Mixture Of Dichloromethane Research Articles

Development of a Stability-Indicating Stereoselective Method for Quantification of the Enantiomer in the Drug Substance and Pharmaceutical Dosage Form of Rosuvastatin Calcium by an Enhanced Approach.

A novel, simple, precise, and stability-indicating stereoselective method was developed and validated for the accurate quantification of the enantiomer in the drug substance and pharmaceutical dosage forms of Rosuvastatin Calcium. The method is capable of quantifying the enantiomer in the presence of other related substances. The chromatographic separation was achieved with an immobilized cellulose stationary phase (Chiralpak IB) 250 mm x 4.6 mm x 5.0 μm particle size column with a mobile phase containing a mixture of n-hexane, dichloromethane, 2-propanol, and trifluoroacetic acid in the ratio 82:10:8:0.2 (v/v/v/v). The eluted compounds were monitored at 243 nm and the run time was 18 min. Multivariate analysis and statistical tools were used to develop this highly robust method in a short span of time. The stability-indicating power of the method was established by subjecting Rosuvastatin Calcium to the stress conditions (forced degradation) of acid, base, oxidative, thermal, humidity, and photolytic degradation. Major degradation products were identified and found to be well-resolved from the enantiomer peak, proving the stability-indicating power of the method. The developed method was validated as per International Conference on Harmonization (ICH) guidelines with respect to specificity, limit of detection and limit of quantification, precision, linearity, accuracy, and robustness. The method exhibited consistent, high-quality recoveries (100 ± 10%) with a high precision for the enantiomer. Linear regression analysis revealed an excellent correlation between the peak responses and concentrations (r2 value of 0.9977) for the enantiomer. The method is sensitive enough to quantify the enantiomer above 0.04% and detect the enantiomer above 0.015% in Rosuvastatin Calcium. The stability tests were also performed on the drug substances as per ICH norms.

Formulation and evaluation of gastroretentive microballoons containing baclofen for a floating oral controlled drug delivery system.

The objective of the present study was to fabricate and evaluate a multiparticulate oral gastroretentive dosage form of baclofen characterized by a central large cavity (hollow core) promoting unmitigated floatation with practical applications to alleviate the signs and symptoms of spasticity and muscular rigidity. Solvent diffusion and evaporation procedure were applied to prepare floating microspheres with a central large cavity using various combinations of ethylcellulose (release retardant) and HPMC K4M (release modifier) dissolved in a mixture of dichloromethane and methanol (2:1). The obtained microspheres (700-1000 µm) exhibit excellent floating ability (86 ± 2.00%) and release characteristics with entrapment efficiency of 95.2 ± 0.32%. Microspheres fabricated with ethylcellulose to HPMC K4M in the ratio 8.5:1.5 released 98.67% of the entrapped drug in 12 h. Muscle relaxation caused by baclofen microspheres impairs the rotarod performance for more than 12 h. Abdominal X-ray images showed that the gastroretention period of the floating barium sulfate- labeled microspheres was no less than 10 h. The buoyant baclofen microspheres provide a promising gastroretentive drug delivery system to deliver baclofen in spastic patients with a sustained release rate.

Analysis of Contaminants Found from Soils in the Abandoned Railroad Sites

Recently, reconstruction of abandoned railroad stations and railroad beds are increasingly taking place in Korea. Soil remediation is necessary for the eco-friendly development. Soil found in abandoned railroad sites typically contaminated with heavy oils, which are low volatile petroleum products and less decomposable in nature. The objective of this study is to analyze those contaminants and contamination levels of the soils collected from an abandoned railroad bed located in Seoul, Korea. Heavy oils were extracted from contaminated soils using an organic solvent mixture of methanol and dichloromethane (1:2, v/v). Extracted solvent were analyzed qualitatively by Fourier transform infrared spectroscopy (FT-IR) and qualitatively using high performance liquid chromatography. It was found that the abandoned railroad bed soil was mainly contaminated by heavy oils such as bunker C oil, which was confirmed by FT-IR spectra of petroleum oil products such as gasoline, diesel, kerosene, JP-8, bunker C oil, and lubricants. Benzo [a] antracene was found from the contaminated soil and its level was as high as 11.45 mg/kg, and other polycyclic aromatic hydrocarbons were trivial.

