Dichloromethane Chemical Properties
- Melting point:
- -97 °C
- Boiling point:
- 39.8-40 °C mm Hg(lit.)
- 1.325 g/mL at 25 °C(lit.)
- vapor density
- 2.9 (vs air)
- vapor pressure
- 24.45 psi ( 55 °C)
- refractive index
- Flash point:
- storage temp.
- Store at RT.
- Miscible in ethyl acetate, alcohol, hexanes, methanol, diethyl ether, n-octanol, acetone benzene, carbon tetrachloride, diethyl ether and chloroform.
- APHA: ≤10
- Specific Gravity
- 1.329 (20/20℃)
- Odor threshold 160 to 230 ppm
- Odor Threshold
- explosive limit
- Water Solubility
- 20 g/L (20 ºC)
- λ: 235 nm Amax: 1.00
λ: 240 nm Amax: 0.20
λ: 250 nm Amax: 0.05
λ: 260 nm Amax: 0.02
λ: 340-400 nm Amax: 0.01
- Henry's Law Constant
- 2.49 at 30 °C (headspace-GC, Sanz et al., 1997)
- Exposure limits
- TLV-TWA 50 ppm (～175 mg/m3) (ACGIH); carcinogenicity: Suspected Human Carcinogen (ACGIH), Animal Sufficient Evidence, Human Inadequate Evidence (IARC).
- CAS DataBase Reference
- 75-09-2(CAS DataBase Reference)
- NIST Chemistry Reference
- Methylene chloride(75-09-2)
- EPA Substance Registry System
- Methylene chloride (75-09-2)
- Hazard Codes
- Risk Statements
- Safety Statements
- UN 1593 6.1/PG 3
- WGK Germany
- Autoignition Temperature
- 556 °C
- Hazard Note
- HS Code
- 2903 12 00
- Hazardous Substances Data
- 75-09-2(Hazardous Substances Data)
- LD50 orally in young adult rats: 1.6 ml/kg (Kimura)
Dichloromethane Usage And Synthesis
Also known as methylene chloride, dichloromethane (DCM) is a transparent, colorless, volatile halogenated aliphatic hydrocarbon compound with an ether-like mildly sweet smell. It is moderately soluble in water as well as in most organic solvents namely; ether, ethanol, ketones, aldehydes, and phenols (1). Notably, DCM vapors are heavier than air and are normally non-explosive, stable, and non-flammable when exposed in the air; however, temperatures above 100oC must be avoided. Although natural sources do not largely contribute to the global release of DCM, the latter may lead to the formation of the former.
Methylene chloride reacts strongly with active metals such as potassium, sodium, and lithium, and strong bases, for instance, potassium tert-butoxide. However, the compound is incompatible with strong caustics, strong oxidizers, and metals that are chemically active such as magnesium and aluminum powders.
It is noteworthy that methylene chloride can attack some forms of coatings, plastic, and rubber. In addition, dichloromethane reacts with liquid oxygen, sodium-potassium alloy, and nitrogen tetroxide. When the compound comes into contact with water, it corrodes some stainless steels, nickel, copper as well as iron.
When exposed to heat or water, dichloromethane becomes very sensitive as it is subjected to hydrolysis that is hastened by light. Under normal conditions, solutions of DCM such as acetone or ethanol should be stable for 24 hours.
Methylene chloride does not react with alkali metals, zinc, amines, magnesium, as well as alloys of zinc and aluminum. When mixed with nitric acid or dinitrogen pentoxide, the compound can vigorously explode. Methylene chloride is flammable when mixed with methanol vapor in the air.
Since the compound can explode, it is important to avoid certain conditions such as sparks, hot surfaces, open flames, heat, static discharge, and other ignition sources.
Purification and dehydration method
Dichloromethane is safer than chloroform. So it is often used instead of chloroform as the extractant Heavier than water. Ordinary dichloromethane generally can be used directly as extractant. If purification is needed, it can be washed with 5% sodium carbonate solution, and then washed with water, and then dried with anhydrous calcium chloride, distillated to collect 40~41℃ distillate and stored in a brown bottle.
