Solvents dichloromethane

As an example of an industrially useful radical reaction, look at the chlorination of methane to yield chloromethane. This substitution reaction is the first step in the preparation of the solvents dichloromethane (CHoCl ) and chloroform (CHCI3). 

The most critical decision to be made is the choice of the best solvent to facilitate extraction of the drug residue while minimizing interference. A review of available solubility, logP, and pK /pKb data for the marker residue can become an important first step in the selection of the best extraction solvents to try. A selected list of solvents from the literature methods include individual solvents (n-hexane, " dichloromethane, ethyl acetate, acetone, acetonitrile, methanol, and water ) mixtures of solvents (dichloromethane-methanol-acetic acid, isooctane-ethyl acetate, methanol-water, and acetonitrile-water ), and aqueous buffer solutions (phosphate and sodium sulfate ). Hexane is a very nonpolar solvent and could be chosen as an extraction solvent if the analyte is also very nonpolar. For example, Serrano et al used n-hexane to extract the very nonpolar polychlorinated biphenyls (PCBs) from fat, liver, and kidney of whale. One advantage of using n-hexane as an extraction solvent for fat tissue is that the fat itself will be completely dissolved, but this will necessitate an additional cleanup step to remove the substantial fat matrix. The choice of chlorinated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride should be avoided owing to safety and environmental concerns with these solvents. Diethyl ether and ethyl acetate are other relatively nonpolar solvents that are appropriate for extraction of nonpolar analytes. Diethyl ether or ethyl acetate may also be combined with hexane (or other hydrocarbon solvent) to create an extraction solvent that has a polarity intermediate between the two solvents. For example, Gerhardt et a/. used a combination of isooctane and ethyl acetate for the extraction of several ionophores from various animal tissues. 

Dry the organic solvent layer through 80 g of anhydrous sodium sulfate on a glass funnel and collect the dried solution in a 300-mL round-bottom flask. Evaporate the solvent under reduced pressure. Dissolve the residue in 150 mL of n-hexane and transfer the solution into a 300-mL separatory funnel. Extract twice with 100 mL of acetonitrile. Combine the acetonitrile extracts in a 500-mL round-bottom flask and evaporate the solvent under reduced pressure. Dissolve the residue in a small amount of column-eluting solvent (dichloromethane-n-hexane, 1 1, v/v) and transfer the solution to the top of the silica gel column. After eluting the column with 60 mL of solvent of the same composition (discard), elute orbencarb and I with 150mL of dichloromethane. Collect the eluate in a 300-mL flask and evaporate the solvent under reduced pressure. Dissolve the residue in an appropriate volume of acetone for analysis. 

Costley et al. [113] have evaluated the use of a range of organic solvents (dichloromethane, water, acetone, hexane, xylene) in the microwave extraction of oligomers from PET and have compared MAE to alternative extraction approaches (Soxhlet, Pan-bomb). 

The photocycloaddition of maleic anhydride to acenaphthylene has been studied by Hartmann and Heine.(107a> Irradiation of acenaphthylene in the presence of maleic anhydride in light-atom solvents (dioxane, acetone, or acetonitrile) yields only dimers or copolymers of acenaphthylene. In heavy-atom solvents (dichloromethane, dibromomethane, or iodomethane), however, dimerization is suppressed and cycloaddition with maleic anhydride predominates ... 

Crude methyl diazoacetate contains up to 20% of the solvent dichloromethane. which has to be taken into account when calculating the stoichiometry. The checkers had no problems in preparing, handling, antf using undistilled methyl diazoacetate however, it must be emphasized that this compound is a potential explosive and all operations should be performed behind an effident safety shield. 

RCM of diene 29 using initiator 3 (0.5 equiv) in benzene (0.001 M) at 25°C afforded macrolactones 30 in 86% yield, with a slight preponderance of the desired Z-isomer (Z = 1.7 1). Under similar conditions, triene 34 afforded macrolactones 27 in 65% yield with the undesired isomer predominating (Z =l 2). The Z-macrolactone products had previously been processed to epothilone A (4) [14b, 17a]. The selectivities of these cyclizations are slightly different to those achieved by the Nicolaou [18] and Schinzer [16] groups. The choice of solvent (dichloromethane vs. benzene) is probably responsible for these differences. 

Figure 3.28. Cyclovoltammogram for the hole transporting material Spiro-TAD (36a). The oxidation proceeds in two one-electron and one formal two-electron wave. Solvent Dichloromethane/TBAHFP 0.1 M, Scan rate lOOmV/s. 

It is common practice to choose the supporting electrolyte solely on the basis of its solubility in the solvents used, without paying much attention to the anion of the ammonium salt. For example, when using the solvent dichloromethane, the most convenient supporting electrolyte... 

