Search

International audience

The financial support of this work was undertaken by the Ministry of Economy,Industry and Competitiveness of the Spanish Government (CTQ2016-79646-P,someco-founded with ERDF funds),and the Basque Government(Project IT912-16). Jose Valecillos is thankful for his fellowship by the Ministry of Economy,Industry and Competitiveness of the Spanish Government(BES2014069980). The authors are thankful for technical and human support provided by IZO-SGI SGIker of UPV/EHU European funding(ERDFandESF).

Over the last two decades, metal–organic frameworks (MOFs) have received particular attention because of their attractive properties such as permanent nanoporosity and the extraordinary functionality of open coordination sites (OCSs) at metal nodes. In particular, MOFs with open-state OCSs have shown potential in applications such as chemical separation, molecular sorption, catalysis, ionic conduction, and sensing. Thus, the activation of OCSs, i.e., the removal of coordinated solvent to produce open-state OCSs, has been viewed as an essential step that must be performed prior to the use of the MOFs in the aforementioned applications. This Feature Article focuses on the chemical functions of the commonly unreactive chloromethanes, i.e., dichloromethane (DCM) and trichloromethane (TCM), including their coordination to OCSs and activation of OCSs. Treatment with a chloromethane is a chemical route to activate OCSs that does not require an additional supply of external thermal energy. Importantly, a plausible mechanism for the chemical process, in which DCM and TCM weakly coordinate to the OCSs and then spontaneously dissociate in an intermediate step, which is proposed based on the results obtained from Raman studies will be discussed. Possible applications of chloromethane treatment to activate large-area MOF films and MOF–polymer mixed matrices, which can be propagated in molecular capture, will also be described.

This paper presents the first empirical experimental data on the skin absorption of methyl chloride gas using an in vitro technique and human skin. Methyl chloride is a commonly used industrial agent that is known to be an inhalational hazard but is also reported to be absorbed through human skin in amounts that contribute substantially to systemic intoxication. As a result is has been assigned a skin notation by the ACGIH. Other than predictive models, there is a general paucity of experimental data on the skin absorption of methyl chloride and therefore a distinct lack of empirical evidence in the open literature to support the assignment of a skin notation for this chemical. This study found that methyl chloride permeates through human epidermis when exposed at high atmospheric concentrations within relatively short timeframes. Therefore, providing important initial empirical evidence in support of the assignment of a skin notation.

Reactions between Al containing materials and counterfeit refrigerant chloromethane (R-40) were investigated under various conditions. The addition of Mg effected a reaction indicating that trimethylaluminum may have been produced in the reaction. A different study involving Al-foil, AlCl3 and chloromethane resulted in cracks detected on the Al-foil which reduced in weight by 19% and methane was detected. Studies conducted either at room temperature or at 80°C with two other genuine refrigerants, R-142b (1-chloro-1,1-difluoroethane) and R-133a (2-chloro-1,1,1-trifluoroethane) did not form organoaluminum compounds. Several commercially available refrigerant oils were subjected to Me3Al. Only polyester oil resulted in a decrease in the quantity of methane released upon final deactivation with alcohol. Various chemicals were added to Me3Al in order to find which ones would react and not produce methane. Phthalaldehyde was determined to be the most efficient reagent by deactivating approximately 50% of the methyl groups on Me3Al.

Halogenated volatile organic compounds (VOCs) emitted by terrestrial ecosystems, such as chloromethane (CH3Cl), have pronounced effects on troposphere and stratosphere chemistry and climate. The magnitude of the global CH3Cl sink is uncertain since it involves a largely uncharacterized microbial sink. CH3Cl represents a growth substrate for some specialized methylotrophs, while methanol (CH3OH), formed in much larger amounts in terrestrial environments, may be more widely used by such microorganisms. Direct measurements of CH3Cl degradation rates in two field campaigns and in microcosms allowed the identification of top soil horizons (i.e., organic plus mineral A horizon) as the major biotic sink in a deciduous forest. Metabolically active members of Alphaproteobacteria and Actinobacteria were identified by taxonomic and functional gene biomarkers following stable isotope labeling (SIP) of microcosms with CH3Cl and CH3OH, added alone or together as the [C-13]-isotopologue. Well-studied reference CH3Cl degraders, such as Methylobacterium extorquens CM4, were not involved in the sink activity of the studied soil. Nonetheless, only sequences of the cmuA chloromethane dehalogenase gene highly similar to those of known strains were detected, suggesting the relevance of horizontal gene transfer for CH3Cl degradation in forest soil. Further, CH3Cl consumption rate increased in the presence of CH3OH. Members of Alphaproteobacteria and Actinobacteria were also C-13-labeled upon [C-13]-CH3OH amendment. These findings suggest that key bacterial CH3Cl degraders in forest soil benefit from CH3OH as an alternative substrate. For soil CH3Cl-utilizing methylotrophs, utilization of several one-carbon compounds may represent a competitive advantage over heterotrophs that cannot utilize one-carbon compounds.

The catalytic hydrogenation of CO2 to CH3OH has a bright prospect along with high market demand. Methanol (CH3OH) was needed as raw material in the petrochemical industry to produce formaldehyde, chloromethane, amine acetate and also as an new alternative environmentally friendly energy. This study aims to obtain a Cu/Zn/Al2O3 catalyst design and the effect of feed temperature on CO2 conversion, CH3OH selectivity, and CH3OH yield. The preparation of Cu/Zn/Al2O3 catalysts by co-precipitation method resulted in the percentage ratio of Cu/Zn/Al metal composition of 66,7: 27,4: 4,29 and the catalyst surface area of 98,3411 m2/g. The H2:CO2 ratio in the feed gas is 3: 1. The fixed-bed reactor has the dimension of 1.5 cm in inner diameter, 5 cm in length of reactor bed, and is equipped by a furnace upstream the reactor bed. The reaction was carried out at the pressure of 30 bar and the flowrate is kept constant. The feed temperature varies at 220, 250, 280 °C. At the feed temperature of 250 °C, the best performance is obtained: the CO2 conversion of 21.8%, the CH3OH selectivity of 82.76%, and the CH3OH yield of 18.04%, which is reached after 240 minutes of the reaction (steady state).

