Solvents methylene chloride

Oxidation. Maleic and fumaric acids are oxidized in aqueous solution by ozone [10028-15-6] (qv) (85). Products of the reaction include glyoxyhc acid [298-12-4], oxalic acid [144-62-7], and formic acid [64-18-6], Catalytic oxidation of aqueous maleic acid occurs with hydrogen peroxide [7722-84-1] in the presence of sodium tungstate(VI) [13472-45-2] (86) and sodium molybdate(VI) [7631-95-0] (87). Both catalyst systems avoid formation of tartaric acid [133-37-9] and produce i j -epoxysuccinic acid [16533-72-5] at pH values above 5. The reaction of maleic anhydride and hydrogen peroxide in an inert solvent (methylene chloride [75-09-2]) gives permaleic acid [4565-24-6], HOOC—CH=CH—CO H (88) which is useful in Baeyer-ViUiger reactions. Both maleate and fumarate [142-42-7] are hydroxylated to tartaric acid using an osmium tetroxide [20816-12-0]/io 2LX.e [15454-31 -6] catalyst system (89). 

The physical properties of methylene chloride are Hsted in Table 1 and the binary a2eotropes in Table 2. Methylene chloride is a volatile Hquid. Although methylene chloride is only slightly soluble in water, it is completely miscible with other grades of chlorinated solvents, diethyl ether, and ethyl alcohol. It dissolves in most other common organic solvents. Methylene chloride is also an excellent solvent for many resins, waxes, and fats, and hence is well suited to a wide variety of industrial uses. Methylene chloride alone exhibits no dash or fire point. However, as Htde as 10 vol % acetone or methyl alcohol is capable of producing a dash point. 

Like many organic solvents, including hexane, heptane, ben2ene, xylene, toluene, gasoline, and particularly some of the other chlorinated and fluorinated solvents, methylene chloride may cause cardiac arrhythmias in the presence of elevated epinephrine when inhaled at concentrations as high as 20,000 ppm (36). 

The salts of 3-acetyl-18/3-glycyrrhetinic acid can be prepared by reaction between 3-acetyl-18/3-glycyrrhetinic acid and an aluminum alcohoiate. Preferably lower alcoholates are used, i.e., alcoholates in which the alkoxy group or groups have from one to four carbon atoms. The salification reaction may be carried out at room temperature or at an elevated temperature in conventional fashion, preferably in the presence of organic solvents. As organic solvents may be used alcohols, ethers, ketones, chlorinated solvents (methylene chloride, chloroform) ethyl acetate, etc. 

Organic solvents that can be used with discrete PEG compounds include DMSO, DMF, DMAC (i 7,N -dimcthylacetamide), and methylene chloride. The compounds also are very soluble in many other commonly used organic solvents, which provide flexibility for doing reactions. DMAC is particularly convenient, because it is easily dried of contaminating water (using molecular sieves), it doesn t decompose like DMF (producing amines), and it doesn t have the odors of some of the other solvents. Methylene chloride can be used for water-insoluble molecules that are to be reacted with the PEG compounds, but don t require subsequent water miscibility. 

Carbodiimides are, in general, useful compounds for effecting certain dehydrative condensations, e.g., in the formation of amides, esters, and anhydrides. These two crystalline water-soluble carbodiimides are especially useful in the synthesis of peptides and in the modification of proteins. The excess of reagent and the co-product (the corresponding urea) are easily separated from products with limited solubility in water. The hydrochloride is best employed in nonaqueous solvents (methylene chloride, acetonitrile, dimethylformamide). The methiodide is relatively stable in neutral aqueous systems, and thus is recommended for those media. 

Large dipole solvents methylene chloride, nitrites, sulfoxides, and... 

Pfizer has implemented a substitution for a range of hazardous solvents (methylene chloride, tetrahydrofuran, toluene, and hexane) in its formulation of Zoloft - the most... 

Figure 5. Thin-layer chromatogram of tris (2,3-dibromopropyl)phosphate on fluorescein impregnated silica gel solvent methylene chloride. Scan in fluorescence quench mom. (a) 3.7 /ig TRIS (b) 0.44 ttg TRIS.

Intersystem crossing rate constants of ortho- and meta-substituted singlet phenylni-trenes are presented in Table 1Mono- and di-o-fluorine substituents have no influence on ISC rate constants.No effect with meta, meta-difluoro substitution is observed either. Pentafluoro substitution has no effect on fcisc in pentane although a modest acceleration is observed in the more polar solvent methylene chloride.i° - i... 