House Hold Uses
The compound is used in bathtub refurbishing. Dichloromethane is highly used industrially in the production of pharmaceuticals, strippers, and process solvents.
Industrial and Manufacturing Uses
DCM is a solvent that is found in varnish and paint strippers, which are often used to remove varnish or paint coatings from various surfaces. As a solvent in the pharmaceutical industry, DCM is used for the preparation of cephalosporin and ampicillin.
Food and Beverage Manufacturing
It is also used in manufacturing beverage and food manufacturing as an extraction solvent. For instance, DCM can be used to decaffeinate unroasted coffee beans as well as tea leaves. The compound is also used in creating hops extract for beer, beverages and other flavoring for foods, as well as in processing spices.
DCM is normally used in the degreasing of metal parts and surfaces, such as railroad equipment and tracks as well as airplane components. It can also be used in degreasing and lubricating products utilized in automotive products, for instance, removal of the gasket and for preparing metal parts for a new gasket.
Experts in automotive commonly use vapor dichloromethane degreasing process to for the removal of grease and oils from car parts of car transistor, spacecraft assemblies, aircraft components, and diesel motors. Today, specialists are able to safely and quickly clean transportation systems using degreasing techniques that depend on methylene chloride.
Dichloromethane is used in laboratories in the extraction of chemicals from foods or plants for medicines such as antibiotics, steroids, and vitamins. In addition, medical equipment can be efficiently and quickly cleaned using dichloromethane cleaners while avoiding damage to heat-sensitive parts and corrosion problems.
Methylene chloride is used as a solvent in the production of cellulose triacetate (CTA), which is applied in the creation of safety films in photography. When dissolved in DCM, CTA begins to evaporate as the fibre of acetate remains behind.
Methylene chloride is used in the production of printed circuit boards in the electronic industry. DCM is utilized to degrease the foil surface of the substrate before the photoresist layer is added to the board.
Dichloromethane enters the human body mainly through inhalation and can cause anesthetic effects such as damages to the respiratory system and the central nervous system. When being used as a paint remover, DCM has been found to be present in high concentrations in indoor environments. The compound can be exposed to the general population through drinking water, air, and food contact, albeit in much smaller levels. Moreover, it is impossible for the compound to accumulate in the atmosphere due to its photolysis rate. Workers who are engaged in the manufacture of DCM, polycarbonate resin and paint remover formulation are at high risk of exposure.
Dichloromethane can be separated by dibutyl phthalate (DBP), then detected by GC with TCD, and quantified by comparison with standard dichloromethane.
Reagents: carrier gas, helium (> 99.5%); carrier for white diatomaceous earth 6201 (40-60 mesh) or equivalent; stationary phase, DBP (in ether); standard dichloromethane, chromatographically pure dichloromethane;
Instruments: a gas chromatograph with TCD, a column, a 3 m x 3 to 4 mm (inner diameter) stainless steel column.
Conditions: fixed phase, 20%:DBP/6021 gasification temperature, 100℃, detection temperature 100℃; carrier gas flow rate, 70ml/min, column temperature of 70 ℃; TCD bridge current, 200mA ~; injection volume, <20μL; temperature. retention time (R) of other chlorinated solvents related to dichloromethane: methyl chloride 0.15; monochloroethane 0.34; 1,1-dichloroethylene 0.59; monochloropropylene, 0.85; carbon tetrachloride 1.86; chloroform 2.47.
ADI gives no specific stipulation (the residual amount of dichloromethane in the products should be minimized as long as the production demand is meet；FAO/WHO。1998)。
Hazards & Safety Information
toxicity grade:WHO Class II
acute toxicity:acute peroral LD50 in rats 1600 mg/kg; mouse intraperitoneal LD50: 437 mg/kg
Physiological stimulation:skin-rabbit 810 mg/24hours Severe; eyes-rabbit 500 mg/24hours Mild
Explosive hazard characteristics:Explosive when mixed with air or oxygen
Combustible hazard characteristics:It releases phosgene when heated. Its vapor is non-flammable
transportation and storing characteristics:In ventilated dry storeroom at low temperature, kept apart from oxidizing agent and nitric acid
extinguishant: Foam extinguisher, carbon dioxide, sprayed water, yellow sand.
professional standard: TWA 350 mg/m3;STEL 879 mg/m3.