The proximity of values of the electronic chemical potential µ of the [B6H6]2– and OH– anions allows us to assume the possibility of participation of [B6H6]2–, instead of OH–, in chemical reactions proceeding in a basic medium. A theoretical study of reactions of the [B6H6]2– anion with halogenoalkanes has been carried out with chloromethane and 2-chlorobutane as examples using the B3LYP/6-311G* approach. The interaction of [B6H6]2– with CH3Cl in a certain sense is similar to the reaction of formation of primary alcohols from primary halogenoalkanes under the influence of an alkali and results in substituted product [B6H6CH3]–, i. e. the protonated form of anion [B6H5CH3]2–. At the same time, interaction of [B6H6]2– with 2-chlorobutane has to proceed similar to the reactions of elimination of secondary and tertiary halogenoalkanes in an alkaline medium to form unsaturated compounds and according to the calculations has to result in 2-butene. Transition states (TSs) have been located and the energy profiles of reactions have been calculated. In the course of the interaction with CH3Cl, the exopolyhedral substitution in the [B6H6]2– anion can proceed practically without the activation barrier (h ~ 1.8 kcal/mol), whereas the elimination reaction of 2-chlorobutane under the influence of [B6H6]2– has to overcome an insignificant threshold of h ~ 4.2 kcal/mol.

The transformation of chloromethane into light olefins (C2–C4) has been studied both on HZSM-5 catalysts with different SiO2/Al2O3 ratios (30, 80, and 280) and on SAPO-n catalysts (SAPO-34 and SAPO-18) in order to analyze the role of shape selectivity and acidity in the kinetic behavior. The catalysts have been prepared by agglomerating these acid functions with bentonite and α-Al2O3, and the kinetic runs have been performed in a fixed bed reactor under the following operating conditions: 350 and 450 °C; space time, 2.35, 5.89, and 14.99 gcat h (molCH2)−1; and time on stream, 255 min. A comparison of the reaction indices (conversion of chloromethane, selectivity to light olefins, and propylene fraction) at zero time and throughout time on stream using the different catalysts has allowed establishing, on the one hand, the significance of the shape selectivity and acidity of these catalysts (which are more influential in this reaction than in the transformation of methanol), and on the other, the need for a...

Burning incense indoors is a common behavior in Southeast Asia. In this investigation, needle trap samplers (NTS), a novel, green analytical technology is used for sampling gaseous combustion by-products from sandalwood incense coils. To extract indoor volatile organic compounds (VOCs), two NTS are prepared, one using 60–80 mesh and the other using 100–120 mesh divinylbenzene (DVB) particles packed in 22-gauge stainless steel needles. This work compares extraction efficiency of an NTS and that of a commercially available 100 μm polydimethylsiloxane solid phase microextration (PDMS-SPME) fiber sampler. Experimental results indicated that the 100–120 mesh DVB-NTS performed best among all samplers during a 1 h sampling period. The main extracted compounds were toluene, ethylbenzene, propane, chloromethane, 1,3-butadiene, methanol and dichloromethane. The potential use of small badge-sized or pen-sized NTS for the indoor atmosphere and occupational hygiene applications is addressed.

Thermal decomposition of polyvinylchloride (PVC)–wood and wood component mixtures were examined under slow and fast heating by pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) and thermogravimetry/mass spectrometry(TG/MS) techniques in order to clarify the chemical interaction of biomass materials and PVC during thermal decomposition. A hardwood and a softwood (beech and pine), their lignin and two types of cellulose (Avicel and Whatman) were chosen as natural polymer components. Comparing the gaseous and liquid pyrolysis products of pure samples to those of mixtures it was found that considerably lower amount of several reactive compounds have been produced when the biomass sample was mixed with PVC. On the other hand significant amount of chloromethane appeared in the pyrolysate of wood and lignin samples mixed with PVC under fast and slow pyrolysis conditions as well, but only in traces of chlorinated organic compounds were detected from cellulose mixtures. It was concluded that the methoxy groups at phenolic rings in lignin are the methyl source of chloromethane formation, and this reaction consumed most of the HCl evolved from PVC.

The reactive fragment [Tp′Rh(PMe3)], generated from the thermal precursor Tp′Rh(PMe3)(Me)H, is found to cleave the C–Cl bonds of chlorohydrocarbons under mild conditions. Reaction with chloromethane gives clean formation of an initial C–H activation product, which rearranges to form the C–Cl activation product at 30 °C. Reaction with dichloromethane or benzyl chloride gives a mixture of C–Cl activation products as well as products from chlorination. Reaction with chlorocyclohexane gives a mixture of intermediates from C–H activation, which react further upon heating to give a C–Cl cleavage product as well as the β-chloride elimination product Tp′Rh(PMe3)(Cl)H plus cyclohexene. Complete conversion from a C–H activation product to a C–Cl activation product was observed in the reaction with 1,2-dichloroethylene, where β-elimination is circumvented. Activation of 1-chlorobutane, 1,2-dichloroethane, or 1,4-dichlorobutane gives a mixture of C–Cl activation products as well as Tp′Rh(PMe3)(Cl)H plus olefin. Simil...

A series of M/ZSM-5 (M = Co, Fe, Ce, and Mn) catalysts with different molar ratios of SiO2/Al2O3 (30, 107) was prepared via a traditional wetness impregnation, and further characterized by XRD, BET, H2-TPR, NH3-TPD, and XPS as well as activity test for the catalytic combustion of chloromethane. Characteristic structure of ZSM-5 is basically maintained even after impregnating the various metallic components. Catalytic activities achieving under an atmosphere of 1500 ppm CH3Cl, 10% O2, and GHSV of 15,000 h−1 of the investigated catalysts follow a trend of Co/ZSM-5-30, Ce/ZSM-5-30 > Co/ZSM-5-107, Ce/ZSM-5-107, Fe/ZSM-5-30, Mn/ZSM-5-30 > Mn/ZSM-5-107, Fe/ZSM-5-107 > H-ZSM-5-30 > H-ZSM-5-107. The binary Co/ZSM-5-30 and Ce/ZSM-5-30 show the satisfactory conversions of CH3Cl (87% and 95%) associated with a low yield of CO (9.6% and 16%) at 400 °C, owing to the excellent redox properties (determined by the chemical nature of the loaded metallic components) and strong acidic properties (modified by Al isomorphic substitution) of the as-prepared zeolitic catalysts.

The rotational spectra of four isotopologues of the 1:1 complex between chloromethane and water revealed the presence of only one rotamer in a pulsed jet expansion. The two subunits are linked through two weak hydrogen bonds, O-H⋅⋅⋅Cl (R(H⋅⋅⋅Cl) =2.638(2) Å) and C-H⋅⋅⋅O (R(H⋅⋅⋅O) =2.501(2) Å), forming a five-membered ring. All transitions display the hyperfine structure due to the (35)Cl (or (37)Cl) nuclear quadrupole effects. Dynamical features in the spectrum are caused by two large-amplitude motions. Each component line appears as an asymmetric doublet with a relative intensity ratio of 1:3. The splittings led to the determination of barrier to internal rotation of water around its symmetry axis, V(2) =320(10) cm(-1). Finally, an unexpected small value of the inertial defect (-0.96 uÅ(2) rather than -3.22 uÅ(2)) allowed the estimation of the barrier to the internal rotation of the CH(3) group, V(3) ≈8 cm(-1).

