Dichloromethane(DCM,methylene chloride,ormethylene bichloride) is anorganochlorine compoundwith theformulaCH2Cl2.This colorless, volatile liquid with achloroform-like, sweet odor is widely used as asolvent.Although it is notmisciblewith water, it is slightlypolar,and miscible with many organicsolvents.[12]
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| Names | |||
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| Preferred IUPAC name
Dichloromethane | |||
| Other names
Methylene bichloride; Methylene chloride gas; Methylene dichloride; Solmethine; Narkotil; Solaesthin; Di-clo; Refrigerant-30; Freon-30; R-30; DCM; MDC
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3D model (JSmol)
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| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.000.763 | ||
| EC Number |
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| KEGG | |||
PubChemCID
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| RTECS number |
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| UNII | |||
| UN number | 1593 | ||
CompTox Dashboard(EPA)
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| Properties | |||
| CH2Cl2 | |||
| Molar mass | 84.93g·mol−1 | ||
| Appearance | Colorless liquid | ||
| Odor | Faint,chloroform-like[1] | ||
| Density | 1.3266 g/cm3(20 °C)[2] | ||
| Melting point | −96.7 °C (−142.1 °F; 176.5 K) | ||
| Boiling point | 39.6 °C (103.3 °F; 312.8 K) decomposes at 720 °C[3] 39.75 °C (103.55 °F; 312.90 K) at 760 mmHg[4] | ||
| 25.6 g/L (15 °C) 17.5 g/L (25 °C) 15.8 g/L (30 °C) 5.2 g/L (60 °C)[3] | |||
| Solubility | Miscible inethyl acetate,alcohol,hexanes,benzene,CCl4,diethyl ether,CHCl3 | ||
| logP | 1.19[5] | ||
| Vapor pressure | 0.13 kPa (−70.5 °C) 2 kPa (−40 °C) 19.3 kPa (0 °C) 57.3 kPa (25 °C)[6] 79.99 kPa (35 °C)[3] | ||
| 3.25 L·atm/mol[4] | |||
| −46.6·10−6cm3/mol | |||
Refractive index(nD)
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1.4244 (20 °C)[4][7] | ||
| Viscosity | 0.43 cP (20 °C)[4] 0.413 cP (25 °C) | ||
| Structure | |||
| 1.6 D | |||
| Thermochemistry | |||
| 102.3 J/(mol·K)[6] | |||
Std molar
entropy(S⦵298) |
174.5 J/(mol·K)[6] | ||
Std enthalpy of
formation(ΔfH⦵298) |
−124.3 kJ/mol[6] | ||
Std enthalpy of
combustion(ΔcH⦵298) |
-454.0 kJ/mol (from standard enthalpies of formation)[6] | ||
| Hazards | |||
| Occupational safety and health(OHS/OSH): | |||
Eye hazards
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Irritant | ||
| GHSlabelling:[7] | |||
 
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| Warning | |||
| H315,H319,H335,H336,H351,H373 | |||
| P261,P281,P305+P351+P338 | |||
| NFPA 704(fire diamond) | |||
| Flash point | None, but can form flammable vapor-air mixtures above ≈100 °C[8] | ||
| 556 °C (1,033 °F; 829 K) | |||
| Explosive limits | 13%-23%[1] | ||
| Lethal doseor concentration (LD, LC): | |||
LD50(median dose)
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1.25 g/kg (rats, oral) 2 g/kg (rabbits, oral)[3] | ||
LC50(median concentration)
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24,929 ppm (rat, 30min) 14,400 ppm (mouse, 7h)[10] | ||
LCLo(lowest published)
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5000 ppm (guinea pig, 2 h) 10,000 ppm (rabbit, 7 h) 12,295 ppm (cat, 4.5 h) 14,108 ppm (dog, 7 h)[10] | ||
| NIOSH(US health exposure limits): | |||
PEL(Permissible)
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25 ppm over 8 hours (time-weighted average), 125 ppm over 15 minutes (STEL)[1][9] | ||
REL(Recommended)
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Ca[1] | ||
IDLH(Immediate danger)
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Ca [2300 ppm][1] | ||
| Legal status | |||
| Supplementary data page | |||
| Dichloromethane (data page) | |||
Except where otherwise noted, data are given for materials in theirstandard state(at 25 °C [77 °F], 100 kPa).
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Occurrence
editNatural sources of dichloromethane include oceanic sources,macroalgae,wetlands, and volcanoes.[13]However, the majority of dichloromethane in the environment is the result of industrial emissions.[13]
Production
editDCM is produced bytreatingeitherchloromethaneormethanewith chlorine gas at 400–500 °C. At these temperatures, both methane and chloromethane undergo a series of reactions producing progressively more chlorinated products. In this way, an estimated 400,000 tons were produced in the US, Europe, and Japan in 1993.[12]
The output of these processes is a mixture of chloromethane, dichloromethane,chloroform,andcarbon tetrachlorideas well as hydrogen chloride as a byproduct. These compounds are separated bydistillation.