Reversed Phase SPE and GC-MS Study of Polycyclic Aromatic Hydrocarbons in Water Samples from the River Buriganga, Bangladesh.

Polycyclic aromatic hydrocarbons (PAHs) are semivolatile organic compounds (SVOCs) categorized as persistent organic pollutants (POPs). PAHs are ubiquitous in terrestrial, atmospheric, and particularly aquatic environments throughout the world and have been detected in lakes, ground waters, and rivers. This research work involved the analysis of five PAHs, anthracene, fluorene, naphthalene, phenanthrene, and pyrene, in water sample collected from the river Buriganga, Bangladesh. The extraction of water samples was carried out by reversed phase solid-phase extraction (RP-SPE) technique with C-18 SPE cartridges. A solvent mixture of dichloromethane and hexane (1 : 2) with a flow rate of 0.5 mL/min was used as eluent. Percentage recoveries of five PAHs for this technique were in the range of 81.47 ± 1.16 to 98.60 ± 0.61%. PAHs quantification was achieved by using an ion trap gas chromatography mass spectrometer (GC-MS) interfaced to gas chromatography (GC) equipped with a fused silica capillary column. Helium was used as carrier gas with a flow rate of 1.0 mL/min. The commonly detected PAH compounds in the river water were anthracene, naphthalene, and phenanthrene at the concentration ranges of 0.451 to 3.201, 0.033 to 3.1131, and 0.320 to 2.546 μg/mL, respectively. The results reflect that PAHs presented in this river water were mostly from petrogenic and pyrogenic sources.

Wettability Improvement of Poly (Butylene Terephthalate) Nanofibrous Mats Prepared via Electrospinning by Blending With Regenerated Silk Fibroin

Poly (butylene terephthalate) (PBT)/regenerated silk fibroin (RSF) blend electrospun nanofibrous mats were manufactured to combine the excellent mechanical behavior of PBT with the extraordinary hydrophilic property of RSF. A 1:1 mixture of trifluoroacetic acid (TFA) and dichloromethane (DCM) was adopted as the solvents for PBT and RSF with 20% (w/v) PBT and 16 wt% RSF solutions being mixed in various proportions for electrospinning. The morphology, crystallization, Fourier transform infrared (FTIR) spectra, surface roughness, contact angle, and wetting time of the electrospun blended materials were studied. When the weight ratio of RSF was larger than 50%, a water drop on the surface of the electrospun mat was completely permeated within 300 s or less. Besides the chemical influence of the amino and carboxy groups in RSF, the physical characteristics of the RSF in the blend electrospun mats, such as random coil structure, lower crystallinity, rougher surface than PBT, etc., were a partial reason for the improvement of wettability. The blend nanofibrous mats may be especially applicable in biomedical fields.

EFFECT OF HYDROPHILIC POLYMER IN THE RELEASE PATTERN OF TERBUTALINE SULPHATE TRANSDERMAL PATCH

The aim of the study is to formulate matrix based transdermal patch for water soluble drug like terbutaline and to study the effect of formulation composition on physical property, to study permeation profile of the patches through hairless mice skin and to study release profile of the patches. Five monolayered terbutaline sulphate transdermal patches bearing a rate controlling membrane were prepared by solvent-casting technique. Five formulations were prepared with varying concentrations of sodium alginate- FI, FII, FIII, FIV and FV with 350mg, 450mg, 250mg, 400mg and 300mg respectively. The 15mg terbutaline sulphate, 0.5ml glycerine and 0.1% chlorocresol were used along with sodium alginate in preparation of drug matrix. A mixture of ethylcellulose, chloroform and dichloromethane were used for preparation of rate controlling membrane using dibutylphthalate as a plasticizer. The physicochemical characteristics of the patches were evaluated by standard techniques. In-vitro drug release test was done in Keshary Chein diffusion cell by using skin of albino mice for 6 hours study. From the in-vitro permeation release study, formulation FII, FIV and FV followed Higuchi order kinetics while FI followed Peppas equation and FIII followed first order kinetics. Formulation FII showed more permeability than other formulations due to high concentration of sodium alginate in the FII. Thus the release of drug was found to be directly related to the concentration of SA.