The production of efficient and low-cost electrocatalysts for the oxygen reduction reaction (ORR) is one of the key issues for the extensive commercialization of fuel cells. In this paper, we describe a facile one-pot hydrothermal synthesis route to in situ grow spinel NiFe2O4 nanoparticles onto the graphene nanosheets which were produced in advance by a scalable solvothermal reduction of chloromethane and metallic potassium. The resultant NiFe2O4/graphene nanohybrid exhibits superior electrocatalytic activity for the ORR to pure graphene nanosheets and unsupported NiFe2O4 nanoparticles, which mainly favours a desirable direct 4e− reaction pathway during the ORR process. Meanwhile, the NiFe2O4/graphene nanohybrid exhibits the outstanding long-term stability for the ORR, outperforming the commercial 20 wt% Pt/C based on the current–time chronoamperometric test. The excellent catalytic activity and stability of NiFe2O4/graphene nanohybrid are ascribed to the strong coupling and synergistic effect between NiFe2O4 nanoparticles and graphene nanosheets.

Zinc-modified alumina catalysts for methyl chloride synthesis were prepared with varying zinc loadings: from 2.4 to 21.1 wt%. The influence of the zinc loading, zinc precursor and the pH of the impregnation on the physico-chemical properties of the catalyst, and on the catalyst activity and selectivity for methyl chloride (MeCl) synthesis was investigated. The prepared catalysts were thoroughly characterized by FTIR, TEM, physisorption and EDX. On the alumina surface, both molecular and bulk zinc species are created upon zinc loading. The surface area of the catalyst decreases steadily with zinc loading. Bulk zinc species dominate on the catalyst starting at a zinc loading of 9.4 wt% and the amount of Lewis acid sites (LAS) decreases. A shift in the acid site type takes place upon zinc modification. Sites assigned to stronger LAS are eliminated while zinc-based weaker acid sites started to predominate. The shift in acidity increases the selectivity and activity of methyl chloride synthesis, which was demonstrated in a series of experiments in a laboratory-scale fixed bed reactor.

To enhance the process of phenyltrichlorosilane synthesis using gas phase condensation, a series of chloralkanes were introduced. The influence of temperature and chloralkane amount on the synthesis was studied based on the product distribution from a tubular reactor. The promoting effect of chloralkane addition was mainly caused by the chloralkane radicals generated by the dissociation of C–Cl bond. The promoting effect of the chloromethane with more chlorine atoms was better than those with less chlorine atoms. Intermediates detected from the reactions with isoprene and bromobenzene demonstrated that both trichlorosilyl radical and dichlorosilylene existed in the reaction system in the presence of chloralkanes. A detailed reaction scheme was proposed.

SAPO-34 molecular sieves were synthesized in the presence of soluble starch, sodium dodecyl sulfate and cetyltrimethylammonium bromide as the additives under hydrothermal conditions, and the differences stemmed from the additives among all obtained SAPO-34 samples were characterized by XRD, SEM, BET, NH3-TPD and TG. Compared with the conventional SAPO-34 sample, the SAPO-34 samples modified by sodium dodecyl sulfate and cetyltrimethylammonium bromide showed less crystalline order, enlarged mesopore volume and external surface area and a reduction in total acidity amounts. Meanwhile, the SAPO-34 modified by soluble starch exhibited more total acidity amounts than the conventional SAPO-34 samples. The SAPO-34 samples modified by sodium dodecyl sulfate and cetyltrimethylammonium bromide showed better catalytic stability and less carbon deposition than the conventional SAPO-34 catalyst in the conversion of chloromethane to olefins due to the reduction in total acid sites and the increasing mesopore volume. The overall results of this study demonstrate that it is an effective way to modify the SAPO-34 molecular sieve with sodium dodecyl sulfate and cetyltrimethylammonium bromide as the additives for improving the SAPO-34 catalyst stability in the transformation of chloromethane to olefins.

The first extraterrestrial detections of a member of the organohalogen family of molecules have been made towards comet Churyumov–Gerasimenko and low-mass protostar IRAS 16293-2422. Chloromethane, considered to be a biomarker, can form efficiently abiotically.

Conversion of chloromethane to olefins over SAPO-34 and HZSM-22 catalysts has been investigated at various temperatures. SAPO-34 showed higher activity and better stability than HZSM-22 catalyst. Ethylene and propylene were the main products over SAPO-34, whereas the main products over HZSM-22 were propylene, butylene, and C5+ alkanes in this conversion. Polymethylated benzenes and methylnaphthalene were the main components of coke species confined in the spent SAPO-34 catalyst. However, long-chain alkanes were the main species trapped in the spent HZSM-22 catalyst in the initial period, and many polymethylated benzenes emerged with growing time on stream. The differences in selectivity and coke species from both spent catalysts suggested that the conversion of chloromethane to olefins was greatly influenced by the topology structure of zeolite catalyst and that olefin methylation and cracking might be an important route followed over the HZSM-22 catalyst.

Hierarchical SAPO-34 molecular sieve was successfully synthesized by hydrothermal crystallization method with cetyltrimethyl ammonium bromide as mesoporous generating agent. The influence of different addition amounts of CTAB on the crystalline structures, morphology features, textural properties and acidity of hierarchical SAPO-34 catalysts were characterized by XRD, SEM, BET and NH3-TPD techniques. The results exhibit that the crystal size, mesoporous structure and the total acid amounts of hierarchical SAPO-34 are affected greatly by the molar ratio of CTAB/Al2O3. The selectivity of light olefins (ethane and propylene) can achieve 80 % for all SAPO-34 samples tested in the conversion of chloromethane to light olefins. Compared with the conventional SAPO-34, the hierarchical SAPO-34 samples show better catalytic stability and less carbon deposit in this conversion due to the reduction in total acid sites and the increasing mesopore volume.

Theoretical determination of electron impact total ionization cross sections for chloromethane (CH2Cl2, CHCl3), bromomethane (CH2Br2, CHBr3, and CBr4) and some mono chloroalkane (C2H5Cl, 1-C3H7Cl and 1-C4H9Cl) molecules in gaseous ground state are reported over the energy range from ionization threshold to 5 keV. Here, the target molecule is represented as an aggregate of scattering centres, which is assumed to scatter the electron independently. Hence, an approximation called group additivity rule is adopted for the determination of cross sections. Spherical complex optical potential formalism is employed to calculate the inelastic cross section for the constituent scattering centres. Sum of the inelastic cross sections of the constituent centres gives the molecular total inelastic cross section. Further, the total ionization cross section of the target molecule is derived from the molecular inelastic cross section using the complex scattering potential ionization contribution method. The results obtained are compared with previous measurements and theoretical values wherever available and satisfactorily good agreement is observed. The cross section predicted presently for CBr4 molecule is a maiden attempt.

