solution leads to the formation of supramolecular assemblies of about 200 nm length. The optical spectrum exhibits long-wavelength absorption at λ = 841 nm and the long-wavelength edge near 1300 nm. In the case of nanosecond 1064-nm laser irradiation, the linear absorption S → S is primary, having the cross section of σ = α/ N = 2.3 × 10 cm. The known high quantum yield (close to unity) of triplet states of indium phthalocyanines suggests that the main nonlinear optical effect is determined by intersystem crossing S → T and triplet-triplet absorption T → T. The absorption cross section is σ = 1.14 × 10 cm. [ABSTRACT FROM AUTHOR]

Mesoporous hybrid silica-organic materials containing homogeneously distributed stable mono- or dinitroxide radicals covalently bound to the silica surface were developed as polarization matrixes for solid-state dynamic nuclear polarization (DNP) NMR experiments. For TEMPOcontaining materials impregnated with water or 1,1,2,2- tetrachloroethane, enhancement factors of up to 36 were obtained at ~100 K and 9.4 T without the need for a glassforming additive. We show that the homogeneous radical distribution and the subtle balance between the concentration of radical in the material and the fraction of radicals at a sufficient inter-radical distance to promote the cross-effect are the main determinants for the DNP enhancements we obtain. The material, as well as an analogue containing the poorly soluble biradical bTUrea, is used as a polarizing matrix for DNP NMR experiments of solutions containing alanine and pyruvic acid. The analyte is separated from the polarization matrix by simple filtration. [ABSTRACT FROM AUTHOR]

Abstract: In the presence of FeCl3, C60 in 1,1,2,2-tetrachloroethane reacted at 150°C to produce a dumbbell-shaped dimer C120. We propose a reaction mechanism that includes FeCl3-mediated generation of an intermediate C60 radical cation, which reacts with C60 to form the dimer. The respectable chemical yield (21%) and quantity (106mg) of the product will open new possibilities for investigating solution-phase polymerization of fullerenes as well as for conducting applied research on C120. [Copyright &y& Elsevier]

1. Iodogen (tetrachloro-diphenyl glycoluril) dissolved in DMSO (dimethyl sulphoxide) appears indispensable in radioiodination of hypericin for a new anticancer strategy. We studied the safety of intravenously administered iodogen/DMSO in mice ( n = 132). 2. Median lethal dose (LD50) of iodogen/DMSO was determined with doses of 40.0, 50.0, 55.0, 60.0, 65.0 and 70.0 mg/kg. Next, toxicity of iodogen/DMSO at 30.0 mg/kg was evaluated using saline and DMSO as controls. Changes in behaviour, body weight and serum biochemistry were evaluated. Histopathology of lungs, heart, liver and kidney was performed. 3. LD50 values of iodogen/DMSO were 59.5 mg/kg (95% confidence limits (CI): 54.1-65.4 mg/kg) and 61.0 mg/kg (95%CI: 56.2-66.2 mg/kg) for female and male mice, respectively. Similar to that of control groups, no animal deaths were encountered after iodogen/DMSO administration at 30.0 mg/kg. Body weights over 24 h were not altered in all groups, but significantly higher in iodogen/DMSO and DMSO groups ( p < 0.05) 14 d post-injection. Blood urea nitrogen and alkaline phosphatase increased ( p < 0.05) in iodogen/DMSO group without clinical symptoms. No pathologies were found by gross and microscopic inspection. 4. A single dose of iodogen/DMSO up to 30.0 mg/kg, over 3000 times the dose in potential human applications, appears safe, with an LD50 doubling that dose in mice. [ABSTRACT FROM AUTHOR]

