Dichloromethane solvent properties

Above the critical temperature and pressure, a substance is referred to as a supercritical fluid. Such fluids have unusual solvent properties that have led to many practical applications. Supercritical carbon dioxide is used most commonly because it is cheap, nontoxic, and relatively easy to liquefy (critical T = 31°C, P = 73 atm). It was first used more than 20 years ago to extract caffeine from coffee dichloromethane, CH2C12, long used for this purpose, is both a narcotic and a potential carcinogen. Today more than 10s metric tons of decaf coffee are made annually using supercritical C02. It is also used on a large scale to extract nicotine from tobacco and various objectionable impurities from the hops used to make beer. 

Most of the current applications of dichloromethane are based on its solvent properties. For use in paint strippers, one of its first applications, dichloromethane is blended with other chemical components to maximize its effectiveness against specific coatings. Typical additives include alcohols, acids, amines or ammonium hydroxide, detergents and paraffin wax (Rossberg et al., 1986 Holbrook, 1993 WHO, 1996). 

The photophysical and photochemical properties of the binuclear [Au2 (dppf)(C=CR)2] (R = Ph and fBu) were studied [82]. The complexes were non-emissive in the solid state even at 77 K, but emission bands at 410 nm in dichloromethane could be observed. The photoreaction between [Au2(dppf)(C=CPh)2] and the dichloromethane solvent was probed, which led to the formation of the organic C-C coupled product, PhC=CC=CPh, and the inorganic [Au2(dppf)Cl2] complex. 

Work in solution also offers some verification of this sort of behavior. For example, by pairing 1 -methylimidazole with a series of acids with varying pK, NMR and IR data indicated a gradual shift of the proton from the acid to the base . Similar properties have been noted in the complex involving acetic acid and pyridine, in a variety of eoneentration situations , and also when substituted pyridines are paired with trifluoroacetate in dichloromethane solvent. ... 

Gestblom, B., and Songstad, J. Solvent properties of dichloromethane. VI. Dielectric properties of electrolytes in dichloromethane. Acta Chem. Scand. Ser. B, 1987,41, p. 396-400. 

Dichloromethane is a volatile liquid with excellent solvent properties for nonpolar organic solutes. It has been used as a solvent for the decaffeination of coffee, in paint strippers, as a blowing agent in urethane polymer manufacture, and to depress vapor pressure in aerosol formulations. Once commonly sold as a solvent and stain remover, highly toxic carbon tetrachloride is now largely restricted to... 

Small amounts of other solvents are added to obtain the desired retention, increase solubility, and improve resolution. Chlorinated solvents (e.g., chloroform, dichloromethane) are frequently used for this purpose on account of their good solvent properties and effects on selectivity, although these solvents can be contaminated with traces of HCl. Other solvents used as modifiers are THF, ethyl acetate, hexane, acetone, and water. In some cases, methanol has been added to an acetonitrile-based mobile phase. Craft [100] investigated nine solvent modifiers and found THF to be the most beneficial modifier of methanol. Analysts tend to... 

The data are reproduced in Table 1.2, below. Note that chloroform seems to be the best solvent, but recall also that it can readily be deprotonated. Dichloromethane and 1,2-dichloroethane seem to be about equally effective in solvating the salts, but methylene chloride is less prone to undergo substitution than dichloroethane, although the latter s higher boiling point can be an advantage. We also note that in at least one case, special solvent properties have been attributed to ethyl acetate [56]. 

The third work of modification of the solvent properties consisted of studying different organic solvents having the same dielectric constant but different viscosities. The solvents studied were dichloromethane, 1,2-dichloroethane, and 1,2-dichlorobenzene. Again the results obtained can be summarized as follows ... 

Most BF3 affinities in Table 3.3 are primary values measured in dichloromethane. This solvent was chosen because it can dissolve most BF3 complexes, while being rather inert (low hydrogen-bond acidity, Lewis basicity and relative permittivity). Nitrobenzene also exhibits good solvent properties towards BF3 complexes, and some measurements were run on representative bases, in both C6H5NO2 and CH2CI2. A very good linear relationship was observed [5] between the enthalpy changes of reaction 3.4 in dichloromethane and nitrobenzene ... 

Bonhote and co-workers [10] reported that ILs containing triflate, perfluorocar-boxylate, and bistrifylimide anions were miscible with liquids of medium to high dielectric constant (e), including short-chain alcohols, ketones, dichloromethane, and THF, while being immiscible with low dielectric constant materials such as alkanes, dioxane, toluene, and diethyl ether. It was noted that ethyl acetate (e = 6.04) is miscible with the less-polar bistrifylimide and triflate ILs, and only partially miscible with more polar ILs containing carboxylate anions. Brennecke [15] has described miscibility measurements for a series of organic solvents with ILs with complementary results based on bulk properties. 

In a recent study, poly(aryl ether) dendritic branches terminated with triethyleneglycol chains were attached to Cgg [66] dendrimer 32 represents the fourth generation. The photophysical properties of these fullerodendrimers have been systematically investigated in three solvents, namely toluene, dichloromethane, and acetonitrile. On increasing dendrimer generation, it has been found that in each solvent (i) the maximum of the fullerene fluorescence band is red-shifted... 

The red and orange forms of RhCl[P(C6H5)3]3 have apparently identical chemical properties the difference is presumably due to different crystalline forms, and possibly bonding in the solid. The complex is soluble in chloroform and methylene chloride (dichloromethane) to about 20 g./l. at 25°. The solubility in benzene or toluene is about 2 g./l. at 25° but is very much lower in acetic acid, acetone, and other ketones, methanol, and lower aliphatic alcohols. In paraffins and cyclohexane, the complex is virtually insoluble. Donor solvents such as pyridine, dimethyl sulfoxide, or acetonitrile dissolve the complex with reaction, initially to give complexes of the type RhCl[P(C6H6)3]2L, but further reaction with displacement of phosphine may occur. 

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