The results from the Viking mission in the mid 1970s provided evidence that the martian surface contained oxidants responsible for destroying organic compounds. In 2008 the Phoenix Wet Chemistry Lab (WCL) found perchlorate ( ClO 4 - ) in three soil samples at concentrations from 0.5 to 0.7 wt%. The detection of chloromethane (CH3Cl) and dichloromethane (CH2Cl2) by the Viking pyrolysis gas chromatograph–mass spectrometer (GC–MS) may have been a result of ClO 4 - at that site oxidizing either terrestrial organic contaminates or, if present, indigenous organics. Recently, the Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL) Curiosity directly measured the presence of CH3Cl, CH2Cl2 and, along with measurements of HCl and oxygen, indirectly indicate the presence of ClO 4 - . However, except for Phoenix, no other direct measurement of the ClO 4 - anion in martian soil or rock has been made. We report here ion chromatographic (IC) and isotopic analyses of a unique sawdust portion of the martian meteorite EETA79001 that show the presence by mass of 0.6 ± 0.1 ppm ClO 4 - , 1.4 ± 0.1 ppm ClO 3 - , and 16 ± 0.2 ppm NO 3 - at a quantity and location within the meteorite that is difficult to reconcile with terrestrial contamination. The sawdust sample consists of basaltic material with a minor salt-rich inclusion in a mass ratio of ∼300:1, thus the salts may be 300 times more concentrated within the inclusion than the whole sample. The molar ratios of NO 3 - : ClO 4 - and Cl - : ClO 4 - , are very different for EETA79001 at ∼40:1 and 15:1, respectively, than the Antarctic soils and ice near where the meteorite was recovered at ∼10,000:1 and 5000:1, respectively. In addition, the isotope ratios for EETA79001 with δ15N = −10.48 ± 0.32‰ and δ18O = +51.61 ± 0.74‰ are significantly different from that of the nearby Miller Range blue ice with δ15N = +102.80 ± 0.14‰ and δ18O = +43.11 ± 0.64‰. This difference is notable, because if the meteorite had been contaminated with nitrate from the blue ice, the δ15N values should be the same. More importantly, the δ15N is similar to the uncontaminated Tissint Mars meteorite with δ15N = −4.5‰. These findings suggest a martian origin of the ClO 4 - , ClO 3 - and NO 3 - in EETA79001, and in conjunction with previous discoveries, support the hypothesis that they are present and ubiquitous on Mars. The presence of ClO 3 - in EETA79001 suggests the accompanying presence of other highly oxidizing oxychlorines such as ClO 2 - or ClO−, produced both by UV oxidation of Cl− and γ- and X-ray radiolysis of ClO 4 - . Since such intermediary species may contribute to oxidization of organic compounds, only highly refractory and/or well-protected organics are likely to survive. The global presence of ClO 4 - , ClO 3 - , and NO 3 - , has broad implications for the planet-wide water cycle, formation of brines, human habitability, organics, and life.

Host-guest complexes between cryptophane-A as host and dichloromethane and chloroform as guests are investigated using (1)H and (13)C NMR spectroscopy. Moreover, a related cryptophane, with the methoxy groups replaced by butoxy units (cryptophane-But), and its complexes with the same guests were also studied. Variable temperature spectra showed effects of chemical exchange between the free and bound guests, as well as of conformational exchange of the host. The guest exchange was studied quantitatively by exchange spectroscopy or line shape analysis. Extraction of kinetic and thermodynamic parameters led to the characterization of the affinity between guests and hosts. On the other hand, the host exchange was investigated by means of (13)C Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion which aims at the determination of the transverse relaxation rate R2, the inverse of the transverse relaxation time T2, as a function of the repetition of the π pulses in a CPMG train. The variation of the measured transverse relaxation rate with the repetition rate νCPMG indicated conformational exchange occurring on the microsecond-millisecond time scale. Structural information was obtained through measurements of cross-relaxation rates, both within the host and between the host and the guest protons. The NMR results were supported by DFT calculations.

To rationalize the driving factors in the competition of halogen bonding and hydrogen bonding, the complexes of the combined halogen-/hydrogen-bond donor difluoroiodomethane with the Lewis bases trimethylphosphine, dimethyl sulfide and chloromethane are studied. For all Lewis bases,ab initiocalculations lead to halogen- and hydrogen-bonded complexes. Fourier transform–IR experiments involving solutions of mixtures of difluoroiodomethane with trimethylphosphine(-d9) or dimethyl sulfide(-d6) in liquid krypton confirm the coexistence of a halogen-bonded and hydrogen-bonded complex. Also for solutions containing chloromethane, evidence of the formation of binary associations is found, but no definitive assignment of the multiple complex bands could be made. Using van't Hoff plots, the experimental complexation enthalpies for the halogen- and hydrogen-bonded complex of difluoroiodomethane with trimethylphosphine are determined to be −15.4 (4) and −10.5 (3) kJ mol−1, respectively, while for the halogen- and hydrogen-bonded complexes with dimethyl sulfide, the values are −11.3 (5) and −7.7 (6) kJ mol−1, respectively. The experimental observation that for both trimethylphospine and dimethyl sulfide the halogen-bonded complex is more stable than the hydrogen-bonded complex supports the finding that softer Lewis bases tend to favor iodine halogen bonding over hydrogen bonding.

[1] A single scoop of the Rocknest aeolian deposit was sieved (

International audience; Chloromethane (CH3 Cl) is a widely studied volatile halocarbon involved in the destruction of ozone in the stratosphere. Nevertheless, its global budget still remains debated. Stable isotope analysis is a powerful tool to constrain fluxes of chloromethane between various environmental compartments which involve a multiplicity of sources and sinks, and both biotic and abiotic processes. In this study, we measured hydrogen and carbon isotope fractionation of the remaining untransformed chloromethane following its degradation by methylotrophic bacterial strains Methylobacterium extorquens CM4 and Hyphomicrobium sp. MC1, which belong to different genera but both use the cmu pathway, the only pathway for bacterial degradation of chloromethane characterized so far. Hydrogen isotope fractionation for degradation of chloromethane was determined for the first time, and yielded enrichment factors (ε) of -29‰ and -27‰ for strains CM4 and MC1, respectively. In agreement with previous studies, enrichment in (13) C of untransformed CH3 Cl was also observed, and similar isotope enrichment factors (ε) of -41‰ and -38‰ were obtained for degradation of chloromethane by strains CM4 and MC1, respectively. These combined hydrogen and carbon isotopic data for bacterial degradation of chloromethane will contribute to refine models of the global atmospheric budget of chloromethane.

