Methylene dichloride

Solvents used for dewaxing are naphtha, propane, sulfur dioxide, acetone—benzene, trichloroethylene, ethylenedichloride—benzene (Barisol), methyl ethyl ketone—benzene (benzol), methyl -butyl ketone, and methyl / -propyl ketone. Other solvents in commercial use for dewaxing include /V-methylpyrrolidinone, MEK—MIBK (methyl isobutyl ketone), dichloroethane—methylene dichloride, and propfyene—acetone. 

A more interesting example is given with PVC and the polycarbonate of bis-phenol A, both slightly crystalline polymers. It is noticed here that whilst methylene dichloride is a good solvent and tetrahydrofuran a poor solvent for the polycarbonate the reverse is true for PVC yet all four materials have similar solubility parameters. It would seem that the explanation is that a form of hydrogen bonding occurs between the polycarbonate and methylene dichloride and between PVC and tetrahydrofuran (Figure 5.7). In other words there is a specific interaction between each solvent pair. 

The process of post-chlorinating PVC was carried out during World War II in order to obtain polymers soluble in low-cost solvents and which could therefore be used for fibres and lacquers. The derivate was generally prepared by passing chlorine through a solution of PVC in tetrachloroethane at between 50°C and 100°C. Solvents for the product included methylene dichloride, butyl acetate and acetone. These materials were of limited value because of their poor colour, poor light stability, shock brittleness and comparatively low softening point. 

In addition to its water solubility poly(vinyl pyrrolidone) is soluble in a very wide range of materials, including aliphatic halogenated hydrocarbons (methylene dichloride, chloroform), many monohydric and polyhdric alcohols (methanol, ethanol, ethylene glycol), some ketones (acetyl acetone) and lactones (a-butyrolactone), lower aliphatic acids (glacial acetic acid) and the nitro-paraffins. The polymer is also compatible with a wide range of other synthetic polymers, with gums and with plasticisers. 

Solvents mentioned include hexane, benzene, liquid sulphur dioxide, chloroform, methylene dichloride and ethyl bromide. Where chlorinated solvents are employed the polymer is separated by addition of methanol, filtered, washed with methanol and the product dried in vacuo at 60°C. 

Because of the cost of pyridine the phosgenation process may be carried out with a mixture of pyridine and a non-hydrohalide-accepting solvent for the polymer and the growing complexes. Suitable solvents include methylene dichloride, tetrachlorethane and chloroform. Although unsubstituted aromatic hydrocarbons may dissolve the solvent they are not effective solvents for the acid chloride-pyridine complexes. 

The resins are resistant to aqueous solutions of acids and alkalis and have a wide range of resistance to solvents. Amongst suitable solvents are methylene dichloride, dimethylformamide and phenol. The films bond well to poly-esterimide resins. 

Chemical Designations - Synonyms Methylene Chloride Methylene Dichloride Chemical Formula CH2CI2. 

A solution of 1 g of the ethyleneketal of the trione in 40 ml of methanol is treated with 0.2 g of sodium borohydride and the mixture is stirred at 20° for 2 hr. Slow drop wise addition of water precipitates the reaction product as crystals. These are filtered, washed with water and dried, to give 1.02 g of hydroxy ketone, which after crystallization from methylene dichloride-hexane has mp 182-184° (reported 184-186°) -23° (CHCI3). 

P-o 3-ketal in 130 ml of glacial acetic acid and 130 ml of water is maintained at 80° for 30 min, poured onto ice, made alkaline with sodium hydroxide and extracted with methylene dichlofide. The extracts are washed once with water, dried over magnesium sulfate, filtered, and evaporated to a residue. A solution of this residue in 240 ml of pyridine and 120 ml of acetic anhydride is kept at room temperature for 1.25 hr and then poured into hydrochloric acid-ice water. The mixture is extracted with methylene dichloride and the methylene dichloride solution is washed until neutral, dried over magnesium sulfate and filtered. The filtrate is evaporated to dryness to yield 13 g. Crystallization from aqueous acetone yields 11.8 g (92%) mp 251-255° [ ]d —1° (dioxane). 

The resulting product is purified by thin layer chromatography on silica gel in methylene dichloride yielding 8)S-di-5a-cholestane-3,6-dione (162) 13 mg, overall yield 26% mp 160-164°, which consists of 83% of dj-species. 

This complex may be prepared in situ as described in experiment 3 below for pyridine or as described by Ratcliffe and Rodehorst for methylene dichloride as solvent. 

Methoxyestra-l,3,5(10),14-tetraen-17-one. A solution of 9.3 g (0.0328 mole) of 3-methoxyestra-l,3,5(10),14-tetraen-17)S-ol in 300 ml of methylene dichloride is added at a rapid dropwise rate to a stirred suspension of 46.5 g (0.18 mole) of the dipyridine-chromium VI complex in 800 ml of methylene dichloride at room temperature. The mixture is stirred 45 min and then filtered. The residue is washed with ethyl acetate and the organic layers are combined. Water is added to the filtrates and sufficient ethyl acetate is added to make the organic layer less dense than water. After the organic layer is washed with water it is dried over sodium sulfate and concentrated to leave... 

A solution of 16jS-methyl-l la,17a,21-trihydroxy-5j5-pregnane-3,20-dione 21-acetate (52), 45 g, in dioxane (297 ml) is cooled to 15° and treated over a 5 min period with a solution of bromine (34.2 g) in dioxane (594 ml) precooled to 18°. After 2 min a solution of sodium acetate (60 g) in water (600 ml) is added and the mixture poured into ice water (8 liters). The precipitate is filtered off, washed to neutrality with water, and dried to give the crude dibromide (53), 55.7 g mp 125-126° (dec.) [aJu 58°. A mixture of dibromide (53), 55.5 g, lithium bromide (27.8 g), lithium carbonate (27.8 g) and DMF (1.11 liters) is refluxed under rapid stirring for 6 hr. The mixture is concentrated under vacuum to about 250 ml, poured into ice water (8 liters) containing hydrochloric acid (250 ml), and extracted with methylene dichloride. The extracts are washed to neutrality with water and evaporated to dryness. The residue is dissolved in acetone, evaporated to dryness under reduced pressure, redissolved in acetone and crystallized by the additon of hexane. This gives the dienone (54) 24.4 g, mp 236-239°. 

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