Tetra-nuclear copper complex having P–N–P ligand to P–O–P ligand – synthesis, structural, and mechanistic studies

We report the synthesis and structures of three copper(I) complexes, [Cu4(μ3-Cl)2(μ2-Cl)2{μ2-(2,6-Me2C6H3N(PPh2)2)}2] (2), [Cu4(μ3-Cl)2(μ2-Cl)2{μ2-(Ph2POPPh2)}2] (4), and [Cu2(μ2-Cl)2(μ2-PPh2OPPh2)(η1-Ph2PP(=O)Ph2)(PPh3)] (5), and one cobalt complex, [(CoCl2){μ2-2,6-Me2C6H3N(PPh2)2}2][CoCl3NH2(2,6-Me2Ph)] (3). Tetra-nuclear copper complex 2 was prepared in good yield by the reaction of bis(diphenylphosphino)-2,6-dimethylaniline [2,6-Me2C6H3N(PPh2)2] (1) with copper(I) chloride along with triphenylphosphine in methanol. Adding a calculated amount of water and dichloromethane mixture (1 : 10) to 2 produced a second tetra-nuclear copper(I) complex, 4, with a P–O–P backbone, along with a small amount of the unsymmetrical copper(I) complex 5. The cobalt complex 3 was obtained by reaction of 1 with cobalt(II) chloride. The solid-state structures of 2–5 were established by single-crystal X-ray diffraction analysis. In the solid state, both 2 and 4 form a tetra-nuclear copper core. In the 31P{1H} NMR study, we observed the conversion of 2, with P–N–P backbone, to 4, with P–O–P backbone.

Tuning of intermolecular interactions results in packing diversity in imidazolin-5-ones

Crystal structures of four green fluorescent protein (GFP) chromophore analogues with different packing interactions could be tuned by appropriate substitutions around the imidazolin-5-one ring are reported here. Compound 1 was crystallized from tetrahydrofuran at room temperature while compounds 2-4 have been crystallized from a mixture of methanol and dichloromethane in 3:1 ratio. Molecule 1, 2 and 3 crystallized in monoclinic lattice while molecule 4 preferred to crystallize in a triclinic crystal system. The crystal packing of these molecules was stabilized by C-H…π stacking and C-H… O type of supramolecular interactions. The results reveal that packing diversity can be easily accomplished in these molecules by tuning the substituents around the imidazolin-5-one ring. Photophysical studies also reveal that all have good quantum yield and fluoresce typically in red region due to presence of electron donating groups around the imidazolin-5-one ring. Crystal structures of four green fluorescence protein (GFP) chromophore analogues are reported. Stabilization through packing and packing diversity in crystals are achieved by modulating supramolecular interaction by varying the substituents.

Adducts of Trimeric Perfluro-o-Phenylene Mercury with TTF or DTT

Since the discovery of metallic conductivity in the TTF-TCNQ complex, the charge transfer (CT) complex materials have been studied for such properties as semiconductivity or superconductivity. The synthesis of new CT materials using trimeric perfluoro-ortho-phenylene mercury (Hg3) as electron acceptor compound was done first by Haneline and Gabaï [1]. A series of studies of CT materials containing Hg3 and tetrathiafulvalene (TTF) or dithieno thiophene (DTT) as an electron donor compounds was carried out by different methods. Co-crystalzation with TTF gave a larger variety of co-crystals than with DTT, producing three polymorphs and one pseudo-polymorph. One pot crystal growth of TTF and Hg3 in a 1:1 mixture of solvents dichloromethane (DCM) and dichloroethane (DCA) has led to the formation of TTF polymorphs 1 and 2 with same 1:1 donor acceptor ratio [Hg3·TTF] as well a pseudopolymorph [Hg3·TTF·DCA] 3 that contains the solvent DCA in the asymmetric unit. Slow evaporation in a 1:1 mixture of dichloromethane and carbon disulfide was used to obtain the previously reported CT [(Hg3)2·TTF] (4)1. By slow evaporation as well in pure dichloromethane was obtained the CT material [Hg3·DTT·DCM] 5. All these five CT co-crystals contain mixed donor acceptor stacks, however only in 3, 4 and 5 these stacks are parallel to each other. In the packing of 1 and 2 these stacks are in herringbone arrangement. Polymorphs 1 and 2 differ in crystal shape and color. Contacts Hg···S shorter than the sum of the Van Der Walls radii were observed in the five CTs materials reported, however only 1, 2, 3, and 5 have extended short donor acceptor molecular associates. Moreover only 3, and 5 has these extended donor acceptor associates along one direction.