A colorless liquid with an ethereal, but penetrating odor. Its miscibility in alcohol and ether and slight solubility in water has made it an ideal solvent and otherwise extremely versatile chemical. It has been used industrially (solvent and paint remover), as a drug (inhalation anesthetic) and as an agricultural chemical (growth regulator and fertilizer). It is narcotic in high concentrations and carcinogenic.
Dichloromethane is a colorless liquid with a mild, sweet odor. It does not occur naturally in the environment. It is made from methane gas or wood alcohol. Industrial uses of dichloromethane are extensive, as a solvent in paint strippers, as a propellant in aerosols, and as a process solvent in the manufacturing of drugs. dichloromethane is also used as a metal cleaning and fi nishing solvent, and it is approved as an extraction solvent for spices and hops. Exposure to dichloromethane occurs in workplaces by breathing fumes from paint strippers that contain it (check the label), breathing fumes from aerosol cans that use it (check the label), and breathing contaminated air near waste sites.
Clear, colorless liquid with a sweet, penetrating, ethereal odor. Leonardos et al. (1969) determined an odor threshold concentration of 214.0 ppmv. The average least detectable odor threshold concentrations of technical grade methylene chloride in water at 60 °C and in air at 40 °C were 5.6 and 24 mg/L, respectively (Alexander et al., 1982).
Methylene chloride is widely used as asolvent, as a degreasing and cleaning reagent,in paint removers, and in extractions oforganic compounds from water for analyses.
Methylene chloride is used principally as a solvent in paint
removers. It is also used as an aerosol propellant, processing
solvent in the manufacture of steroids, antibiotics, vitamins,
and tablet coatings; as a degreasing agent; in electronics
manufacturing; and as a urethane foamblowing agent.Methylene
chloride is also used in metal cleaning, as a solvent in the
production of polycarbonate resins and triacetate fibers, in film
processing, ininkformulations, and as anextraction solvent for
spice oleoresins, caffeine, and hops. It was once registered for
use in the United States as an insecticide for commodity
fumigation of strawberries, citrus fruits, and a variety of grains.
Methylene chloride has been used as a blowing agent for foams and as a solvent for many applications, including coating photographic films, pharmaceuticals, aerosol formulations, and to a large extent in paint stripping formulations. It is used as a solvent in a number of extraction processes, where its high volatility is desirable. It has high solvent power for cellulose esters, fats, oils, resins, and rubber, and is more water soluble than most other chlorinated solvents. Formulations for paint stripping may contain other solvents as well as methylene chloride and are frequently found outside the workplace. These formulations often contain other ingredients that retard evaporation and in the process increase the likelihood of skin irritation.
Dichloromethane was used as an anesthetic gas but is no longer used because of the narrow therapeutic index.
Dichloromethane was first prepared by Regnault in 1840 by the chlorination of methyl chloride in sunlight. It became an industrial chemical of importance during the Second World War. Two commercial processes are currently used for the production of dichloromethane—hydrochlorination of methanol and direct chlorination of methane (Rossberg et al., 1986; Holbrook, 1993).
The predominant method of manufacturing dichloromethane uses as a first step the reaction of hydrogen chloride and methanol to give methyl chloride. Excess methyl chloride is then mixed with chlorine and reacts to give dichloromethane, with chloroform and carbon tetrachloride as co-products. This reaction is usually carried out in the gas phase thermally but can also be performed catalytically or photolytically. At low temperature and high pressure, the liquid-phase process is capable of giving high selectivity for dichloromethane (Rossberg et al., 1986; Holbrook, 1993).