Palladized nanoscale zerovalent iron (Pd/NZVI) has been utilized for source zone control, yet the reductant responsible for pollutant transformation and the optimal conditions for subsurface application remain poorly understood. Here, trends in Pd/Fe reactivity toward 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA) and cis-dichloroethene (cis-DCE) were compared in H2O and D2O batch systems as a function of pH, chlorinated solvent concentration, Pd surface loading, Pd/Fe mass loading, Pd/Fe aging time, and zerovalent iron [Fe(0)] particle size. For Pd/NZVI, the solvent kinetic isotope effect [i.e., kobs(H2O)/kobs(D2O) or SKIE] for 1,1,1,2-TeCA and cis-DCE reduction increased substantially with Pd loading and Pd/NZVI concentration, evidence that multiple pathways exist for chlorinated solvent reduction. At low Pd loadings and Pd/NZVI concentrations with relatively small SKIEs (less than 5), we propose that modest reactivity enhancements (≤10-fold) reflect more efficient electron transfer to 1,1,1,2-TeCA from Fe(0) facilitated by Pd nanodeposits. Much larger SKIEs (e.g., exceeding 100 for cis-DCE) imply the involvement of atomic hydrogen in more reactive systems with high Pd loadings and Pd/NZVI concentrations. Generally, evidence of SKIEs supporting a dominant role for atomic hydrogen was not observed for Pd/Fe prepared from micrometer-sized Fe(0), or for any size of nonpalladized Fe(0). During anaerobic aging of Pd/NZVI, decreases in the SKIE for 1,1,1,2-TeCA reduction suggest that atomic hydrogen will contribute to reactivity for only approximately 1 week after application. [ABSTRACT FROM AUTHOR]

In part one of this work, it was shown that in addition to sodium formate, hexachloroethane (HCE) and perchloroethylene are the main products of the catalytic hydrodechlorination of CCl in a medium of sodium hydroxide solutions. These products undergo mutual transformations under the conditions of the process. Since the industrial requirements for perchloroethylene considerably exceed those for HCE, the regularities of the catalytic hydrodechlorination of HCE, pentachloroethane, 1,1,2,2-tetrachloroethane, 1,1,2-trichloroethane, and 1,2-dichloroethane are studied in part two, using 1.5 wt % Pd on sibunit as the catalyst. It is found the fraction of hydrogen substited for chlorine grows and the reactivity of the products diminishes with a reduction in the number of chlorine atoms in a polychloroethane molecule. Ethane and ethylene are the final reaction products after a rather long contact time. The kinetics of HCE catalytic hydrodechlorination is studied n the temperature range of 353-393 K and at hydrogen partial pressures of 50-810 kPa. It is shown that the only reaction product is perchloroethylene; i.e., the transformation of HCE proceeds via the elimination of two chlorine atoms, while the limiting stage of the process is product dissolution in the aqueous-alkaline reaction mass. The form of the kinetic equation is found to be w = 2.1 × 10 × exp[−(16200 ± 400)/ RT] C C $P_{H_2 }^{0.5} $ mol/(L s). The possibility of using the catalytic hydrodechlorination of chlorohydrocarbons in a medium of sodium hydroxide solutions for the recycling of chloroorganic wastes containing CCl and polychloroethanes is demonstrated. [ABSTRACT FROM AUTHOR]

Two types of bis(ß-diketonato) Co(II) complexes, [Co(CNacac)2] (CNacac = 3-cyano-pentane- 2,4-dionato), and [Co(dbm)2] (dbm = dibenzoylmethanato or l,3-diphenyl-propane-l,3-dionato) were examined as linear building blocks for the construction of coordination polymers in combination with two oligopyridines, 1,4-bis(4,2':6',4"-terpyridin-4'-yl)benzene (LI) and l,3-bis(3,2':6',3"- terpyridin-4'-yl)benzene) (L2). From combinations of [Co(CNacac)2] with LI and L2, 2-D coordination polymers, [Co(CNacac)2]2(Lt)(CHCl3)(CH3OH) (CoCN-1) and [Co(CNacac)2](L2),/ 2 (tetrachloroethane)3/2 (CoCN-2), are obtained. Both CoCN-1 and CoCN-2 have 2D (4,4) net structures, in which LI and L2 are tetradentate. In contrast, combination of [Co(dbm)2] with L2 affords a l-D coordination polymer, [Co(dbm)2](L2)-4(CH3OH) (Codbm-1), in which L2 is bidentate. L2 as a tetradentate ligand was inhibited by bulky phenyl rings in [Co(dbm)2], These results indicate that [Co(CNacac)2] with a relatively simplified structure is useful as a linear building block in combinations with bulky oligopyridines. [ABSTRACT FROM AUTHOR]