Packing forces in dichloridobis(3,5-diphenyl-1H-pyrazole-κN(2))cobalt(II) dichloromethane hemisolvate.

The title compound, [CoCl2(C15H12N2)2]·0.5CH2Cl2, was crystallized from a binary mixture of dichloromethane and hexane and a dimeric supramolecular structure was isolated. The Co(II) centre exhibits a distorted tetrahedral geometry, with two independent pyrazole-based ligands occupying two coordination sites and two chloride ligands occupying the third and fourth coordination sites. The supramolecular structure is supported by complementary hydrogen bonding between the pyrazole NH group and the chloride ligand of an adjacent molecule. This hydrogen-bonding motif yields a ten-membered hydrogen-bonded ring. Density functional theory (DFT) simulations at the PBE/6-311G level of theory were used to probe the solid-state structure. These simulations suggest that the chelate undergoes a degree of conformational distortion from the lowest-energy geometry to allow for optimal hydrogen bonding in the solid state.

Phase Behavior of Poly(d-lactic acid), Dichloromethane, and Carbon Dioxide Ternary Mixture Systems at High Pressure

The phase behavior of a poly(d-lactic acid) (Mw = 359 000 g/mol, polydispersity 1.7), carbon dioxide, and dichloromethane ternary system was measured by a variable-volume view cell. The experimental temperatures and pressures ranged from 313.15 to 363.15 K, up to 300 bar as various experimental conditions of the CO2/dichloromethane mass ratio and temperature, at poly(d-lactic acid) mass fractions of 1.0, 2.0, and 3.0%. The correlation results were obtained from the hybrid equation of state (Peng–Robinson equation of state + SAFT equation of state) using the van der Waals one-fluid mixing rule for the polymer–CO2–solvent system. The binary interaction parameters were optimized by the simplex method algorithm.

Probing the potential of polyester for CO2 capture

Global warming, the major environmental issue confronted by humanity today, is caused by rising level of green house gases. Carbon capture and storage technologies offer potential for tapering CO2 emission in the atmosphere. Adsorption is believed to be a promising technology for CO2 capture. For this purpose, a polyester was synthesized by polycondensation of 1,3,5-benzenetricarbonyl trichloride and cyanuric acid in pyridine and dichloromethane mixture. The polymer was then characterized using FT-IR, TGA, BET surface area and pore size analysis, FESEM and CO2 adsorption measurements. The CO2 adsorption capacities of the polyester were evaluated at a pressure of 1bar and two different temperatures (273 and 298K). The performance of these materials to adsorb CO2 at atmospheric pressure was measured by optimum CO2 uptake of 0.244mmol/g at 273K. The synthesized polyester, therefore, has the potential to be exploited as CO2 adsorbent in pre-combustion capture process.

Characteristics and chemical compositions of propolis from Ethiopia

IntroductionPropolis is a sticky material mixed by honeybees to utilize it in protecting their hives from infection by bacteria and fungi. The therapeutic properties of propolis are due to its chemical composition with bio-active compounds; therefore, researchers are interested in studying its chemical constituents and biological properties. The main objective of this study is to determine the chemical compositions, characteristics and relative concentrations of organic compounds in the extractable organic matter of propolis samples collected from four different areas in Ethiopia.ResultsThe propolis samples were extracted with a mixture of dichloromethane and methanol and analyzed by gas chromatography–mass spectrometry (GC-MS).The results showed that the total extract yields ranged from 27.2% to 64.2% (46.7 ± 19.1%). The major compounds were triterpenoids (85.5 ± 15.0% of the total extracts, mainly α-, β-amyrins and amyryl acetates), n-alkanes (5.8 ± 7.5%), n-alkenes (6.2 ± 7.0%,), methyl n-alkanoates (0.4 ± 0.2%), and long chain wax esters (0.3 to 2.1%).ConclusionThe chemical compositions of these propolis samples indicate that they are potential sources of natural bio-active compounds for biological and pharmacological applications.

