Dibromomethane Research Articles

Dibromomethane Knitted Highly Porous Hyper-Cross-Linked Polymers for Efficient High-Pressure Methane Storage.

Hyper-cross-linked polymers (HCPs) with ultra-high porosity, superior physicochemical stability, and excellent cost-effectiveness are attractive candidates for methane storage. However, the construction of HCPs with BET surface areas exceeding 3000 m2 g-1 remains extremely challenging. In this work, a newly developed DBM-knitting method with a slow-knitting rate is employed to increase the cross-linking degree, in which dichloromethane (DCM) is replaced by dibromomethane (DBM) as both solvent and electrophilic cross-linker, resulting in highly porous and physicochemically stable HCPs. The BET surface areas of DBM-knitted SHCPs-Br are 44%-120% higher than that of DCM-knitted SHCPs-Cl using the same building blocks. Remarkably, SHCP-3-Br exhibits an unprecedentedly high porosity (SBET = 3120m2g-1) among reported HCPs, and shows a competitive volumetric 5-100bar working methane capacity of 191 cm3 (STP) cm-3 at 273K calculated by using real packing density, which outperforms sate-of-art metal-organic framework (MOFs) at comparable conditions. This facile and versatile low-knitting-rate strategy enables effective improvement in the porosity of HCPs for porosity-desired applications.

Electron Donation from Boron Suboxides via Strong p-d Orbital Hybridization Boosts Molecular O2 Activation on Ru/TiO2 for Low-Temperature Dibromomethane Oxidation.

Low-temperature catalytic oxidation is of significance to the degradation of halogenated volatile organic compounds (HVOCs) to avoid hazardous byproducts with low energy consumption. Efficient molecular oxygen (O2) activation is pivotal to it but usually limited by the insufficient electron cloud density at the metal center. Herein, Ru-B catalysts with enhanced electron density around Ru were designed to achieve efficient O2 activation, realizing dibromomethane (DBM) degradation T90 at 182 °C on RuB1/TiO2 (about 30 °C lower than pristine Ru/TiO2) with a TOFRu value of 0.055 s-1 (over 8 times that of Ru/TiO2). Compared to the limited electron transfer (0.02 e) on pristine Ru/TiO2, the Ru center gained sufficient negative charges (0.31 e) from BOx via strong p-d orbital hybridization. The Ru-B site then acted as the electron donor complexing with the 2π* antibonding orbital of O2 to realize the O2 dissociative activation. The reactive oxygen species formed thereby could initiate a fast conversion and oxidation of formate intermediates, thus eventually boosting the low-temperature catalytic activity. Furthermore, we found that the Ru-B sites for O2 activation have adaptation for pollutant removal and multiple metal availability. Our study shed light on robust O2 activation catalyst design based on electron density adjustment by boron.

CsPbBr3 Perovskite Nanocrystals for Photocatalytic [3+2] Cycloaddition.

Visible-light-induced halide-exchange between halide perovskite and organohalide solvents has been studied in which photoinduced electron transfer from CsPbBr3 nanocrystals (NCs) to dihalomethane solvent molecules produces halide anions via reductive dissociation, followed by a spontaneous anion-exchange. Photogenerated holes in this process are less focused. Here, for CsPbBr3 in dibromomethane (DBM), we discover that Br radical (Br⋅) is a key intermediate resulting from the hole oxidation. We successfully trapped Br⋅ with reported methods and found that Br⋅ is continuously generated in DBM under visible light irradiation, hence imperative for catalytic reaction design. Continuous Br⋅ formation within this halide-exchange process is active for photocatalytic [3+2] cycloaddition for vinylcyclopentane synthesis, a privileged scaffold in medicinal chemistry, with good yield and rationalized diastereoselectivity. The NC photocatalyst is highly recyclable due to Br-based self-healing, leading to a particularly economic and neat heterogeneous reaction where the solvent DBM also acts as a co-catalyst in perovskite photocatalysis. Halide perovskites, notable for efficient solar energy conversion, are demonstrated as exceptional photocatalysts for Br radical-mediated [3+2] cycloaddition. We envisage such perovskite-induced Br radical strategy may serve as a powerful chemical tool for developing valuable halogen radical-involved reactions.

