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Stable isotopes of chlorine have great application potential due to the widespread occurrence of the chlorine anion in water, minerals, living organisms and the environment. In most studies, the chloride ion from the samples is converted to chloromethane, which is then analysed isotopically using a mass spectrometer. In the present study, a new design for a chloromethane preparation line is proposed. In particular, the new chloromethane preparation line uses a new system for injecting iodomethane into the preparation system, as well as ampoules with Teflon valves and the u-shaped freezers. These improvements reduced the preparation time to about 1 h, and also achieved a decent measurement uncertainty of 0.05 permil. [ABSTRACT FROM AUTHOR]

Abstract Background Chloromethane (CH3Cl) is the most abundant halogenated organic compound in the atmosphere and substantially responsible for the destruction of the stratospheric ozone layer. Since anthropogenic CH3Cl sources have become negligible with the application of the Montreal Protocol (1987), natural sources, such as vegetation and soils, have increased proportionally in the global budget. CH3Cl-degrading methylotrophs occurring in soils might be an important and overlooked sink. Results and conclusions The objective of our study was to link the biotic CH3Cl sink with the identity of active microorganisms and their biochemical pathways for CH3Cl degradation in a deciduous forest soil. When tested in laboratory microcosms, biological CH3Cl consumption occurred in leaf litter, senescent leaves, and organic and mineral soil horizons. Highest consumption rates, around 2 mmol CH3Cl g−1 dry weight h−1, were measured in organic soil and senescent leaves, suggesting that top soil layers are active (micro-)biological CH3Cl degradation compartments of forest ecosystems. The DNA of these [13C]-CH3Cl-degrading microbial communities was labelled using stable isotope probing (SIP), and the corresponding taxa and their metabolic pathways studied using high-throughput metagenomics sequencing analysis. [13C]-labelled Metagenome-Assembled Genome closely related to the family Beijerinckiaceae may represent a new methylotroph family of Alphaproteobacteria, which is found in metagenome databases of forest soils samples worldwide. Gene markers of the only known pathway for aerobic CH3Cl degradation, via the methyltransferase system encoded by the CH3Cl utilisation genes (cmu), were undetected in the DNA-SIP metagenome data, suggesting that biological CH3Cl sink in this deciduous forest soil operates by a cmu-independent metabolism.

Copyright of Silicone Material is the property of Silicone Material Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Chlorine has important roles in the Earth's systems. In different forms, it helps balance the charge and osmotic potential of cells, provides energy for microorganisms, mobilizes metals in geologic fluids, alters the salinity of waters, and degrades atmospheric ozone. Despite this importance, there has not been a comprehensive summary of chlorine's geobiology. Here, we unite different areas of recent research to describe a biogeochemical cycle for chlorine. Chlorine enters the biosphere through volcanism and weathering of rocks and is sequestered by subduction and the formation of evaporite sediments from inland seas. In the biosphere, chlorine is converted between solid, dissolved, and gaseous states and in oxidation states ranging from −1 to +7, with the soluble, reduced chloride ion as its most common form. Living organisms and chemical reactions change chlorine's form through oxidation and reduction and the addition and removal of chlorine from organic molecules. Chlorine can be transported through the atmosphere, and the highest oxidation states of chlorine are produced by reactions between sunlight and trace chlorine gases. Partial oxidation of chlorine occurs across the biosphere and creates reactive chlorine species that contribute to the oxidative stress experienced by living cells. A unified view of this chlorine cycle demonstrates connections between chlorine biology, chemistry, and geology that affect life on the Earth. [ABSTRACT FROM AUTHOR]

The selective conversion of methane to high value‐added chemicals under mild conditions is of great significance for the commercially viable and sustainable utilization of methane but remains a formidable challenge. Herein, we report a strategy for efficiently converting methane to acetic acid via CH3Cl as an intermediate. Up to 99.3 % acetic acid and methyl acetate (AA+MA) selectivity was achieved over pyridine‐pretreated MOR (MOR‐8) under moderate conditions of 523 K and 2.0 MPa. Water, conventionally detrimental to carbonylation reaction over zeolite catalysts, was conducive to the production of AA in the current reaction system. In the 100 h continuous test with the MOR‐8 catalyst, the average AA+MA selectivity remained over 98 %. AA was formed by carbonylation of methoxy groups within 8‐membered rings of MOR followed by hydrolysis. This strategy provided an approach for highly efficient utilization of methane to oxygenates under mild reaction conditions. [ABSTRACT FROM AUTHOR]