Characterization of Highly Oxygenated and Environmentally Weathered Crude Oils by Liquid Chromatography Fourier Transform Ion Cyclotron Mass Spectrometry (FT-ICR MS)

Heavy and biodegraded oils exhibit an ever increasing oxygen complexity. Electrospray ionization (ESI) coupled to FT-ICR MS highlights the most acidic and basic oxygen species; however, quantitative and qualitative information about less polar oxygenated compounds is essential to understand both the source and, potentially, the modification pathways for oxygenated crude oils. Liquid chromatography (LC) is complementary to FT-ICR MS to deconvolve crude oils according to oxygen functionality, thereby enriching oxygen species that are not easily ionized or are present in low abundance. Ketones and carboxylic acids dominate most environmentally modified crude oils; however, phenols and polyphenols are also important intermediates in both biotic and abiotic modifications. Moreover, due to the nature of the refinement process, oxygen-containing species and their intermediates can serve as chemical tracers in produced water streams and areas of rapid thermal changes that lead to gum or deposit formation. Here, we describe an analytical separation scheme for an environmentally weathered (highly oxygenated) crude oil designed to highlight carboxylic acid isolation and ketone enrichment, as well as the separation of other oxygen compounds by polarity. Experimental A weathered beach extract collected from the coast of Florida was fractionated by LC and analyzed by FT-ICR MS. LC techniques are designed to target specific oxygen functionalities (e.g., ketones, alcohols, phenols, and carboxylic acids). The mass spectra of the LC fractions were acquired with a custom-built 9.4 T FT-ICR Instrument. Positive and negative electrospray ionization serve to highlight basic and acidic oxygen species. Preliminary DataLC fractionation was performed with a silicic acid stationary phase. Four fractions correspond to aromatics, neutral nitrogen, basic nitrogen, and polar compounds. Positive ESI FT-ICR MS indicated a relative abundance for the O1 heteroatom class ranging from 2% in the whole beach extract to 12 % in the neutral nitrogen fraction. The increased relative abundance of O1 compounds suggests the enrichment of ketones from the original sample. Carboxylic acids are isolated by retention on an amine stationary phase and subsequent elution with a mixture of dichloromethane, methanol, and formic acid. Oxygen species will be further probed with new separation schemes to focus on analysis of phenols.

English

In this study, polycyclic aromatic hydrocarbons (PAHs) associated with airborne particulate pollutants of aerodynamic size 10 μm (PM10) were studied for three months, from October to December 2010 in the Vanderbijlpark area. Some PAHs are highly carcinogenic and could be more harmful when combined with inhalable PM10. A dual E-Sampler which combines the light scatter and the gravimetric filter methods was used. A 10 mg/L standard stock solution that contained naphthalene (Naph), 2-methyl naphthalene (2-MNaph), phenanthrene (Phe), anthracene (Anth), benzo(b)fluoranthene (BbFl), benzo(k)fluoranthene (BkFl), benzo(a)pyrene (BaPy) and dibenzo(a,h)anthracene (DiBahAn) was prepared, compounds were indentified and quantified with an Agilent high performance liquid chromatography (HPLC). A dichloromethane (DCM) and n-hexane (1:1) extraction mixture was used to extract the pollutants from both exposed and unexposed (blank) filters. Detection limits obtained ranged from 0.001 to 0.0305 mg/L and R-values ranged from 0.996 – 0.999. Very good percentage recoveries were obtained with the lowest 97.63% and highest 101.57% associated with DiBahFl and 2-MNaph, respectively. Total concentration of 2-MNaph obtained per month were 325.2 ng/L (October 2010), 162.4 ng/L (November 2010) and 381.2 ng/L (December 2010). Relatively high levels of 2-MNaph were detected consistently when compared with other pollutants in the three months. Concentration ranges of other PAH compounds were Anth (7.2 - 14.76 ng/L), BbFl (6.7 - 13.6 ng/L), BaPy (6.8 - 13.0 ng/L) and BkFl (6.7 - 10.8 ng/L). Daily and monthly mass concentration levels obtained were lower than the strict regional daily limit of 0.075 µg/m3, as well as national and international daily limits of 0.150 µg/m3. These results could be used as the basis for undertaking a comprehensive study on the status of these organic compounds from the heavily industrialized Vaal Triangle region. Key words: Polycyclic aromatic hydrocarbons (PAHs), PM10, distribution, concentration, high performance liquid chromatography (HPLC), Vanderbijlpark.