Computational simulations for chloromethane hydrolysis have been performed using hybrid quantum-mechanical/molecular-mechanical methods with explicit solvation by large numbers of water molecules. In the first part of the paper, we present results for 2° 2H3, 1° 14C, and 1° 37Cl kinetic isotope effects (KIEs) at 298 K with both the AM1/TIP3P and B3LYP/6-31G* QM methods for the nucleophile H2O and electrophile CH3Cl surrounded by 496 solvating TIP3P water molecules. An initial Hessian computed for a subset of this system including up to 104 MM water molecules was reduced in size by successive deletion of rows and columns, and KIEs were evaluated for each. We suggest that accurate calculations of KIEs in solvated systems should involve a subset Hessian including the substrate together with any solvent atoms making specific interactions with any isotopically substituted atom. In the second part of the paper, the ensemble-averaged 2° α-2H3 KIE calculated with the B3LYP/6-31+G(d,p)/TIP3P method is shown to be in good agreement with experiment. This comparison is meaningful because it includes consideration of uncertainties owing to sampling of a range of representative thermally accessible solvent configurations. We also present ensemble-averaged 14C and 37Cl KIEs which have not as yet been determined experimentally. Copyright © 2013 John Wiley & Sons, Ltd.

Ab initio calculations at the G3 level were used in a theoretical description of the kinetics and mechanism of the chlorine abstraction reactions from mono-, di-, tri- and tetra-chloromethane by chlorine atoms. The calculated profiles of the potential energy surface of the reaction systems show that the mechanism of the studied reactions is complex and the Cl-abstraction proceeds via the formation of intermediate complexes. The multi-step reaction mechanism consists of two elementary steps in the case of CCl4 + Cl, and three for the other reactions. Rate constants were calculated using the theoretical method based on the RRKM theory and the simplified version of the statistical adiabatic channel model. The temperature dependencies of the calculated rate constants can be expressed, in temperature range of 200–3,000 K as\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \begin{array}{*{20}c} {k\left( {\mathrm{C}{{\mathrm{H}}_3}\mathrm{C}\mathrm{l}+\mathrm{Cl}} \right) = 2.08\times {10^{-11 }}\times {{{\left( {{{\mathrm{T}} \left/ {300 } \right.}} \right)}}^{1.63 }}\times\exp \left( {{-12780 \left/ {\mathrm{T}} \right.}} \right)\ }{\mathrm{c}{{\mathrm{m}}^3}\mathrm{molecul}{{\mathrm{e}}^{-1 }}{{\mathrm{s}}^{-1 }}} \\ {k\left( {\mathrm{C}{{\mathrm{H}}_2}\mathrm{C}{{\mathrm{l}}_2}+\mathrm{Cl}} \right) = 2.36\times {10^{-11 }}\times {{{\left( {{{\mathrm{T}} \left/ {300 } \right.}} \right)}}^{1.23 }}\times\exp \left( {{-10960 \left/ {\mathrm{T}} \right.}} \right)}{\mathrm{c}{{\mathrm{m}}^3}\mathrm{molecul}{{\mathrm{e}}^{-1 }}{{\mathrm{s}}^{-1 }}} \\ {k\left( {\mathrm{C}\mathrm{HC}{{\mathrm{l}}_3}+\mathrm{Cl}} \right) = 5.28\times {10^{-11 }}\times {{{\left( {{{\mathrm{T}} \left/ {300 } \right.}} \right)}}^{0.97 }}\times\exp \left( {{-9200 \left/ {\mathrm{T}} \right.}} \right)}{\mathrm{c}{{\mathrm{m}}^3}\mathrm{molecul}{{\mathrm{e}}^{-1 }}{{\mathrm{s}}^{-1 }}} \\ {k\left( {\mathrm{C}\mathrm{C}{{\mathrm{l}}_4}+\mathrm{Cl}} \right) = 1.51\times {10^{-10 }}\times {{{\left( {{{\mathrm{T}} \left/ {300 } \right.}} \right)}}^{0.58 }}\times \exp \left( {{-7790 \left/ {\mathrm{T}} \right.}} \right)}{\mathrm{c}{{\mathrm{m}}^3}\mathrm{molecul}{{\mathrm{e}}^{-1 }}{{\mathrm{s}}^{-1 }}} \\ \end{array} $$\end{document} The rate constants for the reverse reactions CH3/CH2Cl/CHCl2/CCl3 + Cl2 were calculated via the equilibrium constants derived theoretically. The kinetic equations\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \begin{array}{*{20}c} {k\left( {\mathrm{C}{{\mathrm{H}}_3}+\mathrm{C}{{\mathrm{l}}_2}} \right) = 6.70\times {10^{-13 }}\times {{{\left( {{{\mathrm{T}} \left/ {300 } \right.}} \right)}}^{1.51 }}\times \exp \left( {{270 \left/ {\mathrm{T}} \right.}} \right)}{\mathrm{c}{{\mathrm{m}}^3}\mathrm{molecul}{{\mathrm{e}}^{-1 }}{{\mathrm{s}}^{-1 }}} \\ {k\left( {\mathrm{C}{{\mathrm{H}}_2}\mathrm{C}\mathrm{l}+\mathrm{C}{{\mathrm{l}}_2}} \right) = 7.34\times {10^{-14 }}\times {{{\left( {{{\mathrm{T}} \left/ {300 } \right.}} \right)}}^{1.43 }}\times \exp \left( {{390 \left/ {\mathrm{T}} \right.}} \right)}{\mathrm{c}{{\mathrm{m}}^3}\mathrm{molecul}{{\mathrm{e}}^{-1 }}{{\mathrm{s}}^{-1 }}} \\ {k\left( {\mathrm{C}\mathrm{HC}{{\mathrm{l}}_2}+\mathrm{C}{{\mathrm{l}}_2}} \right) = 6.81\times {10^{-14 }}\times {{{\left( {{{\mathrm{T}} \left/ {300 } \right.}} \right)}}^{1.60 }}\times \exp \left( {{-370 \left/ {\mathrm{T}} \right.}} \right)}{\mathrm{c}{{\mathrm{m}}^3}\mathrm{molecul}{{\mathrm{e}}^{-1 }}{{\mathrm{s}}^{-1 }}} \\ {k\left( {\mathrm{C}\mathrm{C}{{\mathrm{l}}_3}+\mathrm{C}{{\mathrm{l}}_2}} \right) = 1.43\times {10^{-13 }}\times {{{\left( {{{\mathrm{T}} \left/ {300 } \right.}} \right)}}^{1.52 }}\times \exp \left( {{-550 \left/ {\mathrm{T}} \right.}} \right)}{\mathrm{c}{{\mathrm{m}}^3}\mathrm{molecul}{{\mathrm{e}}^{-1 }}{{\mathrm{s}}^{-1 }}} \\ \end{array} $$\end{document}allow a very good description of the reaction kinetics. The derived expressions are a substantial supplement to the kinetic data necessary to describe and model the complex gas-phase reactions of importance in combustion and atmospheric chemistry.