Background: Chloromethane (CH3Cl) is the most abundant halogenated organic compound in the atmosphere and substantially responsible for the destruction of the stratospheric ozone layer. Since anthropogenic CH3Cl sources have become negligible with the application of the Montreal Protocol (1987), natural sources, such as vegetation and soils, have increased proportionally in the global budget. CH3Cl-degrading methylotrophs occurring in soils might be an important and overlooked sink. Results and conclusions: The objective of our study was to link the biotic CH3Cl sink with the identity of active microorganisms and their biochemical pathways for CH3Cl degradation in a deciduous forest soil. When tested in laboratory microcosms, biological CH3Cl consumption occurred in leaf litter, senescent leaves, and organic and mineral soil horizons. Highest consumption rates, around 2 mmol CH3Cl g−1 dry weight h−1, were measured in organic soil and senescent leaves, suggesting that top soil layers are active (micro-)biological CH3Cl degradation compartments of forest ecosystems. The DNA of these [13C]-CH3Cl-degrading microbial communities was labelled using stable isotope probing (SIP), and the corresponding taxa and their metabolic pathways studied using high-throughput metagenomics sequencing analysis. [13C]-labelled Metagenome-Assembled Genome closely related to the family Beijerinckiaceae may represent a new methylotroph family of Alphaproteobacteria, which is found in metagenome databases of forest soils samples worldwide. Gene markers of the only known pathway for aerobic CH3Cl degradation, via the methyltransferase system encoded by the CH3Cl utilisation genes (cmu), were undetected in the DNA-SIP metagenome data, suggesting that biological CH3Cl sink in this deciduous forest soil operates by a cmu-independent metabolism. [ABSTRACT FROM AUTHOR]

The adsorption of N2, O2, fluoromethane (CH3F), and chloromethane (CH3Cl) gases was explored onto a BeO nanotube (BeONT) by density functional theory calculations. N2, O2, and CH3F interact weakly with BeONT, so it cannot be employed as a sensor. Nevertheless, there is a considerable increase in the sensitivity and reactivity of the sheet through the CH3Cl approach. There is a reduction in the HOMO–LUMO gap of BeONT from 7.03 to 4.30 eV (~ − 38.8%) when CH3Cl is adsorbed, thereby increasing the electrical conductivity to a great extent. Hence, it is possible to convert the considerable change in conductivity into an electronic signal, which demonstrates the encouraging nature of BeONT as a sensor to detect CH3Cl. Additionally, the adsorption process reduces work function of BeONT to a great extent, which demonstrates that we can also employ it as a work function-type sensor for detecting CH3Cl among the mentioned molecules. The recovery time for the BeONT was calculated to be 18.6 s for CH3Cl desorption, representing a short recovery time. [ABSTRACT FROM AUTHOR]

The transformation of methane into high value‐added chemicals such as aromatics provides a more desired approach towards sustainable chemistry but remains a critical challenge due to the low selectivity of aromatics and poor stability. Herein, we first report a coupling reaction of CH3Cl and CO (CCTA) based on methane conversion, which achieves extremely high aromatics selectivity (82.2 %) with the selectivity of BTX up to ca. 60 % over HZSM‐5. The promoting effects have been demonstrated on other zeolites especially 10‐membered rings (10 MR) zeolites. Multiple characterizations show that 2,3‐dimethyl‐2‐cyclopentene‐1‐one (DMCPO) is generated from acetyl groups and olefins. Furthermore, isotopic labeling analysis confirms that CO is inserted into the DMCPO and aromatics rings. A new aromatization mechanism is proposed, including the formation of the above intermediates, which conspicuously weakens the hydrogen transfer reaction, leading to a considerable increase of aromatics selectivity and a dramatic drop in alkanes. [ABSTRACT FROM AUTHOR]