A modified rare earth catalyst (30) which is based on a polystyrene backbone as depicted in Scheme 4.15 can be applied even in neat water. It is attached via a hydrophobic oligomeric linker which creates a nonpolar reaction environment and acts as a surfactant for the substrates. The reaction of 4-phenyl-2-butanone with tetraallyltin in water using 1.6 mol% of the scandium catalyst (30) afforded the corresponding homoallylalcohol in a yield of 95%. Interestingly, when using other solvents (dichloromethane, acetonitrile, benzene, ethanol, DMF) the yields decreased drastically, indicating a much higher reaction rate in water [98]. 

A rather unexpected product was obtained from the reaction of 2-(methylthio)ethanol and Me2Zn in dichloromethane as a solvent. Instead of the anticipated methylzinc alkoxy compound, a product was obtained with the constitution Mc4Zn4(OCH2CH2SMe)2Cl2 (166). The only possible explanation for the formation of this product is that the chloride present originates from the solvent dichloromethane. An X-ray crystal structure... 

Important for the success in the preparation a proper shell are the ternary phase diagrams of the shell polymer, the core n-tetradecane and the solvent dichloromethane. 

The air samples should be stored in the dark at —20 °C, and the solvent (dichloromethane or DMSO) extracts should be stored in amber-colored, Teflon-lined, screw-capped bottles at —20 °C. These air samples and solvent extracts should come to room temperature prior to use. 

A study of the metabolism of SPI in pig liver was conducted. The polar character of the cysteyl derivatives makes them difficult to extract in chlorinated solvents (dichloromethane, chloroform). As a consequence, extraction with pure MeOH was considered, because it extracted both SPI and its cysteyl metabolites. However, it also extracted other biomolecules interfering with the metabolites. Extractions with pure MeCN were unsuccessful, since liver tissues tended to agglomerate in this medium. Only 40% of the cysteyl conjugates were then extracted. The property of water to disperse the liver tissue was used to develop extraction conditions with MeCN-water (90 10). A good dispersion of the liver was then obtained, and pollution by polar interfering compounds coextracted from the liver was limited. Acetonitrile was evaporated and MeOH was added... 

Figure 5 (Fig. 2 of the original) shows that with both MIPs the increase of wash solvent (dichloromethane) volume has led to cleaner eluates for 4-NP but also the peak area of 4-NP decreased substantially. The chromatograms of the eluates were cleaner when the non-covalent MISPE was used while the retention of 4-NP was better with the semicovalent MISPE. 

The phenomena enumerated in Section 2.4 do not, of course, fully describe all the differences between chemical and electrode processes of ion radical formation. From time to time, effects are found that cannot be clearly interpreted and categorized. For instance, one paper should be mentioned. It bears the symbolic title ir- and a-Diazo Radical Cations Electronic and Molecular Structure of a Chemical Chameleon (Bally et al. 1999). In this work, diphenyldiazomethane and its 15N2, 13C, and Di0 isotopomers, as well as the CH2-CH2 bridged derivative, 5-diazo-10,ll-dihydro-5H-dibenzo[a,d]cycloheptene, were ionized via one-electron electrolytic or chemical oxidation. Both reactions were performed in the same solvent (dichloromethane). Tetra-n-butylammonium tetrafluoroborate served as the supporting salt in the electrolysis. The chemical oxidation was carried out with tris(4-bromophenyl)-or tris(2,4-dibromophenyl)ammoniumyl hexachloroantimonates. Two distinct cation radicals that corresponded to it- and a-types were observed in both types of one-electron oxidation. These electromers are depicted in Scheme 2-28 for the case of diphenyldiazomethane. 

The effect of complexation on redox properties was studied by cyclic voltammetry. Unbound flavin, dissolved in an aprotic solvent (dichloromethane), undergoes a two electron reduction perfectly explained by the ECE mechanism. Upon addition of cyclene ligand and coordination of flavin to the zinc ion complex, the flavohydroquinone redox state was stabilised. 

Aniline (19.8 g, 212.6 mmol, 1.06 eq.) in acetone (50 mL) is added dropwise to a cyanuric chloride suspension (36.8 g, 200 mmol, 1 eq. in 200 mL acetone and 100 mL of ice water), containing NaHC03 (5% w/v), while stirring in an ice bath. When aniline is not detected by thin-layer chromatography (silica, solvent dichloromethane [DCM]), the reaction is stopped by removing acetone in a rotary evaporator. 

Figure 81. Molecular structure of one of the independent molecules in the crystal structure of Au2[p-(CH2)2Ph2P](S2COMe)Br2 the solvent dichloromethane molecule is not shown.

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