The older and currently less used production method for dichloromethane involves direct reaction of excess methane with chlorine at high temperatures (400–500°C), or at somewhat lower temperatures either catalytically or photolytically. Methyl chloride, chloroform and carbon tetrachloride are also produced as co-products (Rossberg et al., 1986; Holbrook, 1993).
Global production of dichloromethane increased from 93 000 tonnes in 1960 to an estimated 570 000 tonnes in 1980 (IARC, 1986), and is estimated to range from 764 000 to 814 000 tonnes per year from 2005 to 2010 (OECD/SIDS, 2011). In 2009, dichloromethane was produced by 26 manufacturers worldwide and was available from 133 suppliers (NTP, 2011). Production and imports of dichloromethane in the USA totalled 45 000–227 000 tonnes between 1996 and 2006 (NTP, 2011). In the European Union, the total tonnage band for dichloromethane was reported to be 100 000 to 1 000 000 tonnes per year (ECHA, 2016). The production and import of dichloromethane reported in Japan was 58 000 tonnes in 2011 (METI, 2013).
Air & Water Reactions
Methylene chloride is a colourless liquid with a mild, sweet odour. Somewhat water soluble. Subject to slow hydrolysis which is accelerated by light.
Dichloromethane reacts vigorously with active metals such as lithium, sodium and potassium, and with strong bases such as potassium tert-butoxide. Dichloromethane is incompatible with strong oxidizers, strong caustics and chemically active metals such as aluminum or magnesium powders. The liquid will attack some forms of plastic, rubber and coatings. Dichloromethane reacts with sodium-potassium alloy, (potassium hydrogen + N-methyl-N-nitrosurea), nitrogen tetraoxide and liquid oxygen. Dichloromethane also reacts with titanium. On contact with water Dichloromethane corrodes iron, some stainless steels, copper and nickel. Dichloromethane is incompatible with alkali metals. Dichloromethane is incompatible with amines, zinc and alloys of aluminum, magnesium and zinc. Dichloromethane is liable to explode when mixed with dinitrogen pentaoxide or nitric acid. Mixtures of Dichloromethane in air with methanol vapor are flammable.
Toxic. A narcotic. Central nervous systemimpairment and carboxyhemoglobinemia. Possiblecarcinogen.
Dichloromethane is classified as only slightly toxic by the oral and inhalation routes. Exposure to high concentrations of dichloromethane vapor (>500 ppm for 8 h) can lead to lightheadedness, fatigue, weakness, and nausea. Contact of the compound with the eyes causes painful irritation and can lead to conjunctivitis and corneal injury if not promptly removed by washing. Dichloromethane is a mild skin irritant, and upon prolonged contact (e.g., under the cover of clothing or shoes) can cause burns after 30 to 60 min exposure. Dichloromethane is not teratogenic at levels up to 4500 ppm or embryotoxic in rats and mice at levels up to 1250 ppm.
Methylene chloride is a low to moderatelytoxic compound, the toxicity varying withthe animal species. It is less toxic in smallanimals than in humans. The toxic routesof exposure are inhalation of its vapors,ingestion, and absorption through the skin.It may be detected from its odor at a con centration of 300 ppm. Acute toxic symp toms include fatigue, weakness, headache,lightheadedness, euphoria, nausea, and sleep.High concentrations may produce narcosis.Rabbits exposed to 10,000 ppm for 7 hoursdied from exposure. The LC50 value inmice is 14,400 ppm/7 h (NIOSH 1986). Mildeffects may be felt in humans from an 8-hourexposure to 500 ppm of methylene chloride vapors. Oral intake of 15–20 mL ofthe liquid may be lethal to humans. Chronicexposure to this compound can lead to liverinjury. Contact of the liquid with skin or eyescan cause irritation.
Methylene chloride metabolizes in bodyto carbon monoxide, which forms carboxy hemoglobin in blood. The concentration ofthe latter is related to the vapor concentrationand the duration of exposure.
Methylene chloride is carcinogenic to ani mals. Rats inhaling its vapors at concentra tions of 2000–3500 ppm, 5–6 hours per dayfor 2 years developed lung and endocrinetumors. It is a suspected human carcinogen.The evidence of carcinogenicity in humansis inadequate, however.