Methyl chloride (CH3Cl) is a naturally occurring, ozone-depleting trace gas and one of the most abundant chlorinated compounds in the atmosphere. CH3Cl was measured in air from the Taylor Dome ice core in East Antarctica to reconstruct an atmospheric record for the Holocene (11–0 kyr B.P.) and part of the last glacial period (50–30 kyr B.P.). CH3Cl variability throughout the Holocene is strikingly similar to that of atmospheric methane (CH4), with higher levels in the early and late Holocene, and a well-defined minimum during mid-Holocene. The sources and sinks of atmospheric CH3Cl and CH4 are located primarily in the tropics, and variations in their atmospheric levels likely reflect changes in tropical conditions. CH3Cl also appears to correlate with atmospheric CH4 during the last glacial period (50–30 kyr B.P.), although the temporal resolution of sampling is limited. The Taylor Dome data provide information about the range of natural variability of atmospheric CH3Cl and place a new constraint on the causes of past CH4variability.

We report the tunable conversion of chloromethane to olefins and aromatics using different metal-promoted zeolites as catalysts. Despite SAPO-34 was industrially used as catalysts for methanol to olefins reaction (MTO), the SAPO-34 based zeolites exhibited low activity and short lifetime when using chloromethane as the feed. Higher chloromethane conversion and longer catalyst lifetime were found on H-ZSM-5. The activity and product distribution can be improved by optimizing the reaction temperature and space velocity. Impregnating the H-ZSM-5 zeolite with 1 wt% and 5 wt% metal oxide as promoters significantly enhanced the conversion efficiency and altered the product distribution. The highest aromatics selectivity (38%) was obtained on the H-ZSM-5 zeolite promoted by 5 wt% Ni, whereas on 5 wt% Mg and 5 wt% Mn promoted H-ZSM-5, the aromatics selectivity is merely 5%. Therefore, different modified H-ZSM-5 could be used to convert chloromethane to either aromatics or olefin-heavy products. It was found that the aromatics yield is strongly correlated to the acidity of the H-ZSM-5 zeolite. [ABSTRACT FROM AUTHOR]

This work presents a comprehensive kinetic modeling study of the pyrolysis and oxidation of chloromethane. Theoretical calculations were performed for the decomposition reaction CH3Cl + M = CH3 + Cl + M and for a set of relevant H‐abstraction reactions (CH3Cl + R, R = Cl, Ḣ, ȮH, HȮ2, O2, Ö, ĊH3, Ċ2H3, Ċ2H5; CH4 + Cl, C2H6 + Cl, C2H4 + Cl, C2H2 + Cl). Comparison with previous experimental or theoretical determinations, when available, proved the appropriateness of the adopted protocols and the accuracy of the calculated rate constants. Previously developed subsets for CH3Cl and HCl/Cl2 were updated with the theoretical rate constants and combined with the CRECK C1–C3 mechanism, yielding a kinetic mechanism consisting of 143 species and 2347 reactions. The validation was performed through comparison with all the pyrolysis and oxidation measurements available for pure CH3Cl and its mixtures with CH4, H2, and CO/H2O. The kinetic discussion highlights the role of key reaction steps that have been theoretically investigated in this work and in previous efforts and sheds light on additional reaction pathways needing better assessments. [ABSTRACT FROM AUTHOR]

In this paper, a series of Al−Ti mixed oxides with different Al/Ti ratios are prepared by a simple sol‐gel method and they are used as active catalysts for selective dechlorination of dichloromethane to chloromethane. The Al−Ti mixed oxide catalyst with the same molar ratio of Al and Ti shows the highest activity in dechlorination of dichloromethane. The strong and abundant Lewis acid sites in the Al−Ti mixed oxides formed along with Al−O−Ti bondings are responsible for the high catalytic activity toward the selective dechlorination reaction in this work. From a kinetic study, the activation energy of this reaction over the optimum Al−Ti mixed oxide catalyst appears to be 59.4 kJ mol−1 based on Langmuir‐Hinshelwood model. The improved catalytic performance suggests that the Al−Ti mixed oxide could be used as the effective catalyst for the highly selective dechlorination of dichloromethane to chloromethane. [ABSTRACT FROM AUTHOR]