Mechano-chemical solution process for Li3PS4 solid electrolyte using dibromomethane for enhanced conductivity and cyclability in all-solid-state batteries

Increasing conductivity and stability is one of the essential and ultimate goals for electrolyte research. For sulfide solid-state electrolytes (SSEs), elemental doping is often suggested for this purpose. A typical doping method for sulfide SSE is an energy intensive and non-uniform solid-state reaction, because most solvents react with sulfide SSEs. Here, we have demonstrated that highly efficient Br-doping into lithium thiophosphate Li3PS4 (LPS) can be achieved through a solution-based strategy using dibromomethane (DBM) as Br-source and solvent in a ball-milling process. In this “mechano-chemical” process, simultaneous pulverization of large LPS particles and Br-doping occur, achieving remarkably improved Li+ ion conductivity (1.3 mS cm−1) which is eight times higher than that of the pristine LPS at only 1.14 at. % Br doping. This conductivity is one of the highest for LPS SSE, especially at this low doping level. The LPS to DBM ratio critically affects the efficiency of these chemical and physical modifications. In all-solid-state lithium-metal-batteries, the modified LPS exhibited exceptional cycling stability with reduced overpotential. The Li-Li symmetric cell demonstrated extremely stable Li deposition and stripping for over 1350 h, and the full cell with the Li anode and Li[Ni0.8Co0.1Mn0.1]O2 cathode retained 83 % of its initial capacity after 100 cycles. With possible application toward the slurry fabrication of LPS SSEs, the proposed approach provides a new and effective strategy for fabricating high-performance sulfide SSEs for large-scale applications.

Photooxidative Coupling of Thiols Promoted by Bromo(trichloro)methane in a Basic Aqueous Medium

AbstractA transition-metal- and organic-solvent-free oxidative coupling of thiols catalyzed by BrCCl3 and NaOH in an aqueous medium with oxygen as a green oxidant was established The facile and green method has a broad substrate scope in converting thiols into the corresponding disulfides with medium to excellent yields (up to 91%). This method could potentially be used to construct bioactive molecules containing disulfide bonds and to label bioactive molecules with disulfide bonds.

The use of the Roben Jig for preparation of clean coal samples of Western Canadian coals via density separation

ABSTRACT This study compared a water-based and a solvent-based method for removing ash (washing) from coal: jigging coal in water using the Roben Jig and the float/sink method using conventional organic liquids (naphtha, perchloroethylene, methylene bromide), respectively. Clean coal curves from the two processes were compared for six coal types from British Columbia, Canada. The clean coal curve for the Roben Jig deviated from that of the organic liquids when the near-density material content was high. Also, particles were misplaced within the jigging column; however, a simple “rejig” process was capable of further cleaning the coal. The Roben Jig was used to create a clean coal sample of at least 400 kg by washing coal in batches. The clean coal curves for the jig were similar. Minor differences could be attributed to the occurrence of misplaced particles. Although the Roben Jig does not provide perfect separation of coal based on density for use in wash plant design studies, previous work has established that it is capable of creating representative clean coal composites without the use of organic liquids.

Effect of elevated atmospheric CO2 concentration and temperature on volatile halogenated organic compound content in soils of Schima superba and Cunninghamia lanceolata seedlings.

Global changes caused by the increases of atmospheric CO2 concentration and temperature have important effects on soil biogeochemical processes. The synthesis and release of volatile halogenated organic compounds (VOXs) is an important pathway for soil to participate in the global material cycle and energy flow. In this study, Schima superba and Cunninghamia lanceolata seedlings in the southern subtropics were selected as the research objects. Four treatments, including control (CK), elevated CO2 concentration (EC), elevated temperature (ET) and elevated both factors (EC+ET) were set up. The effects of EC and ET on soil VOXs formation were studied by an open-top chamber system coupled with a purging and trapping gas chromatography/mass spectrometry. The results showed that VOXs content in the soil of S. superba seedlings was 0.065-0.252 ng·g-1, which was higher than that of C. lanceolata (0.038-0.136 ng·g-1). At the EC, ET and EC+ET treatments, VOXs contents were reduced in soils of both species. The effect of ET was the most significant, with the decrease rates of 74.2% and 72.1% in both soils, respectively. The change of VOXs content with increasing temperature mainly attributed to the changes of soil moisture and nitrogen content. The content of VOXs in the soils of S. superba seedlings decreased more than that of C. lanceolata under different treatments. In CK, EC, ET and EC+ET treatment, bromodichloromethane (BDCM) (27.5%, 36.7%, 32.9%, 32.6%) and tetrachloromethane (TCM) (9.0%, 16.8%, 22.7%, 15.8%) were the main VOXs in the soil of S. superba seedlings, respectively, while BDCM and dibromomethane (DBM) were the main VOXs in the soil of C. lanceolata seedlings. BDCM accounted for 31.9%, 38.2%, 40.9% and 37.2% of the VOXs content in each treatment, and DBM accounted for 17.9%, 16.5%, 19.2% and 16.0% of the VOXs content, respectively. Simulating elevated atmospheric CO2 concentration and temperature was conducive to more comprehensive reflection of the ecological effect of global climate change, and it could provide data support for improving the VOCs flux model.