A polymer incorporated with a pyrenylcarbazole pendant poly(12-(3-(pyren-1-yl)-carbazol-9-yl)dodecyl methacrylate, denoted as PCP) was synthesized and applied in the functionalization of multi-walled carbon nanotubes (MWCNTs) by noncovalent π–π interaction. The PCP–MWCNT hybrids were isolated and characterized by SEM, TEM, and UV-visible absorption and emission spectroscopies. The strong interaction between PCP and the MWCNT in a 1,1,2,2-tetrachloroethane (TCE) solution was studied. It demonstrated an effective quenching effect on emission from PCP by the MWCNTs. DFT calculations showed electron delocalization between the pyrene and carbazole moieties. The LUMO of PCP is mainly located on the pyrene moiety while the LUMO + 1 is predominantly positioned on the carbazole moiety. Femtosecond transient absorption (TA) experiments determined the characteristic TA peaks of the excited states, which have contributions from both the pyrene and carbazole moieties. The excited state lifetime of the polymer PCP was measured to be 659 ps and the photo-excited electrons were injected into the MWCNTs very effectively on a time scale of 420 fs. [ABSTRACT FROM AUTHOR]

Halogenoethane derivatives are known to exhibit different polymorphs involving a different translational, orientational, and conformational order. The 1,1,2,2-tetrachloroethane (Cl2HC–CHCl2) exhibits a normal pressure orthorhombic phase β (space group P212121 with Z = 8 and Z′ = 2), formed by molecules with one of the two gauche conformations. At high pressure, the stable polymorph is known to be monoclinic (space group P21/c, with Z = 2 and Z′ = 0.5), phase α, in which only the trans conformer appears. In this work, we demonstrate the existence of a normal pressure metastable polymorph, phase γ, for which the two gauche conformers show up in the asymmetric unit of a monoclinic (space group P21/c with Z = 8 and Z′ = 2) structure. The new phase γ is obtained by recrystallization upon heating the glass obtained after quench of the melt. It displays shorter type II Cl···Cl contacts than the high-pressure phase α due to attractive and directional interactions. Halogenoethane derivatives are known to exhibit different polymorphs involving a different translational, orientational, and conformational order. The 1,1,2,2-tetrachloroethane (Cl2HC−CHCl2) exhibits a normal pressure orthorhombic phase β (space group P212121 with Z = 8 and Z′ = 2), formed by molecules with one of the two gauche conformations. At high pressure, the stable polymorph is known to be monoclinic (space group P21/c, with Z = 2 and Z′ = 0.5), phase α, in which only the trans conformer appears. In this work, we demonstrate the existence of a normal pressure metastable polymorph, phase γ, for which the two gauche conformers show up in the asymmetric unit of a monoclinic (space group P21/c with Z = 8 and Z′ = 2) structure. The new phase γ is obtained by recrystallization upon heating the glass obtained after quench of the melt. It displays shorter type II Cl···Cl contacts than the high-pressure phase α due to attractive and directional interactions. [ABSTRACT FROM AUTHOR]

The association constants for a family of 96 closely related zinc porphyrin--pyridine ligand complexes have been measured in two different solvents, toluene and 1,1,2,2-tetrachloro-ethane (TCE). The zinc porphyrin receptors are equipped with phenol side arms, which can form intramolecular H-bonds with ester or amide side arms on the pyridine ligands. These association constants were used to construct 64 chemical double mutant cycles, which measure the free energy contributions of intramolecular H-bonding interactions to the overall stability of the complexes. Measurement of association constants for the corresponding intermolecular H-bonding interactions allowed determination of the effective molarities (EM) for the intramolecular interactions. Comparison of ligands that feature amide H-bond acceptors and ester H-bonds at identical sites on die ligand framework show that the values of EM are practically identical. Similarly, the values of EM are practically identical in toluene and in TCE. However, comparison of two ligand series that differ by one degree of torsional freedom shows that the values of EM for die flexible ligands are an order of magnitude lower than for the corresponding rigid ligands. This observation holds for a range of different supramolecular architectures with different degrees of receptor--ligand complementarity and suggests that in general the cost of freezing a rotor in supramolecular complexes is of the order of 5 kj/mol. [ABSTRACT FROM AUTHOR]