Special Hazards of Combustion Products: Dissociation products generated in a fire may be irritating or toxic.
Flammability and Explosibility
Noncombustible. Dichloromethane vapor concentrated in a confined or poorly ventilated area can be ignited with a high-energy spark, flame, or high-intensity heat source.
Reactivity with Water No reaction; Reactivity with Common Materials: No reaction; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Not pertinent; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent.
Confirmed carcinogen with experimental carcinogenic and tumorigenic data. Poison by intravenous route. Moderately toxic by ingestion, subcutaneous, and intraperitoneal routes. Mildly toxic by inhalation. Human systemic effects by ingestion and inhalation: paresthesia, somnolence, altered sleep time, convulsions, euphoria, and change in cardlac rate. An experimental teratogen. Experimental reproductive effects. An eye and severe skin irritant. Human mutation data reported. It is flammable in the range of 12-19% in air but ignition is difficult. It will not form explosive mixtures with air at ordinary temperatures. Mixtures in air with methanol vapor are flammable. It will form explosive mixtures with an atmosphere having a high oxygen content, in liquid O2, N2O4, K, Na, NaK. Explosive in the form of vapor when exposed to heat or flame. Reacts violently with Li, NaK, potassiumtert- butoxide, (KOH + N-methyl-Nnitrosourea). It can be decomposed by contact with hot surfaces and open flame, and then yield toxic fumes that are irritating and give warning of their presence. When heated to decomposition it emits highly toxic fumes of phosgene and Cl-.
Methylene chloride is used mainly as a low-temperature extractant of substances which are adversely affected by high temperature. It can be used as a solvent for oil, fats, waxes, bitumen, cellulose acetate; and esters. It is also used as a paint remover; as a degreaser; and in aerosol propellants
Dichloromethane is reasonably anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in experimental animals.
Biological. Complete microbial degradation to carbon dioxide was reported under anaerobic
conditions by mixed or pure cultures. Under enzymatic conditions formaldehyde was the only
product reported (Vogel et al., 1987). In a static-culture-flask screening test, methylene chloride (5
and 10 mg/L) was statically incubated in the dark at 25 °C with yeast extract and settled domestic
wastewater inoculum. After 7 d, 100% biodegradation with rapid adaptation was observed (Tabak
et al., 1981).
Under aerobic conditions with sewage seed or activated sludge, complete biodegradation was observed between 6 h to 1 wk (Rittman and McCarty, 1980).
Soil. Methylene chloride undergoes biodegradation in soil under aerobic and anaerobic conditions. Under aerobic conditions, the following half-lives were reported: 54.8 d in sand (500 ppb); 1.3, 9.4, and 191.4 d at concentrations of 160, 500, and 5,000 ppb, respectively, in sandy loam soil; 12.7 d (500 ppb) in sandy clay loam soil; 7.2 d (500 ppb) following a 50-d lag time. Under anaerobic conditions, the half-life of methylene chloride in clay following a 70-d lag time is 21.5 d (Davis and Madsen, 1991). The estimated volatilization half-life of methylene chloride in soil is 100 d (Jury et al., 1990).
Photolytic. Reported photooxidation products via OH radicals include carbon dioxide, carbon monoxide, formyl chloride, and phosgene (Spence et al., 1976). In the presence of water, phosgene hydrolyzes to HCl and carbon dioxide, whereas formyl chloride hydrolyzes to hydrogen chloride and carbon monoxide (Morrison and Boyd, 1971).
Chemical/Physical. Under laboratory conditions, methylene chloride hydrolyzed with subsequent oxidation and reduction to produce methyl chloride, methanol, formic acid, and formaldehyde (Smith and Dragun, 1984). The experimental half-life for hydrolysis in water at 25 °C is approximately 18 months (Dilling et al., 1975).