Four precious metals supported on activated carbon are compared as catalysts in the gas-phase hydrodechlorination (HDC) of chloromethanes. The intrinsic activity or turnover frequency (TOF) of the catalysts follows the order Pd/C > Rh/C > Pt/C > Ru/C in the HDC of dichloromethane (DCM) while the sequence Pd/C > Pt/C > Rh/C > Ru/C was found for the HDC of chloroform (TCM). High selectivities to non-chlorinated products were obtained in all cases except for the HDC of TCM with Rh/C and Ru/C where the selectivity to DCM greatly depends on the operating conditions. A wider diversity of non-chlorinated hydrocarbons was obtained as reaction products with these two catalysts, especially in the HDC of TCM, favoring the formation of carbonaceous deposits which provoked a marked deactivation of the catalysts. In contrast, CH4 was the only non-chlorinated product obtained with the Pt/C catalysts which showed by far the highest stability. Different reaction pathways were found depending on the catalyst and the starting chloromethane. The different reactivity of the metals is explained in terms of their different electronic structure and the physicochemical properties of the catalysts.

We propose a mechanism by which chloromethane and dichloromethane decomposition reaction occurs on the surfaces of graphene. To this end we have performed calculations on the graphene surface with metal adsorption on the sheet on the opposite side of reactions to reduce the formation of free-radical intermediates.

Stable isotope techniques are increasingly applied to study atmospheric budgets of methyl halides. Here we use compound specific thermal conversion isotope ratio mass spectrometry to measure the stable hydrogen isotope values of methyl chloride ( δ 2 H CH 3 Cl ) released thermally from dried leaves of halophyte plants collected from different geographical locations. We developed an automated purification and pre-concentration unit to enable measurement of δ 2 H CH 3 Cl from samples (100 ml) when mixing ratios were as low as 1 ppmv. Even though this is considerably higher than normal atmospheric mixing ratios this unit enabled measurement of the δ2H values of CH3Cl released during heating of samples at temperatures ranging from 30 to 300 °C. No substantial changes of δ 2 H CH 3 Cl values were observed over this temperature range. However, the δ 2 H CH 3 Cl values of all plants examined were strongly depleted (−178 ± 34‰) relative to the δ2H values of their modelled meteoric water, but differ only by 1–50‰ from those observed for their methoxyl groups. Our results indicate that plant methoxyl groups are an important precursor of the methyl group for CH3Cl thermally emitted from lyophilised and homogenized dry halophyte leaves. Furthermore, the thermal reaction producing CH3Cl did not show a substantial kinetic hydrogen isotope fractionation between CH3Cl and precursor methoxyl groups over the temperature range investigated. Moreover, we found a moderate linear correlation (R2 = 0.37) for the relationship between δ 2 H CH 3 Cl values released from halophytes and the δ2H values of modelled precipitation at their geographical locations. As CH3Cl emissions from terrestrial vegetation, including senescent and dry plants and biomass burning, are considered to provide a substantial fraction of the global emissions our findings are important when establishing a global hydrogen isotope model for atmospheric CH3Cl.

National Basic Research Program of China [2010CB732303]; Natural Science Foundation of China [20923004, 21033006, 21161130522]; Program for Changjiang Scholars and Innovative Research Team in University [IRT1036]; Key Scientific Project of Fujian Province [2009HZ0002-1]

This study evaluates the effects of a sampling strategy that includes the sampling season, time period, ambient environment, and location on determining the concentrations and species of ambient volatile organic compounds (VOCs) that may affect children in primary schools. Air samples were collected from playgrounds in primary schools, with four sites near an oil refinery plant in Taoyuan and two sites in Zhongli (one site near a bus terminal and the other site in a suburban area) in Taiwan. The samples were obtained on eight occasions from August 2010 to June 2011. One sample was collected from 09:00 to 11:00 and the other was collected from 13:00 to 15:00 on each occasion using passive flow controller canisters (40 mL min−1 flow rate) assembled with silica-coated stainless steel. The United States Environmental Protection Agency Method TO-15 with Photochemical Assessment Monitoring System and Urban Air Toxics standards was used to analyze the samples. The ratios of benzene, toluene, ethylbenzene, and xylenes (BTEXs) were also estimated. This study found that the sampling location and wind direction are the main determinants to monitor the concentrations and species of ambient VOCs, and the effects from the sampling season and time period are minor. Alkane, ketone, and aromatics have been ranked as the top three categories with high concentrations, and toluene, 2-butanone, and acetone have been detected with the highest concentrations among the investigated VOCs. Several VOCs emitted from stationary sources, including propane, isoprene, n-decane, chloromethane, chloroethene, chloroethane and 1,2-dichloroethane, were detected only in Taoyuan. Higher concentrations of VOC species associated with automobiles and common community sources were detected in Zhongli but not in Taoyuan. Among BTEXs ratios, toluene/ethylbenzene ratios were as high as 31.52 (standard deviation [S.D.] = 13.53) in Taoyuan and 13.66 (S.D. = 3.87) in Zhongli. Toluene/benzene ratios were as high as 15.7 in Taoyuan and 4.30 in Zhongli. This study suggests that the susceptible population exposed to ambient VOCs should be considered in planning public service facilities and the presence of VOCs should be investigated regularly.

Two sets of zinc-iron and copper-iron mixed (hydr)oxides were prepared by a simple co-precipitation method. Either nitrate or chloride was a source of the metals. The decontamination ability of the materials was tested in closed vials saturated with vapors of 2-chloroethyl ethyl sulfide (CEES) or dimethyl chlorophosphate (DMCP), a blister agent and a nerve agent surrogate, respectively. In both cases, the weight uptakes on the mixed oxides were superior to the ones reported for the pure metal oxides or hydroxides. When exposed to CEES for 5 days, zinc-iron (hydr)oxides show much higher activity than the copper-iron ones. The products of reactions in the vessel headspace were investigated by GC/MS and on the surface by FTIR. Ethyl vinylsulfide and chloromethane are the main products of the reactive adsorption of CEES and DMCP, respectively. This indicates that CEES is mainly degraded by dehydrochlorination and DMCP- by hydrolysis.