Эмиссионные спектры жидкоструйных мишеней гексана C-=SUB=-6-=/SUB=-Н-=SUB=-14-=/SUB=-, дихлорметана CH-=SUB=-2-=/SUB=-Cl-=SUB=-2-=/SUB=-, бромистого метилена CH-=SUB=-3-=/SUB=-Br в диапазоне 4-20 nm при импульсном лазерном возбуждении

The article discusses the results of studying the emission spectra of liquid hexane C6H14, dichloromethane CH2Cl2, methylene bromide CH3Br upon excitation by pulsed laser radiation. We used a Nd:YAG laser, λ = 1064 nm, τ = 5 ns, Epulse = 0.8 J. The spectral range of 4–20 nm was studied. We used injector with a hole 225 μm in diameter, operating in a pulsed mode to form a liquid-droplet jet. The emission spectra of these liquid-jet targets were obtained. The obtained spectra were decoded, and the ions emitting in this spectral range were determined

Emission spectra of liquid-jet targets of hexane C-=SUB=-6-=/SUB=-H-=SUB=-14-=/SUB=-, dichloromethane CH-=SUB=-2-=/SUB=-Cl-=SUB=-2-=/SUB=-, methylene bromide CH-=SUB=-3-=/SUB=-Br in the range 4-20 nm under pulsed laser excitation

The article discusses the results of studying the emission spectra of liquid hexane C6H14, dichloromethane CH2Cl2, methylene bromide CH3Br upon excitation by pulsed laser radiation. We used a Nd : YAG,laser, λ=1064 nm, tau=5.2 ns, Epulse=0.8 J. The spectral range of 4-20 nm was studied. We used injector with a hole 225 μm ?m in diameter, operating in a pulsed mode to form a liquid-droplet jet. The emission spectra of these liquid-jet targets were obtained. The obtained spectra were decoded, and the ions emitting in this spectral range were determined Keywords: extreme ultraviolet radiation, emission spectra, laser spark, x-ray spectrometer-monochromator, liquid jets.

A generic gas chromatography method for determination of residual solvents in PET radiopharmaceuticals

A novel gas chromatography (GC) method for quantitation of volatile organic compounds (VOCs) in 18F- and 11C-radiopharmaceuticals listed in the European Pharmacopoeia (Ph. Eur.) was proposed. Optimized chromatographic parameters were used for separation of ethanol, acetone, acetonitrile, tetrahydrofuran (THF), dibromomethane (DBM), 2-dimethylaminoethanol (deanol), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) which could be detected in radioactive drug samples. The calculated peak resolutions (RS) were higher than 2.0 at ethanol concentration of up to 11 m/m%. Reproducible results could be obtained using base deactivated fused silica wool as packing material of inlet liner. Validation parameters showed excellent linearity (r2 ≥0.9998) in the range from 10 to at least 120% of concentration limit of solvents. The accuracy was determined as recovery of concentrations which ranged from 99.3% to 103.8%. Additionally, the relative standard deviation (RSD) of each solvent for inter-day and intra-day precision were in the range of 0.5–4.2% and 0.4–4.4%, respectively. The limit of quantitation (LOQ) for ethanol, acetone, acetonitrile, THF, DBM, deanol, DMF and DMSO was 0.48, 0.42, 0.43, 0.46, 4.35, 0.73, 0.68 and 0.50 mg/L, respectively. The developed procedure was successively applied for quantitation of ethanol, acetone, acetonitrile and deanol in radioactive drug samples of [11C]methionine, [11C]choline, 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) and O-(2-[18F]fluoroethyl)-L-tyrosine ([18F]FET). The proposed GC method applying flame ionization detection (FID) could be adapted in routine quality control of most frequently used positron emission tomography (PET) radiopharmaceuticals to perform the determination of residual solvents with analysis time of 12 min