Degradation of dichloromethane by an isolated strain Pandoraea pnomenusa and its performance in a biotrickling filter

A strain Pandoraea pnomenusa LX-1 that uses dichloromethane (DCM) as sole carbon and energy source has been isolated and identified in our laboratory. The optimum aerobic biodegradation of DCM in batch culture was evaluated by response surface methodology. Maximum biodegradation (5.35 mg/(L·hr)) was achieved under cultivation at 32.8°C, pH 7.3, and 0.66% NaCl. The growth and biodegradation processes were well fitted by Haldane's kinetic model, yielding maximum specific growth and degradation rates of 0.133 hr−1 and 0.856 hr−1, respectively. The microorganism efficiently degraded a mixture of DCM and coexisting components (benzene, toluene and chlorobenzene). The carbon recovery (52.80%–94.59%) indicated that the targets were predominantly mineralized and incorporated into cell materials. Electron acceptors increased the DCM biodegradation rate in the following order: mixed > oxygen > iron > sulfate > nitrate. The highest dechlorination rate was 0.365 mg Cl−/(hr·mg biomass), obtained in the presence of mixed electron acceptors. Removal was achieved in a continuous biotrickling filter at 56%–85% efficiency, with a mineralization rate of 75.2%. Molecular biology techniques revealed the predominant strain as P. pnomenusa LX-1. These results clearly demonstrated the effectiveness of strain LX-1 in treating DCM-containing industrial effluents. As such, the strain is a strong candidate for remediation of DCM coexisting with other organic compounds.

Experimental designs characterizing seasonal variations and solvent effects on the quantities of coumarin and related metabolites from Mikania laevigata

Statistical design mixtures of acetone, chloroform, dichloromethane and ethanol were used to study the effects of different solvents and their mixtures on the quantities of coumarin and related metabolites extracted from Mikania laevigata samples harvested in each of the four seasons. RP-HPLC-DAD and both positive and negative modes of UPLC-MS analyses were used to determine relative quantities of coumarin, o-coumaric acid and melilotic acids in each season for all the mixture design extracts. The existence and measurement of the relative abundances of melilotic acid in Mikania laevigata have not been reported previously. Highest coumarin concentrations were encountered in the summer whereas its o-coumaric acid precursor and melilotic acid were most abundant in the spring. O-coumaric and melilotic acids concentrations were strongly correlated during the year. Also solvent effects were seen to be significant. Ethanol and 1:1 binary mixtures of ethanol and acetone extracted the largest quantities of coumarin whereas ethanolic binary and ternary mixtures with chloroform and dichloromethane provided the best yields of o-coumaric and melilotic acids. Statistical mixture models indicated that synergic binary interactions, especially those involving ethanol with acetone or chloroform, are important in the Mikania extraction process.

Development of a one-step integrated pressurized liquid extraction and cleanup method for determining polycyclic aromatic hydrocarbons in marine sediments

A rapid and accurate one-step integrated pressurized liquid extraction (PLE) and cleanup method was developed and validated for 34 polycyclic aromatic hydrocarbons in marine sediments, giving an extract that could be analyzed by gas chromatography–mass spectrometry without further cleanup. Marine sediment (5g) was loaded into the stainless-steel extraction cell above activated copper (5g) and activated silica gel (5g). An extraction temperature of 100°C and two 5min extraction cycles using a 4:1 (v/v) hexane–dichloromethane mixture gave a good extraction efficiency. The integrated method gave extracts that were as clean as those obtained using PLE, followed by separate activated copper and silica gel cleanups. The method was validated, in terms of its accuracy, precision, and application using a certified reference material (NIST SRM 1944), marine sediments spiked at low and high concentrations, and contaminated harbor sediments. The mean recoveries were 92% and 94% for the low and high spike concentrations, respectively, and the accuracy was good (giving a mean of 86% of the certified reference material concentrations). The method developed gave a precision and accuracy equal to or better than the precision and accuracy found using PLE with separate cleanups. The method developed gives a shorter sample preparation time and uses much less solvent than PLE and separate cleanups.