One other solvent, methylene chloride, was also used for resin cleanup but only during the resin blank study. The XAD-4 quaternary resin was stored in the chloride form under water rather than under methanol because our consul-... 

Specific examples illustrate that similar principles affect the absorption spectra. For example, as we have pointed out above, the neutral form of the C-2 benzyl ester is red in MeOH and orange in methylene chloride. Thus it has the spectrum of the ionized form in the polar, protic solvent and of the nonionized form in the nonpolar solvent methylene chloride [248]. The tributyl ammonium salt of the C-2 octyl ester is soluble in solvents ranging from ethanol-water to toluene. Its spectrum in an essentially nonionizing solvent such as toluene is that of the ionized xanthene [249], The spectrum of the pyrillium salt in ethanol is concentration dependent. In dilute solution the compound is totally ionized and is red, whereas in concentrated solution the compound is not fully ionized and the orange form predominates, as predicted by the law of mass action. 

Extraction In order to extract the toxin from the matrix, solvents or mixtures of solvents (methylene chloride, bicarbonate solution, methanol-water, chloroform-water) are used. Two main types of apparatus are commonly used the mechanical shaker (Ultra-Turrax homogenizer, multi-Wrist, magnetic stirrer) or High-Speed Waring Blenders. Other, rarely used extraction procedures are Soxhlet-type extractors and, more recently, supercritical fluid extraction. The time of extraction ranges from a few minutes (3 - 5) to 1 hour, depending on the procedure employed. 

PROBLEM 8.13 The industrial degreasing solvent methylene chloride, CH2C12, is prepared from methane by reaction with chlorine ... 

The distribution coefficient for sulindac between phosphate buffer pH 7.0 and octanol at 25°C is 0.28. Sulindac can be extracted quantitatively from aqueous acidic media into the following organic solvents methylene chloride, chloroform, ethyl acetate and 3 volume % isoamyl alcohol in heptane. Sulindac can be back extracted into dilute alkali from these solvents. 

Suzuki et al. [Ill] screened three solvents—methylene chloride, diethyl ether, and benzene—to determine their ability to produce optimum elution of phthalic acid monoesters sorbed on a styrene divinylbenzene polymer (Figure 2.40). The effect of elution solvent strength on the recovery of the free acid form of the monomethyl (MMP), ethyl (MEP), -propyl (MPRP), K-butyl (MBP), K-pentyl (MPEP), and -octyl (MOP) phthalates is compared. The phthalic acid monoesters are arranged in Figure 2.40 in the order of increasing number of carbons in the alkyl chain, which in turn is roughly correlated with an increase in hydrophobicity. 

Although the FTIR is not used routinely for the assay of thiofanox, in cases where problems from interferences arise or when discrepancies between results occur, the subtraction capabilities of FTIR can be used to obtain quantitative information. Figure 8 contains the spectrum of the extract from the granules, a spectrum of the extraction solvent, methylene chloride, and the difference spectrum. The difference spectrum contains a... 

Solvents. Methylene chloride (Hooker, Dow Chemical, Stauffer, DuPont, Eastman, and Fisher) from most suppliers was satisfactory. After drying over sieves (Linde, Type 3A), the solvent generally contained <10 p.p.m. water, by Karl Fisher water titration. 

The use of paint stripper may lead to damage to the skin from both the sodium hydroxide (caustic soda) and the solvent, methylene chloride. Another, more serious hazard from the paint stripper is the danger of using it in a confined space and inhaling the solvent fumes. Apart from the... 

Reactions between RhCl(PPhj)j or RhClfCOXPPha) and benzyl chloride yield LXXIII, which crystallizes with 0.5 mol solvent (methylene chloride) ... 

Elution solvent methylene chloride, ethyl acetate, acetone, acetonitrile H20/methanol, H20/acetonitrile... 

The BF3/l,3j5-trioxane system is one of the few so far discovered in which there is a possibility that monomeric units add at the cationic end of a macrozwitterion. Fortunately, the cation seems to be stable in the presence of its counter anion. As a simple model system with which to study cationic propagation through zwitterion intermediates it is marred by its equilibrium nature and the insolubility of the polymer. Whilst kinetic termination seems to be absent, the authors report transfer to the solvent methylene chloride. Such a reaction would introduce non-zwitterionic chains. 

Johnston and Pepper35 have found similar behaviour in another anionic polymerization. When dichloromethane was substituted for tetrahydrofuran the rate of amine initiated cyanoacrylate polymerizations fell markedly. The dielectric constants of these two solvents are similar. However, THF is a good donor, weak charge acceptor solvent, methylene chloride the reverse. 

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