Clariant launches catalyst R&D in Shanghai

This study compared three methods of removing mineral matter (washing) from coal: jigging coal particles in water using the Roben Jig, the float/sink method using traditional organic liquids (naptha, perchloroethylene, methylene bromide), and a full-sized industrial wash plant. Clean coal composites from six coal types (A, B, C, D, E, and F) were tested. All coals were washed using the Roben Jig and the float/sink method and seams E and F were also washed in an industrial wash plant. In each case, the Roben Jig was capable of producing a clean coal composites with coal quality characteristics (proximate analysis, FSI, S, calorific value, mineral analysis of ash, RoMax) very similar to that of the clean coal samples created by the organic liquids float/sink method and the industrial wash plant sample. The Gieseler fluidity and Ruhr dilatation values were lower in the traditional float/sink method where the coal was exposed to organic liquids. There was very little difference in the Sapozhnikov Y values and small differences in the G Caking Index values. All six coal types were carbonized in a sole-heated oven and CSR was tested. Comparing the CSRs for the clean samples created by the Roben Jig and organic liquids for coals A, B, C, and D, in four out of five cases the CSR from the organic liquids treated samples was higher (differences ranging from 2 to 8 points). Coals E and F were washed using all three methods and the samples prepared in the organic liquids had the highest CSRs (differences ranging from 3 to 7). The clean coal samples from Coal F were carbonized in a moveable wall oven. CSRs ranged from 66.7 to 69.2, with the plant sample having the highest value. ASTM stability values ranged from 51.7 to 57.3 with the lowest value resulting from the organic liquids washed sample.

Preparation of clean coal samples using the Roben Jig

This study compared three methods of removing mineral matter (washing) from coal: jigging coal particles in water using the Roben Jig, the float/sink method using traditional organic liquids (naptha, perchloroethylene, methylene bromide), and a full-sized industrial wash plant. Clean coal composites from six coal types (A, B, C, D, E, and F) were tested. All coals were washed using the Roben Jig and the float/sink method and seams E and F were also washed in an industrial wash plant. In each case, the Roben Jig was capable of producing a clean coal composites with coal quality characteristics (proximate analysis, FSI, S, calorific value, mineral analysis of ash, RoMax) very similar to that of the clean coal samples created by the organic liquids float/sink method and the industrial wash plant sample. The Gieseler fluidity and Ruhr dilatation values were lower in the traditional float/sink method where the coal was exposed to organic liquids. There was very little difference in the Sapozhnikov Y values and small differences in the G Caking Index values. All six coal types were carbonized in a sole-heated oven and CSR was tested. Comparing the CSRs for the clean samples created by the Roben Jig and organic liquids for coals A, B, C, and D, in four out of five cases the CSR from the organic liquids treated samples was higher (differences ranging from 2 to 8 points). Coals E and F were washed using all three methods and the samples prepared in the organic liquids had the highest CSRs (differences ranging from 3 to 7). The clean coal samples from Coal F were carbonized in a moveable wall oven. CSRs ranged from 66.7 to 69.2, with the plant sample having the highest value. ASTM stability values ranged from 51.7 to 57.3 with the lowest value resulting from the organic liquids washed sample.

Settlement and culture of post-larvae, spat and juveniles of the West Indian topshell, Cittarium pica (Linne, 1758)