Chloromethane is an important reagent for methylations in the process industry. However, as a gas suspected of causing cancer, it is rarely used at laboratory scale. Therefore, a setup is presented here for studies in a laboratory under safe and reproducible conditions. The use of a microreactor guarantees high heat transfer rates and a low holdup of the reagent. As a proof‐of‐concept, the reaction of chloromethane with the secondary amine morpholine in aqueous solution is investigated. By applying elevated pressures, a liquid‐liquid system with enhanced solubility of chloromethane in the aqueous phase is accessible. [ABSTRACT FROM AUTHOR]

Ro-vibrational spectra of the ν 3 and ν 6 bands of chloromethane ( CH 3 Cl) were recorded in the 650–1130 cm − 1 range using a Fourier transform spectrometer at the AILES beamline of the SOLEIL synchrotron facility. Two isotopologues ( CH 3 35 Cl and CH 3 37 Cl) have been analyzed with the tensorial formalism developed in Dijon and a total of 6753 lines were assigned. We derived 23 tensorial parameters for the lines positions (4 for the ground state, 6 for ν 3 , and 13 for ν 6), and 7 for the lines intensities (4 for ν 3 , 3 for ν 6). From those parameters and self-broadening coefficients found in the literature, we simulated spectra of both isotopologues. The derived parameters were converted in the Watson formalism to be compared with a previous study. Using these results, we set up a new database of calculated chloromethane spectral lines (ChMeCaSDa). • High-resolution infrared spectroscopy of two bands of chloromethane. • Analysis of two isotopologues of chloromethane in the tensorial formalism. • Fit of the tensorial parameters for line positions and intensities. • Simulation of the spectra. • New database of calculated spectral lines (ChMeCaSDa). [ABSTRACT FROM AUTHOR]

Abstract Methyl Chloride (MeCl; Chloromethane) is a high production volume chemical (>1000 t/a) and is used as an industrial solvent. Based on cardiac lesions reported in developmental toxicity studies in mice, but not in rats, manufacturers decided to classify MeCl as a developmental toxicant, cat. 2. Recently, the European Chemical Agency required a developmental toxicity study in a non-rodent species. No developmental toxicity was observed in rabbits in the recently completed, GLP, OECD 414 guideline study. In view of the absence of cardiac effects in rats and rabbits, the purpose of this review is to consider whether the cardiac effects reported in mice should be considered real effects and, if so, their potential for relevance to humans. This paper provides substantive new evidence with data from a third species and shows that an evaluation of the integrated scientific evidence indicates the reported developmental cardiac effects in mice, if not an artifact, are unlikely to be relevant to humans. As such the classification of MeCl for developmental toxicity was reconsidered. Highlights • Cardiac lesions were reported in fetal mice following exposure to high concentrations of MeCl but were not replicated. • These lesions, viz. reduced number of papillary muscles, were reported in fetal mice but not in fetal rats or rabbits. • The normal anatomy and variability in appearance of tiny papillary muscles in the fetal mouse heart complicate evaluation. • Number, length, and shape of cardiac papillary muscles are reported to be variable in humans. • Integrated evidence indicates these cardiac effects in fetal mice, if not an artifact, are unlikely to be relevant to humans. [ABSTRACT FROM AUTHOR]

Abstract H-ZSM-35 with 2D channel intersections has been first found to be an effective catalyst over chloromethane transformation into propylene. Fluoride treatment is further introduced to improve the catalytic performance. With a proper concentration of fluoride treatment, the selectivity and yield of propylene can be enhanced significantly while a high propylene/ethylene ratio is achieved. Detailed characterizations demonstrate that dealumination caused by fluoride treatment results in a reduction in acidic sites, which is responsible for the improvement of catalytic performance. Graphical abstract Unlabelled Image Highlights • H-ZSM-35 is an effective catalyst for the conversion of chloromethane to propylene. • Fluoride treatment can enhance the catalytic performance of H-ZSM-35 significantly. • Fluoride treatment result in desilication and dealuminization to the framework. • The strong Brønsted acidic sites are reduced by the fluoride treatment. • Catalytic activity is improved by the suppression of hydrogen-transfer reactions. [ABSTRACT FROM AUTHOR]