The toxicity of three highly volatile organic solvents - tetrachloroethane (Cl2HC-CHCl2), tetrachloroethylene (Cl2C=CCl2), trichloroethylene (ClHC=CCl2) - was studied on Unio crassus specimens. The tested chlorinated hydrocarbons sink to the bottom of standing water bodies due to their high density; therefore they represent an increased risk for benthic organisms. For a start, all three compounds were applied in 100% saturation. In the case of tetrachloroethylene and trichloroethylene all specimens died within a few days. In the case of tetrachloroethane the intoxication process was much faster, all the specimens died within 4 hours. Tetrachloroethane proved to be the most toxic compound; its diluted solutions were further tested: in the 5% solution all U. crassus specimens died after 24 hours. The 1% solution had a strong disturbing effect on the behaviour of the bivalves, which was gradually moderated and eventually stopped on the 33rd day. These results suggest that the examined chlorinated hydrocarbons are strongly toxic to living organisms even in aquatic medium and cause rapid death even in low concentrations. [ABSTRACT FROM AUTHOR]

An intramolecular Pauson-Khand type cycloaddition reaction of ene-vinylidenecyclopropanes with carbon monoxide has been established by using [Rh(COD)Cl]2as the catalyst. The reaction was found to be highly efficient in solvents of 1,2-dichloroethane and 1,1,2,2-tetrachloroethane to give excellent yields of 90–99%. The reaction provides easy access to a series of fused 6,5-ring structures containing spiro-cyclopropane units that are useful for drug design and development. A mechanism of this cycloaddition process has been proposed accounting for structures of resulting products that were unambiguously assigned by X-ray diffractional analysis. [ABSTRACT FROM AUTHOR]

Nanoscale zerovalent iron (NZVI) was aged over 30 days in suspension (2 g/L) with different anions (chloride, perchlorate, sulfate, carbonate, nitrate), anion concentrations (5, 25, 100 mN), and pH (7, 8). During aging, suspension samples were reacted periodically with 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA) and Cr(VI) to determine the time scales and primary mode of NZVI reactivity loss. Rate constants for 1,1,1,2-TeCA reduction in Cl-, SO42-, and ClO4- suspensions decreased by 95% over 1 month but were generally equivalent to one another, invariant of concentration and independent of pH. In contrast, longevity toward 1,1,1,2-TeCA depended upon NO3- and HCO3- concentration, with complete reactivity loss over 1 and 14 days, respectively, in 25 mN suspensions. X-ray diffraction suggests that reactivity loss toward 1,1,1,2-TeCA in most systems results from Fe(0) conversion into magnetite, whereas iron carbonate hydroxide formation limits reactivity in HCO3- suspensions. Markedly different trends in Cr(VI) removal capacity (mg Cr/g NZVI) were observed during aging, typically exhibiting greater longevity and a pronounced pH-dependence. Notably, a strong linear correlation exists between Cr(VI) removal capacities and rates of Fe(II) production measured in the absence of Cr(VI). While Fe(0) availability dictates longevity toward 1,1,1,2-TeCA, this correlation suggests surface-associated Fe(II) species are primarily responsible for Cr(VI) reduction. [ABSTRACT FROM AUTHOR]

The WBC-2 consortium is an organohalide-respiring anaerobic microbial enrichment culture capable of dechlorinating 1,1,2,2-tetrachloroethane (TeCA) to ethene. In the WBC-2 culture, TeCA is first transformed to íraMS-dichloroethene (tDCE) by dichlo-roelimination; tDCE is subsequently transformed to vinyl chloride (VC) and then to ethene by hydrogenolysis. Analysis of 16S rRNA gene clone libraries from culture DNA revealed sequences from three putative dechlorinating organisms belonging to De-halococcoides, Dehalobacter, and Dehalogenimonas genera. Quantitative PCR primers were designed for each of these sequences, and their abundance was quantified in enrichment cultures over time. These data revealed that complete dechlorination of TeCA to ethene involves all three organisms. Dehalobacter spp. grew during the dihaloelimination of TeCA to tDCE, while Dehalococ-coides and Dehalogenimonas spp. grew during hydrogenolysis of tDCE to ethene. This is the first time a genus other than Dehalo-coccoides has been implicated in dechlorination of tDCE to VC. [ABSTRACT FROM AUTHOR]