The settlement, survival and growth rates of C. pica post-larvae, spat and juveniles were evaluated under different culture conditions. The factorial effect of six stimuli (low temperature, γ-aminobutyric acid, potassium chloride, hydrogen peroxide, dibromo methane, and coralline algae extract), five types of biofilm substrates (artificial, artificial with coralline algae, artificial with congener mucus, benthic microalgae, and microalgae with congeners mucus) and five stimulation times (6, 12, 24, 36 and 72 h) on the larval settlement of the topshell were assessed. In addition, growth and survival rates of post-larvae fed with artificial biofilm and benthic microalgae were compared. Similarly, growth and survival rates were assessed in spat cultured in different environments (outdoor and indoor), and juveniles grown in concrete tanks with different finished of the inner walls (gray rough finish, and white smooth walls with epoxy paint). A higher larval settlement was observed in substrates with artificial biofilm exposed to cold water (20 °C) for 24 h. Treatments with the stimulus of KCl and dibromo methane had toxic effects on larvae. There were not differences in the shell length of the settled larvae between stimuli, substrata or exposition time. Post-larvae fed with artificial biofilm had survival and growth rates similar to those maintained with benthic microalgae biofilm. The spat that were cultured in outdoor conditions showed a higher growth rate than those kept indoor, but the survival was similar in both cases. Finally, juveniles grown in tanks with rough, gray concrete inner walls had higher growth and survival rates, compared to those held in tanks with smooth white finish. The improvements obtained in growth and survival of post-larvae, spat and juveniles of C. pica suggest that there is a great biological potential for its wild populations restocking and for its aquaculture in sea-based systems.

Dibromomethane as Promising Gaseous Fire Extinguishing Substance with Short Atmospheric Lifetime

Calculation of dibromomethane atmospheric lifetime is carried out, as well as an experimental assessment of its fire extinguishing efficiency. Calculations show that methylene bromide atmospheric lifetime is 15.8 days so it rapidly decomposes in the troposphere. The main mechanisms of the removal of CH2Br2 from the atmosphere are its reaction with hydroxyl radicals and the processes of physical removal from the atmosphere. Special experimental equipment allowing to measure fire extinguishing concentration of gaseous fire suppressant having high boiling point is described. Experimentally measured minimum extinguishing concentration of methylene bromide for n-heptane is 2.5 % vol. According to this, CH2Br2 is close to the most effective gaseous fire extinguishing agents, such as C3F7I and C2F4Br2. LOAEL value for CH2Br2 is predicted at the level of 0.3-0.4 % vol. Due to the high boiling point of methylene bromide and its relatively high toxicity, the most appropriate way to use it in fire suppression is to create fire extinguishing mixtures, in particular, with fluorinated hydrocarbons. This approach allows to diminish application of greenhouse gases in fire protection and also to solve the problem of toxicity of extinguishing substance.

컨테이너 하역 작업자의 유해화학물질 노출 위험도 분석

Containers usually are used as the general oversea transportation facilities in global. The fumigation materials such as Methyl bromides and formaldehyde, which would be known to be toxic to human or anima beings, commonly are used to remove harmful insect inner containers. Also, workers in unloading container would be easily exposed to toxic materials at working sites and have been reported to occur the safety accidents which would cause many health and damages of workers. In this study, the experimental analysis would be conducted for container unloading workers

Synthesis and characterization of some novel coumarin based various 2-aryl-pyrido [3,2-c] coumarins

A survey of the literature reveals that the number of coumarin derivatives having heterocyclic moieties either as substituent groups or fused with parent coumarin nucleus possesses a variety of functions and are widely used in drugs and dyes. Because of this wide utility, the synthesis of coumarin has remained a subject of active interest. Looking at the importance of these heterocoumarins and with a view to exploring new methods of their synthesis, the present work was undertaken and this synthesis deals with various 2-aryl-pyrido [3,2-c] coumarins. The compounds have been synthesized by reacting Mannich bases of various 4-hydroxy coumarins with pyridinium salts of various aroyl methyl bromides in the presence of ammonium acetate and acetic acid. All the compounds synthesized have been characterized by analytical and spectral data.
 Keywords: Pyrido, Coumarins, Krohanke’s reaction.

Total Trihalomethane Levels in Major Watersheds across the United States

Trihalomethanes, such as chloroform, bromoform, dibromo(chloro)methane, and bromo(dichloro)methane, are present in the major watersheds across the United States. These chemicals play an important role in the development of cancer, have adverse reproductive outcomes, and were found to be present above the threshold established by the Environmental Protection Agency. To understand the impact of socioeconomic background on the quality of water and possible disparities, we have analyzed the levels of total trihalomethanes in the metropolitan areas in the major watersheds across the United States, in 2018, as they correlated to average household incomes. Our study found that Arkansas, Nevada, and Rhode Island demonstrated higher than federally mandated levels of total trihalomethanes in their watersheds. The median annual household and per capita incomes of the three states (Arkansas, Nevada, and Rhode Island) were lower than the national average. In addition, Delaware, New Hampshire, and Wisconsin, which had higher median income levels, demonstrated the lowest total trihalomethane levels across the United States.