Methane activation through oxychlorination is in the spotlight due to the relatively mild reaction conditions at atmospheric pressure and in the temperature range of 450-550 °C. Although CO2 is known to exhibit good activity for methane oxychlorination, significant amounts of by-products such as CO2, CO and carbon deposits are produced during the reaction over CO2. We investigated the effect of iron in FeOx/CO2 catalysts on methane oxychlorination. FeOx/CO2 with 3 wt% iron shows the maximum yield at 510 °C with 23% conversion of methane and 65% selectivity of chloromethane. XRD and H2 TPR results indicate that iron-cerium solid solution was formed, resulting in the production of more easily reduced cerium oxide and the suppression of catalysts sintering during the reaction. Furthermore, the selectivity of by-products decreased more significantly over FeOx/CO2 than cerium oxide, which can be attributed to the facilitation of HCl oxidation arising from the enhanced reducibility of the former sample. [ABSTRACT FROM AUTHOR]

Chloromethane (CH 3 Cl) is the most abundant halogenated trace gas in the atmosphere. It plays an important role in natural stratospheric ozone destruction. Current estimates of the global CH 3 Cl budget are approximate. The strength of the CH 3 Cl global sink by microbial degradation in soils and plants is under discussion. Some plants, particularly ferns, have been identified as substantial emitters of CH 3 Cl. Their ability to degrade CH 3 Cl remains uncertain. In this study, we investigated the potential of leaves from 3 abundant ferns ( Osmunda regalis , Cyathea cooperi , Dryopteris filix-mas ) to produce and degrade CH 3 Cl by measuring their production and consumption rates and their stable carbon and hydrogen isotope signatures. Investigated ferns are able to degrade CH 3 Cl at rates from 2.1 to 17 and 0.3 to 0.9 μg g dw −1 day − 1 for C. cooperi and D. filix-mas respectively, depending on CH 3 Cl supplementation and temperature. The stable carbon isotope enrichment factor of remaining CH 3 Cl was −39 ± 13‰, whereas negligible isotope fractionation was observed for hydrogen (−8 ± 19‰). In contrast, O. regalis did not consume CH 3 Cl, but produced it at rates ranging from 0.6 to 128 μg g dw −1 day − 1 , with stable isotope values of −97 ± 8‰ for carbon and −202 ± 10‰ for hydrogen, respectively. Even though the 3 ferns showed clearly different formation and consumption patterns, their leaf-associated bacterial diversity was not notably different. Moreover, we did not detect genes associated with the only known chloromethane utilization pathway “ cmu ” in the microbial phyllosphere of the investigated ferns. Our study suggests that still unknown CH 3 Cl biodegradation processes on plants play an important role in global cycling of atmospheric CH 3 Cl. [ABSTRACT FROM AUTHOR]

This article 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. [ABSTRACT FROM AUTHOR]

Chloromethane (CH 3 Cl) and dichloromethane (CH 2 Cl 2 ) are known to have both natural and anthropogenic sources to the atmosphere. From recent studies it is known that tropical and sub tropical plants are primary sources of CH 3 Cl in the atmosphere. In order to quantify the biogenic emissions of CH 3 Cl and CH 2 Cl 2 from mangroves, field measurement were conducted in a tropical mangrove forest on the coast of Brazil. To the best of our knowledge these field measurements were the first of its kind conducted in the tropical mangrove ecosystem of Braganca. A mesoscale atmospheric model, MEsoscale TRAnsport and fluid (Stream) model (METRAS), was used to simulate passive tracers concentrations and to study the dependency of concentrations on type of emission function and meteorology. Model simulated concentrations were normalized using the observed field data. With the help of the mesoscale model results and the observed data the mangrove emissions were estimated at the local scale. By using this bottom-up approach the global emissions of CH 3 Cl and CH 2 Cl 2 from mangroves were quantified. The emission range obtained with different emission functions and different meteorology are 4–7 Gg yr −1 for CH 3 Cl and 1–2 Gg yr 2 for CH 2 Cl 2 . Based on the present study the mangroves contribute 0.3 percent of CH 2 Cl 2 and 0.2 percent of CH 3 Cl in the global emission budget. This study corroborates the study by Manley et al. (2007) which estimated that mangroves produce 0.3 percent of CH 3 Cl in the global emission budget. Although they contribute a small percentage in the global budget, their long lifetime enables them to contribute to the destruction of ozone in the stratosphere. From the detailed analyses of the model results it can be concluded that meteorology has a larger influence on the variability of concentrations than the temporal variability of the emission function. [ABSTRACT FROM AUTHOR]