ZVI-Clay is an emerging remediation approach that combines zero-valent iron (ZVI)-mediated degradation and in situ stabilization of chlorinated solvents. Through use of in situ soil mixing to deliver reagents, reagent-contaminant contact issues associated with natural subsurface heterogeneity are overcome. This article describes implementation, treatment performance, and reaction kinetics during the first year after application of the ZVI-Clay remediation approach at Marine Corps Base Camp Lejeune, North Carolina. Primary contaminants included trichloroethylene, 1,1,2,2-tetrachloroethane, and related natural degradation products. For the field application, 22,900 m3 of soils were treated to an average depth of 7.6 m with 2% ZVI and 3% sodium bentonite (dry weight basis). Performance monitoring included analysis of soil and water samples. After 1 year, total concentrations of chlorinated volatile organic compounds (CVOCs) in soil samples were decreased by site-wide average and median values of 97% and >99%, respectively. Total CVOC concentrations in groundwater were reduced by average and median values of 81% and >99%, respectively. In several of the soil and groundwater monitoring locations, reductions in total CVOC concentrations of greater than 99.9% were apparent. Further reduction in concentrations of chlorinated solvents is expected with time. Pre- and post-mixing average hydraulic conductivity values were 1.7 × 10−5 and 5.2 × 10−8 m/s, respectively, indicating a reduction of about 2.5 orders of magnitude. By achieving simultaneous contaminant mass depletion and hydraulic conductivity reduction, contaminant flux reductions of several orders of magnitude are predicted. [ABSTRACT FROM AUTHOR]

Cellulose tridecanoates of various molecular weights were synthesized, and their characteristics in chloroform and tetrachloroethane solutions were studied by methods of translational diffusion, velocity sedimentation, flow birefringence (Maxwell's method), and viscometry. The effects of solvent and temperature on the conformational characteristics of the macromolecules under consideration were examined. The anisotropy of the monomeric unit of cellulose tridecanoates was studied, and the contribution of pendant chains to the optical anisotropy of macromolecules of cellulose esters with aliphatic substituents was analyzed. [ABSTRACT FROM AUTHOR]

Abstract: The treatment of aqueous solutions of 1,1,2,2-tetrachloroethane was performed by anodic oxidation at boron doped diamond (BDD), cathodic reduction at silver and coupled processes. Experiments were performed in macro and micro reactors with an interelectrode distance lower than 100μm. Drastically higher abatements of the chlorinated compound and current efficiencies were obtained in microdevices that, furthermore, allowed to perform the electrolyses with low cell voltages in the absence of supporting electrolyte. When reduction and oxidation processes were carried out simultaneously in the microreactor, a higher abatement of pollutants was obtained with the same amount of the passed charge and applied cell voltage with respect to uncoupled processes. The effect of some operative parameters, including the flow rate, the current density, the initial concentration of the pollutant and the interelectrodic distance, on the performances of the process was also studied. [Copyright &y& Elsevier]

The effect of two carbon sources namely sodium acetate and ethanol was studied in bench-scale Upflow Anaerobic Sludge Blanket (UASB) reactors for the removal of chlorinated ethanes i.e., 1,1,2-Trichloroethane (TCA) and 1,1,2,2-Tetrachloroethane (TeCA) contained in the simulated wastewaters. The Hydraulic Retention Time (HRT) was maintained as 24 hours in all the reactors. The granular biomass in the test reactors R2 and R3 were acclimated to 40 mg/L of TCA and 20 mg/L of TeCA, respectively. The effluent TCA and TeCA concentrations were 0.03 mg/L and 0.18 mg/L, respectively, at the end of acclimation phase. Sodium acetate and ethanol both were found to be suitable as the primary substrates in the biodegradation of TCA and TeCA. However, lower concentrations of the toxic pollutants (TCA and TeCA) were obtained in the effluents with the use of sodium acetate. The COD removal efficiency in the test reactors (R2 and R3) varied in the range of 95 % to 98.2 % accompanied by the formation of 1,2-Dichloroethane (DCA) as the major intermediate. [ABSTRACT FROM AUTHOR]