CAS number：75-09-2
molecular formula：CH2Cl2
molecular weight：84.93
EINECS number：200-838-9

English synonyms

F30;F30(chlorocarbon);Freon 30;Freon30;HCC30;Khladon30;M-clean D;Metaclen

Related categories

Chromatography and ion-pairing reagents; halogenated compounds; volatile organic compounds (VOCs); agricultural and environmental standards; synthetic material intermediates; alkanes; organic raw materials; solvents and co-solvents; food processing aids; pesticide intermediates; ultra-dry solvent; organic chemical raw material; organic solvent

Introduction

Dichloromethane is a compound formed by replacing two hydrogen atoms in the methane molecule with chlorine, with the molecular formula CH2Cl2. It is a colorless, transparent, heavier than water, volatile liquid with ether-like odor and sweetness. It does not burn, but forms an explosive mixture when mixed with high concentration of oxygen. Dichloromethane is slightly soluble in water, miscible with most common organic solvents, and also miscible with other chlorine-containing solvents, ether, ethanol and N,N-dimethylformamide in any proportion. Dichloromethane is insoluble in liquid ammonia at room temperature, and can be quickly dissolved in phenol, aldehyde, ketone, glacial acetic acid, triethyl phosphate, formamide, cyclohexylamine, and ethyl acetoacetate. Relative density 1.3266 (20/4°C). Melting point -95.1°C. Boiling point 40°C. Non-flammable low boiling point solvent, often used to replace flammable petroleum ether, ether, etc., and can be used as dental local anesthetic, refrigerant and fire extinguishing agent. Auto-ignition point 640°C. Viscosity (20°C) 0.43mPa s. Refractive index nD(20°C) 1.4244. The critical temperature is 237°C and the critical pressure is 6.0795MPa. After pyrolysis, HCl and a trace amount of phosgene are generated, which are heated with water for a long time to generate formaldehyde and HCl. Further chlorination can obtain CHCl3 and CCl4.

Dichloromethane is a halogenated hydrocarbon connected with two chlorine atoms on the same carbon, so it has many properties of halogenated hydrocarbons, such as M-X exchange, oxidative addition, nucleophilic substitution reaction and so on.
Many transition metals can react with methylene chloride, which is why methylene chloride is rarely used as a solvent for metal-catalyzed reactions.
Phosphine compounds have strong nucleophilicity and can undergo nucleophilic substitution reaction with dichloromethane to obtain quaternary phosphonium salt compounds. In addition, phosphorus anion compounds can also undergo nucleophilic substitution reaction with dichloromethane to obtain a product in which two phosphorus atoms react with one methylene group at the same time.
The reaction of amines with halogenated hydrocarbons is called the Menxiukin reaction, and this type of reaction is very reactive.
Dichloromethane is one of the most commonly used solvents, but it should be avoided as much as possible in metal-catalyzed and reaction systems with strong nucleophiles due to its oxidative addition by metals and easy attack by nucleophiles. 

●  It is a non-flammable low boiling point solvent, used as a solvent in the production of cellulose acetate film, aerosol and antibiotics, and vitamins, and also used as an extractant, metal cleaning agent, etc.

●  Dichloromethane is the raw material for the production of the fungicides myclobutanil and imidazole, and is also a good solvent.

●  In addition to organic synthesis, this product is also widely used for cellulose acetate film formation, cellulose triacetate spinning, petroleum dewaxing, aerosol and solvent in the production of antibiotics, vitamins, steroids, and metal surface paint layers Clean degreaser and release agent. In addition, it is also used for grain fumigation and refrigeration of low-pressure freezers and air-conditioning units. It is used as an auxiliary blowing agent in the production of polyether urethane foam and as a blowing agent for extruded polysulfone foam.

●  extraction solvent. For example, it is used to extract caffeine from coffee beans. And used as extraction solvent for hops, spice oleoresin, etc. Color thinner.

●  Used as solvent, also in organic synthesis

●  Used as a solvent in resin and plastic industries. Widely used in medicine, plastic and film industries.

●  Cellulose acetate solvent. Fat and oil extractant. Substitute for ether and petroleum ether.

●  It is obtained by distillation after chlorination of methyl chloride:

●  Mainly use methane chlorination and methanol chlorination. 1. Methane chlorination method Methane, chlorine gas and circulating gas are mixed and sent to the reactor, and the thermal chlorination reaction is carried out at 380-400 ℃. 2. Methanol chlorination method Japan Tokuyama Caoda Company uses methanol and chlorine gas as raw materials to produce methylene chloride. In industry, the method of producing methylene chloride by photochlorination or thermal chlorination with methyl chloride as raw material is also adopted.

●  It is generally obtained by further chlorination of by-product methyl chloride in pesticide production. Chlorination can be done by photo-chlorination or thermal chlorination. The reaction temperature of thermal chlorination should reach 400 °C, which is difficult to produce. Generally, photo-chlorination is used. Reaction equation: CH3Cl+Cl2→CH2Cl2+HCl

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