Chloromethane (CH3Cl) is a volatile organic compound responsible for over 15% of stratospheric ozone degradation due to chlorinated compounds. It is mainly produced by living and decaying plants. Bacteria utilizing CH3Cl as sole carbon and energy source for growth were shown to be involved in the filtering of CH3Cl emissions to the atmosphere. This biological process remains to be quantified in the environment, especially for forest soil, a major CH3Cl sink. The cmuA gene is used as a biomarker of bacterial CH3Cl degradation in environmental studies. It encodes a CH3Cl methyltransferase essential for bacterial growth by the cmu (chloromethane utilization) pathway for growth with CH3Cl and the only one characterized so far. My thesis project had a double aim: i) In depth studies of CH3Cl adaptation of a model methylotrophic bacterium, Methylobacterium extorquens strain CM4; ii) Exploration of bacterial CH3Cl-utilizers in forest. An RNAseq study of strain CM4 has shown that growth with CH3Cl leads to a difference of transcription of 137 genes in its 6.2 Mb genome compared to growth with methanol (CH3OH). Among those, genes of the cmu pathway and other genes involved in the metabolism of essential cofactors for CH3Cl utilization by this pathway, are all plasmid pCMU01-encoded. Paralogous genes located on the chromosome were not differentially expressed. On the other hand, other chromosomal genes potentially involved in extruding protons generated during CH3Cl deshalogenation (hppA), NADP+ regeneration (pnt), or in the cofactor tetrahydrofolate metabolism (gcvPHT) were differentially expressed. The diversity of CH3Cl-degrading bacteria in forest soil of the German natural park of Steigerwald was studied in microcosms using stable isotope probing. Microorganisms able to assimilate labeled [13C]- CH3Cl incorporate this heavy carbon isotope in their DNA. Sequence analysis of the PCR-amplified 16S RNA encoding gene from [13C]-DNA fractions uncovered phylotypes of the genus Methylovirgula and of the order of the Actinomycetales, which were not associated with bacterial CH3Cl degradation so far. In contrast, PCR-amplified sequences of cmuA and other genes of methylotrophic metabolism were closely related to known CH3Cl-degrading isolates. These results suggest that bacteria containing genes of the cmu pathway acquired by horizontal gene transfer as well as bacteria lacking the cmu pathway contribute to biological filtering of CH3Cl in forest soil. Future experiments coupling molecular and culture methods will aim to discover new CH3Cl-degrading pathways and to characterize the abundance and diversity of CH3Cl-degradation metabolism in soil and other environmental compartments., Le chlorométhane (CH3Cl) est un composé organique volatile responsable de plus de 15 % de la dégradation de l’ozone stratosphérique due aux composés chlorés. Il est produit majoritairement par les plantes vivantes ou en décomposition. Les bactéries capables d’utiliser le CH3Cl comme source de carbone pour leur croissance peuvent jouer un rôle de filtre dans les émissions de CH3Cl vers l'atmosphère. Ce processus biologique reste à quantifier dans l'environnement, notamment pour les sols forestiers considérés comme un puits majeur de ce composé.Dans les études environnementales, le gène cmu A est utilisé comme biomarqueur de la dégradation bactérienne du CH3Cl. Il code une chlorométhane méthyltransférase essentielle à la croissance bactérienne avec le CH3Cl parla voie cmu (pour chloromethane utilisation), la seule caractérisée à ce jour. Mon projet de thèse avait un double objectif : i) l’approfondissement des connaissances de l’adaptation au CH3Cl chez une bactérie méthylotrophe modèle, Methylobacterium extorquens CM4; ii) l’exploration de la diversité des bactéries CH3Cl-dégradantes de sols forestiers. L’étude RNAseq chez la souche CM4 a montré que la croissance avec le CH3Cl s'accompagne de différences dans la transcription de 137 gènes de son génome (6.2 Mb) par rapport à sa croissance sur le méthanol (CH3OH). Les gènes de la voie cmu, ainsi que d’autres gènes impliqués dans le métabolisme de cofacteurs essentiels à l’utilisation du CH3Cl par cette voie et eux aussi portés par le plasmide pCMU01 de la souche, en font partie. Les paralogues de ces gènes localisés sur le chromosome ne sont quant à eux pas différentiellement exprimés. En revanche, d’autres gènes du chromosome, potentiellement impliqués dans l’excrétion de protons produits lors de la déshalogénation (hppA), la régénération du NADP+ (pnt), ou le métabolisme du cofacteur tétrahydrofolate(gènes gcvPHT), le sont. L’étude de la diversité des bactéries CH3Cl-dégradantes de sol forestier de la réserve naturelle de Steigerwald (Allemagne) a été réalisée sur des microcosmes par une approche de « Stable Isotope Probing ». Les microorganismes capables d’assimiler le CH3Cl marqué au [13C] incorporent cet isotope lourd du carbone dans leur ADN. L'analyse des séquences amplifiées par PCR des gènes codant l’ARN 16S des fractions d'ADN enrichies en [13C] a permis de mettre en évidence de nouveaux phylotypes, du genre Methylovirgula et de l’ordre des Actinomycetales, distincts de ceux auxquelles les souches dégradant le CH3Cl isolées jusqu'ici sont affiliées. En revanche, les séquences du gène cmuA et d’autres gènes du métabolisme méthylotrophe obtenues par PCR à partir de l'ADN enrichi en [13C] sont très proches de celles des souches CH3Cl-dégradantes connues. Les résultats obtenus suggèrent ainsi que des bactéries ayant acquis par transfert horizontal les gènes de dégradation de la voie cmu ou ne possédant pas de gène cmuA contribuent au filtrage biologique du CH3Cl des sols forestiers. A l'avenir, le couplage de différentes méthodes moléculaires et des approches culturales visera à découvrir de nouvelles voies microbiennes de l’utilisation du CH3Cl, et à caractériser l’abondance et la diversité des métabolismes impliqués dans la dégradation du CH3Cl dans les sols et d'autres compartiments environnementaux.