Bacterial adaptation to growth with toxic halogenated chemicals was explored in the context of methylotrophic metabolism of Methylobacterium extorquens, by comparing strains CM4 and DM4, which show robust growth with chloromethane and dichloromethane, respectively. Dehalogenation of chlorinated methanes initiates growth-supporting degradation, with intracellular release of protons and chloride ions in both cases. The core, variable and strain-specific genomes of strains CM4 and DM4 were defined by comparison with genomes of non-dechlorinating strains. In terms of gene content, adaptation toward dehalogenation appears limited, strains CM4 and DM4 sharing between 75 and 85% of their genome with other strains of M. extorquens. Transcript abundance in cultures of strain CM4 grown with chloromethane and of strain DM4 grown with dichloromethane was compared to growth with methanol as a reference C1 growth substrate. Previously identified strain-specific dehalogenase-encoding genes were the most transcribed with chlorinated methanes, alongside other genes encoded by genomic islands (GEIs) and plasmids involved in growth with chlorinated compounds as carbon and energy source. None of the 163 genes shared by strains CM4 and DM4 but not by other strains of M. extorquens showed higher transcript abundance in cells grown with chlorinated methanes. Among the several thousand genes of the M. extorquens core genome, 12 genes were only differentially abundant in either strain CM4 or strain DM4. Of these, 2 genes of known function were detected, for the membrane-bound proton translocating pyrophosphatase HppA and the housekeeping molecular chaperone protein DegP. This indicates that the adaptive response common to chloromethane and dichloromethane is limited at the transcriptional level, and involves aspects of the general stress response as well as of a dehalogenation-specific response to intracellular hydrochloric acid production. Core genes only differentially abundant in either strain CM4 or strain DM4 total 13 and 58 CDS, respectively. Taken together, the obtained results suggest different transcriptional responses of chloromethane- and dichloromethane-degrading M. extorquens strains to dehalogenative metabolism, and substrate- and pathway-specific modes of growth optimization with chlorinated methanes.

A reactor setup consisting of two stainless steel microreactors [gas-phase microreactor (GPMR)-mix from the Institut für Mikrotechnik Mainz (IMM)] coupled in series was used for production of methyl chloride by hydrochlorination of methanol. The catalyst was γ-alumina on microreactor platelets. The influence of temperature on the methanol conversion and methyl chloride selectivity was investigated. A maximum conversion of 97.6% and a selectivity of 98.8% were reached at 340°C, which is close to the calculated thermodynamic equilibrium. Comparison with results obtained from a single microreactor and the modified setup of two microreactors revealed that the serial coupling resulted in a dead volume with a blind activity, which cannot be neglected when describing the setup. Furthermore, the separation of methyl chloride using condensers was investigated. The proposed microreactor-condenser concept enables the production of methyl chloride with a high purity.