UN1593Dichloromethane, Hazard Class: 6.1; Labels: 6.1-Poisonous materials
Shake it with portions of conc H2SO4 until the acid layer remains colourless, then wash with water, aqueous 5% Na2CO3, NaHCO3 or NaOH, then water again. Pre-dry with CaCl2, and distil it from CaSO4, CaH2 or P2O5. Store it away from bright light in a brown bottle with Linde type 4A molecular sieves, in an atmosphere of dry N2. Other purification steps include washing with aqueous Na2S2O3, passage through a column of silica gel, and removal of carbonyl-containing impurities as described under Chloroform. It has also been purified by treatment with basic alumina, distillation, and stored over molecular sieves under nitrogen [Puchot et al. J Am Chem Soc 108 2353 1986]. Dichloromethane from Japanese sources contained MeOH as stabiliser which is not removed by distillation. It can, however, be removed by standing over activated 3A Molecular Sieves (note that 4A Sieves cause the development of pressure in bottles), passed through activated Al2O3 and distilled [Gao et al. J Am Chem Soc 109 5771 1987]. It has been fractionated through a platinum spinning band column, degassed, and distilled onto degassed molecular sieves Linde 4A (heated under high vacuum at over 450o until the pressure readings reached the low values of 10-6 mm, ~1-2hours ). Stabilise it with 0.02% of 2,6-di-tert-butyl-p-cresol [Mohammad & Kosower J Am Chem Soc 93 2713 1971]. [Beilstein 1 IV 35.] Rapid purification: Reflux over CaH2 (5% w/v) and distil it. Store it over 4A molecular sieves.
Incompatible with strong oxidizers, caustics; chemically active metals, such as aluminum, magnesium powders; potassium, lithium, and sodium; concentrated nitric acid causing fire and explosion hazard. Contact with hot surfaces or flames causes decomposition producing fumes of hydrogen chloride and phosgene gas. Attacks some forms of plastics, rubber and coatings. Attacks metals in the presence of moisture.
Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform to EPA regulations governing storage, transportation, treatment, and waste disposal. Incineration, preferably after mixing with another combustible fuel; care must be exercised to assure complete combustion to prevent the formation of phosgene; an acid scrubber is necessary to remove the halo acids produced.
Several jurisdictions have acted to reduce the use and release of various volatile organic compounds, including dichloromethane. The California Air Resources Board was one of the first jurisdictions to regulate dichloromethane; in 1995, it limited the levels of total volatile organic compounds (VOCs) contained in aerosol coating products. Subsequent regulations prevented manufacture, sale, supply, or application of any aerosol coating product containing dichloromethane (Air Resources Board, 2001). California has also prohibited the manufacture, sale, or use of automotive cleaning and degreasing products containing dichloromethane.
In Japan, the environmental quality standards for dichloromethane state that outdoor air levels shall not exceed 0.15 mg/m3 (Ministry of the Environment Government of Japan, 2014).
A guideline value of 3 mg/m3 for 24-hour exposure is recommended by WHO. In addition, the weekly average concentration should not exceed one seventh (0.45 mg/m3) of this 24-hour guideline (WHO, 2000).
In the European Union, the VOC Solvent Emissions Directive (Directive 1999/13/EC) was implemented for new and existing installations on 31 October 2007 (European Commission,1999). The Directive aims to reduce industrial emissions of VOCs from solvent-using activities, such as printing, surface cleaning, vehicle coating, dry cleaning, and manufacture of footwear and pharmaceutical products. Installations conducting such activities are required to comply either with emission limit values or with a reduction scheme. Reduction schemes allow the operator to reduce emissions by alternative means, such as by substituting products with a lower solvent content or changing to solvent-free production processes. The Solvents Directive was implemented in 2010 into the Industrial Emission Directive 2010/75/EU (IED).
Dichloromethane Preparation Products And Raw materials
- Methyl trichloroacetate
- TRICHLOROACETIC ANHYDRIDE
- 2,2,2-TRICHLORO-1,1-DIMETHYLETHYL CHLOROFORMATE
- Ethyl trichloroacetate
- Methylene Blue
- Cobalt chloride
- Methylene Chloride
- 4,4'-Diphenylmethane diisocyanate
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