Direct Coupling of Cs2CO3and Alcohols for the Synthesis of Dimethyl, Diethyl, and Various Dialkyl Carbonates

Dimethyl carbonate (DMC) has been used in synthetic organic chemistry as a low-toxicity and versatile methylating and carbonylating agent. In industrial processes, DMC is widely used as a fuel additive, electrolyte for lithium ion batteries, and monomer for polycarbonate and polyurethane synthesis. Therefore, an efficient and high-yield synthesis for DMC has been actively investigated. Reaction conditions typically involve either carbon monoxide (CO) or derivatives (e.g., phosgene), or carbon dioxide (CO2) or derivatives (e.g., inorganic carbonates or organic cyclic carbonates). Due to the toxicity and flammability of CO and phosgene, the more environmentally benign and sustainable carbon sources CO2 and derivatives have been actively employed for production of DMC and related acyclic carbonates. The DMC and acyclic carbonate syntheses that have been reported include: 1) transesterification of cyclic carbonates derived from oxirane and CO2; 2) dehydrative condensation of alcohols with CO2; 3) reactions between alkyl halide and metal carbonates; 4) reactions between alcohol, alkyl halide, and CO2; and 5) reactions between alcohol and CO2 in the presence of condensing agents. Other than transesterification of cyclic carbonates, DMC is generated from alcohols or alkyl halide. In terms of chemical cost, use of an alcohol without an extra step for alkyl halide preparation appears more desirable; however, direct coupling of alcohols with CO2 or metal carbonates is challenging. In dehydrative condensation of alcohols with CO2, very efficient dehydrating reagents and metal catalysts are necessary to drive the reaction equilibrium to the product. In direct coupling of alcohols with CO2, alcohol-activation reagents such as the Mitsunobu reagent are required. According to Saito et al., dichloromethane, a common organic solvent, has been used as an alcohol-activating reagent for synthesis of various aliphatic carbonates in the presence of CO2 and Cs2CO3 (base), although synthesis of DMC has not been reported using dichloromethane. In the present study, we used dibromomethane (CH2Br2) as an alcohol-activating reagent and solvent. Using CH2Br2 and an ionic liquid, direct coupling of alcohols with Cs2CO3 in the absence of CO2 was achieved. Using Cs2CO3-mediated conditions, various aliphatic carbonates, including DMC and diethyl carbonate (DEC), were prepared with good yields. Optimization of the synthesis of carbonate 1 is summarized in Table 1. Reaction of cinnamyl alcohol and Cs2CO3 in a mixture of dichloromethane (CH2Cl2) and 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) was carried out at 70 C. Even in the absence of CO2, carbonate 1 was formed with 71% yield (entry 1). In this reaction, Cs2CO3

Tetrathiafulvalene‐Based Macrocycles Formed by Radical Cation Dimerization: The Role of Intramolecular Hydrogen Bonding and Solvent

Compounds 1 a and 1 b were prepared by appending two tetrathiafulvalene (TTF) units to an aromatic amide segment that is driven by six or two intramolecular N-H⋅⋅⋅O hydrogen bonds to adopt a folded conformation. UV/Vis absorption experiments revealed that if the TTF units were oxidized to TTF(·+) radical cations, the two compounds could form a stable single molecular noncovalent macrocycle in less polar dichloromethane or dichloroethane or a bimolecular noncovalent macrocycle in a binary mixture of dichloromethane with a more polar solvent owing to remarkably enhanced dimerization of the TTF(·+) units. The stability of the (TTF(·+))2 dimer was evaluated through UV/Vis absorption, electron paramagnetic resonance, and cyclic voltammetry experiments and also by comparing the results with those of control compound 2. The results showed that introduction of the intramolecular hydrogen bonds played a crucial role in promoting the stability of the (TTF(·+))2 dimer and thus the noncovalent macrocyclization of the two backbones in both uni- and bimolecular manners.