More than 5000 natural organohalogen compounds have been identified. In terrestrial environments, the bulk of the organochlorine is locked up in humic polymers, collectively accounting for a global organochlorine storage of several million Gg. Natural sources are primarily responsible for the global budget of chloromethane and chloroform. Basidiomycete fungi involved in the decomposition of forest litter produce large quantities of chlorinated phenolic methyl ethers. In marine environments naturally occurring chlorinated and brominated bipyrroles as well as methoxypolybrominated phenyl ethers biomagnify in sea mammals. There are at least five distinct halogenating enzyme systems: (1) methyl transferases; (2) heme haloperoxidases; (3) vandadium haloperoxidases; (4) flavin-dependent halogenases and (5) α-ketoglutarate/Fe(II) dependent halogenases. Natural halogenated phenolic metabolites are subject to biotransformation including O-demethylation and organohalide respiration. Naturally occurring phenolics are also polymerized by oxidative enzymes to dioxins and chlorohumus.

Construction of accurate lineshape models for chlorosubstituted hydrocarbons is challenging. In this account the problem has been investigated thoroughly for the chloromethane series, CH4−nCln, n = 1–4, using high-resolution experimental data and extensive theoretical calculations. The C Cl bond contraction following ionization is a key parameter for a quantitative description of the vibrational excitation for all four molecules. We determine this quantity accurately for the title molecules and also propose approximate approaches that may applied to larger molecules. Having developed accurate vibrational lineshape models as well as reliable estimates of the instrumental broadening in each case, the carbon 1s hole lifetime broadening is determined from a fit to the experimental spectrum for each molecule. The resulting values for the lifetime broadening are 88 ± 5 meV for CH3Cl, 80 ± 5 meV for CH2Cl2, 74 ± 5 meV for CHCl3 and 62 ± 5 meV for CCl4. The lifetime widths decrease systematically with the number of chlorine substituents and correlate excellently with the valence occupancy of the core-ionized carbon. This indicates that the one-center model for Auger decay of the core hole is valid for the present series of molecules.

Using all-atom molecular dynamics simulations, the multilayer adsorption of two single-carbon alkane analogues—methane (CH4) and chloromethane (CH3Cl)—in the liquid phase on a metallic substrate (m...

A novel near-infrared-emitting binuclear platinum complex of (piq) 2 Pt 2 (μ-C 8 OXT) 2 was synthesized and characterized, in which piq is 1-phenylisoquinolinato and C 8 OXT is a bridging ancillary ligand of 5-(4-octyloxyphenyl)-1,3,4-oxadiazole)-2-thiol. Its optophysical, electrochemical and electroluminescent characteristics were primary studied. This binuclear platinum complex exhibited an intense UV absorption at about 493 nm from the metal–metal-to-ligand charge transfer transition and a bright near-infrared emission at 721 nm in chloromethane. Using (piq) 2 Pt 2 (μ-C 8 OXT) 2 as a single dopant, its single-emissive-layer polymer light-emitting devices presented a high-efficiency near-infrared emission peaked at 702 nm with the maximum external quantum efficiency of 6.3% at 7.6 mA cm −2 . This work provides an efficient approach to realize high-efficiency near-infrared emission by binuclear platinum complexes.

N,N-Dialkylamino(diphenylphosphoryl)chloromethanes, a new type of organophosphorus compounds, were synthesized. On dissolving in polar and low polar solvents, N,N-dialkylamino(diphenylphosphoryl)chloromethanes dissociate spontaneously with the P—C bond cleavage to form the diphenylphosphinite anion Ph2PO−. This was confirmed by the reaction of N,N-dimethylamino(diphenylphosphoryl)chloromethane with electrophilic substrates to form the corresponding addition or substitution products of Ph2PO−. The capability of spontaneous generating the diphenylphosphinite anion considers accessible N,N-dimethylamino(diphenylphosphoryl)chloromethane as a synthetic equivalent of the diphenylphosphinite anion.

National Basic Research Program of China [2010CB732303]; NSF of China [21033006, 20873110, 20923004]

Tetrachloroethene (PCE) and carbon tetrachloride (CT) were simultaneously transformed in a packed column that was bioaugmented with the Evanite culture (EV). The data presented here have been obtained over a period of 1930 days. Initially the column was continuously fed synthetic groundwater with PCE (0.1 mM), sulfate (SO 42 −) (0.2 mM) and formate (2.1 mM) or lactate (1.1 mM), but not CT. In these early stages of the study the effluent H 2 concentrations ranged from 7 to 19 nM, and PCE was transformed to ethene (ETH) (81 to 85%) and vinyl chloride (VC) (11 to 17%), and SO 42 − was completely reduced when using either lactate or formate as electron donors. SO42 − reduction occurred concurrently with cis-DCE and VC dehalogenation. Formate was a more effective substrate for promoting dehalogenation based on electron donor utilization efficiency. Simultaneous PCE and CT tests found CT (0.015 mM) was completely transformed with 20% observed as chloroform (CF) and trace amounts of chloromethane (CM) and dichloromethane (DCM), but no methane (CH4 ) or carbon disulfide (CS 2). PCE transformation to ETH improved with CT addition in response to increases in H2 concentrations to 160 nM that resulted from acetate formation being inhibited by either CT or CF. Lactate fermentation was negatively impacted after CT transformation tests, with propionate accumulating, and H2 concentrations being reduced to below 1 nM. Under these conditions both SO42 − reduction and dehalogenation were negatively impacted, with sulfate reduction not occurring and PCE being transformed to cis-dichloroethene (c-DCE) (52%) and VC (41%). Upon switching to formate, H2 concentrations increased to 40 nM, and complete SO42 − reduction was achieved, while PCE was transformed to ETH (98%) and VC (1%), with no acetate detected. Throughout the study PCE dehalogenation to ethene was positively correlated with the effluent H2 concentrations.

On the line of a previous work on the spectral properties of some of heteroaryl chalcone, the effect of medium acidity and photoreactivity of 3-(4-dimethylamino-phenyl)-1-(2,5-dimethyl-thiophen-3-yl)-propenone (DDTP) has been investigated in dimethylformamide and in chloromethane solvents such as methylenechloride, chloroform and carbon tetrachloride. The dye solution (ca. 5×10 －4

The size and shape of CdSe nanorods, CdSe tetrapods, and CdS nanowires were tailored by chemical and photochemical etchings in chloromethane solvents. Nanocrystals were synthesized by colloidal growth, and their sizes and shapes were visualized by transmission electron microscopy before and after etching. Crystal structures were confirmed by X-ray diffraction, and optical properties were monitored during etching. Chemical etching with tributylphosphine preferentially shortens the length of nanocrystals, whereas photochemical etching with both primary alkylamine and tributylphosphine reduces the diameter more than the length. The surface of etched nanocrystals was characterized by X-ray photoelectron spectroscopy, and the etching products dissolved in solvent were analyzed by matrix-free laser desorption ionization mass spectrometry. Spectroscopic results suggest that the chloride ion is the active species: Chloride ions are generated either by chemical activation of chloromethane solvents with tributylpho...