Thermodynamic study of mixtures containing dibromomethane. II: volumes and enthalpies at 298.15 K

Excess molar volumes, VE, of binary mixtures of dibromomethane (DBM) with n-hexane, n-heptane, n-octane, cyclohexane, tetrachloromethane, dipropyl and dibutyl ether, tetrahydrofuran, and 3-pentanone are determined at 298.15 K in the whole composition range by means of a vibrating tube densimeter. For the same DBM mixtures plus with n-pentane and except with dipropyl ether and 3-pentanone, partial molar enthalpies, Hi, and excess molar enthalpies, HE, are obtained through a heat flow calorimeter and a titration method purposely devised. Both excess properties are positive for cyclohexane, tetrachloromethane, and n-alkanes, the latter exhibiting an increase with increasing number of carbon atoms. Dipropyl and dibutyl ether mixtures exhibit negative VE values, while n-hexane, tetrahydrofuran, and 3-pentanone mixtures show an S-shaped VE curve. Negative HEs are observed only for tetrahydrofuran, whereas dibutyl ether exhibits an S-shaped HE curve. HE results are compared with the predictions of the DISQUAC model. The partial molar volumes at infinite dilution, V°, as well as the enthalpies of solvation, ΔsolvH°, of the examined substances in DBM are evaluated and discussed also considering data on other compounds found in the literature. For V° and ΔsolvH°, a group additivity scheme is proposed to enable the estimation of these properties for other molecules and how much structural peculiarities such as chain length, polarity of groups, and cyclic structures influence their values.

Leaching of Organic Toxic Compounds from PVC Water Pipes in Medina Al-Munawarah, Kingdom of Saudi Arabia

It is well established that the use of synthetic material in water pipes significantly affects the quality of domestic water, especially trace organics that are leached through with the flow of water. In the present study, the migration of volatile organic compounds (VOCs) from water pipes manufactured of polyvinyl chloride (PVC) has been investigated using static laboratory conditions and in residential areas. The contact of deionized water with various PVC pipes for three successive test periods of 24, 48, and 72 h duration has been made. Twenty water samples were collected from houses within Medina Al-Munawarah residential area and were analyzed by using solid phase extraction, followed by high resolution gas chromatography with flame ionized detector (GC-FID). The presence of carbon tetrachloride (CTC), toluene, chloroform, styrene, o-xylene, bromoform (BF), dibromomethane (DBM), cis-1,3-dichloropropane (Cis-1,3-DCP), and trans-1,3-dichloropropane (Trans-1,3-DCP) was initially confirmed. The most frequent contaminants found were DBM, CTC, and toluene that were monitored in 55%, 50%, and 45% of samples, respectively. The levels of CTC, Cis-1,3-DCP, and Trans-1,3-DCP were found to exceed the World Health Organization (WHO) limits in 50%, 20%, and 20% of samples, respectively. The migration test indicated that nine of the targeted contaminants occur in a double distilled water sample incubated in pipe in laboratory level experiment. This implies that these components are more likely to migrate from PVC pipe in home plumbing systems network.

Effect of dihalides on the polymer linkages in the Cs2CO3-promoted polycondensation of 1 atm carbon dioxide and diols

Synthesis of biodegradable polycarbonates directly from carbon dioxide and diols has seen renewed interest. In the present report, the effect of a series of organic dihalides (CH2X2 and (CHX)2, where X = Cl, Br, and I) in the Cs2CO3-promoted copolymerization of 1 atm CO2 with diols has been studied. Structural analysis of the resultant polymers/oligomers by spectroscopic techniques reveals that a variety of main chain linkages can be obtained, depending on the dihalides used. Specifically, the methylene units from dibromomethane (DBM) are incorporated into the products as carbonate and ether linkages, and the methylene units from diiodomethane (DIM) are incorporated mainly as the ether linkage and without much CO2 incorporation. In comparison, all dihaloethanes examined lead to clean formation of alternating polycarbonates incorporating both the ethylene units from dihaloethanes and the diol units, and the halide is identified as the end group. The mechanistic pathways and the relative activity of the key intermediates are discussed in light of these results.