Bacterial adaptation to growth with toxic halogenated chemicals was explored in the context of methylotrophic metabolism of Methylobacterium extorquens, by comparing strains CM4 and DM4, which show robust growth with chloromethane and dichloromethane, respectively. Dehalogenation of chlorinated methanes initiates growth-supporting degradation, with intracellular release of protons and chloride ions in both cases. The core, variable and strain-specific genomes of strains CM4 and DM4 were defined by comparison with genomes of non-dechlorinating strains. In terms of gene content, adaptation toward dehalogenation appears limited, strains CM4 and DM4 sharing between 75 and 85% of their genome with other strains of M. extorquens. Transcript abundance in cultures of strain CM4 grown with chloromethane and of strain DM4 grown with dichloromethane was compared to growth with methanol as a reference C1 growth substrate. Previously identified strain-specific dehalogenase-encoding genes were the most transcribed with chlorinated methanes, alongside other genes encoded by genomic islands (GEIs) and plasmids involved in growth with chlorinated compounds as carbon and energy source. None of the 163 genes shared by strains CM4 and DM4 but not by other strains of M. extorquens showed higher transcript abundance in cells grown with chlorinated methanes. Among the several thousand genes of the M. extorquens core genome, 12 genes were only differentially abundant in either strain CM4 or strain DM4. Of these, 2 genes of known function were detected, for the membrane-bound proton translocating pyrophosphatase HppA and the housekeeping molecular chaperone protein DegP. This indicates that the adaptive response common to chloromethane and dichloromethane is limited at the transcriptional level, and involves aspects of the general stress response as well as of a dehalogenation-specific response to intracellular hydrochloric acid production. Core genes only differentially abundant in either strain CM4 or strain DM4 total 13 and 58 CDS, respectively. Taken together, the obtained results suggest different transcriptional responses of chloromethane and dichloromethane-degrading M. extorquens strains to dehalogenative metabolism and substrate and pathway-specific modes of growth optimization with chlorinated methanes. [ABSTRACT FROM AUTHOR]

Flame propagation in a closed tube over mixtures of chloromethane and chlorine of different compositions following ignition by continuous UV radiation is studied. It is found that the rate of combustion in all mixtures except limiting ones grows along with the propagation of the flame front up to its maximum values at nearly 1/3 the tube length and then slows. In limiting mixtures, the speed's behavior is completely different. It is greatest near the source of UV light and gradually slows with distance from the source. The high speed in the initial section is due to the effect of UV light. The temperature of combustion is lowest in limiting mixtures, and the rate of chlorine molecule photodissociation at this temperature is comparable to and even faster than that of their thermal dissociation. The light in these mixtures thus contributes substantially to the initiation of the chemical reaction. It is concluded that when limiting mixtures are ignited by UV pulses, the speed of flame propagation falls markedly as it proceeds without the influence of radiation, and the character of changes in the speed's behavior becomes identical to those for other mixtures. [ABSTRACT FROM AUTHOR]

Halocarbons play an important role in combustion and stratospheric chemistry and have been an active subject of many studies for a long time. The six reaction channels, between CH 3 Cl and CN, have been investigated at CCSD(T)/aug-cc-pVTZ//CASSCF(11,10)/6-311++g(2df,p) level of theory. Only two channels dominate noticeably in the temperature range of 298–1000 K. The calculated values of the rate constants to different temperatures are in good agreement with the available experiment data. This reaction has a rate constant of k = 3.50 × 10−10 T − 0. 5 exp(−7.50 kJ mol−1/RT) over the range 298–1000 K. [Display omitted] • CCSD(T)//CASSCF(11,10) studies on the reaction kinetics of CN radical with chloromethane. • PESs for six reaction channels are evaluated at CASSCF(11,10)/6-311++g(2df,p) high level of theory. • Two channels dominate noticeably in the temperature range of 298–1000 K. • The MESMER package has been employed to evaluate the theoretical rate coefficients. [ABSTRACT FROM AUTHOR]

The introduction of small amounts of oxygen inhibits the photoinduced ignition of chloromethane-chlorine mixtures. This is accompanied by an increase in the induction period and a decrease in the degree of heating of the reaction mixture. After the consumption of the entire inhibitor, the photochlorination reaction takes place again in the thermal explosion regime but with a lower degree of heating. In the dependence of the mixture temperature on the oxygen concentration, criticality is not pronounced. With an increasing concentration of oxygen, its effect on the induction period weakens. [ABSTRACT FROM AUTHOR]