DCM was first prepared in 1839 by the French chemistHenri Victor Regnault(1810–1878), who isolated it from a mixture ofchloromethaneandchlorinethat had been exposed tosunlight.[14]
Uses
editDCM's volatility and ability to dissolve a wide range of organic compounds makes it a useful solvent for many chemical processes.[12]In thefood industry,it is used todecaffeinatecoffeeandteaas well as to prepare extracts ofhopsand otherflavourings.[15][16]Its volatility has led to its use as anaerosol spray propellantand as ablowing agentforpolyurethane foams.
Specialized uses
edit
The chemical compound's lowboiling pointallows the chemical to function in aheat enginethat can extract mechanical energy from small temperature differences. An example of a DCM heat engine is thedrinking bird.The toy works at room temperature.[17]It is also used as the fluid injukeboxdisplays and holidaybubble lightsthat have a colored bubbling tube above a lamp as a source of heat and a small amount of rock salt to provide thermal mass and a nucleation site for the phase changing solvent.
DCM chemically welds certain plastics. For example, it is used to seal the casing of electric meters. Often sold as a main component ofplastic welding adhesives,it is also used extensively bymodel buildinghobbyists for joining plastic components together. It is commonly referred to as "Di-clo".
It is used in the garment printing industry for removal of heat-sealed garment transfers.
DCM is used in the material testing field ofcivil engineering;specifically it is used during the testing of bituminous materials as a solvent to separate the binder from the aggregate of anasphaltormacadamto allow the testing of the materials.[18]
Dichloromethane extract ofAsparagopsis taxiformis,a seaweedfodderfor cattle, has been found to reduce theirmethane emissionsby 79%.[19]
It has been used as the principal component of various paint and lacquer strippers, although its use is now restricted in the EU and many such products now usebenzyl alcoholas a safer alternative.
Chemical reactions
editDichloromethane is widely used as a solvent in part because it is relatively inert. It does participate in reactions with certain strong nucleophiles however.Tert-butyllithiumdeprotonates DCM:[20]
- H2CCl2+ RLi → HCCl2Li + RH
Methyllithiumreacts with methylene chloride to givechlorocarbene:[citation needed]
- CH2Cl2+ CH3Li → CHCl + CH4+ LiCl
Although DCM is a common solvent in organic chemistry laboratories and is commonly assumed to be inert, it does react with some amines and triazoles.[21]Tertiary amines can react with DCM to form quaternary chloromethyl chloride salts via theMenshutkin reaction.[22]Secondary amines can react with DCM to yield an equilibrium of iminium chlorides and chloromethyl chlorides, which can react with a second equivalent of the secondary amine to formaminals.[23]At increased temperatures,pyridinesincludingDMAP,react with DCM to form methylene bispyridinium dichlorides.[24]Hydroxybenzotriazoleand related reagents used in peptide coupling react with DCM in the presence oftriethylamine,formingacetals.[25]
Toxicity
editSerious health risks are associated with DCM, despite being one of the leasttoxicsimplechlorohydrocarbons.Its highvolatilitymakes it an inhalation hazard.[26][27]It can also be absorbed through the skin.[1][28] Symptoms of acute overexposure to dichloromethane via inhalation include difficulty concentrating,dizziness,fatigue,nausea,headaches,numbness, weakness, and irritation of theupper respiratory tractandeyes.More severe consequences can includesuffocation,loss of consciousness,coma,and death.[1][28]
DCM is also metabolized tocarbon monoxidepotentially leading tocarbon monoxide poisoning.[29]Acute exposure by inhalation has resulted inoptic neuropathy[30]andhepatitis.[31]Prolonged skin contact can result in DCM dissolving some of thefatty tissuesin skin, resulting in skin irritation orchemical burns.[32]
It may becarcinogenic,as it has been linked tocancerof thelungs,liver,andpancreasin laboratory animals.[33]Other animal studies showedbreast cancerandsalivary gland cancer.Research is not yet clear as to what levels may be carcinogenic to humans.[1][28]DCM crosses theplacentabutfetaltoxicity in women who are exposed to it duringpregnancyhas not been proven.[34]In animal experiments, it was fetotoxic at doses that were maternally toxic but noteratogeniceffects were seen.[33]
In people with pre-existing heart problems, exposure to DCM can causeabnormal heart rhythmsand/orheart attacks,sometimes without any other symptoms of overexposure.[28]People with existingliver,nervous system,orskinproblems may worsen after exposure to methylene chloride.[9]
Regulation
editIn many countries, products containing DCM must carry labels warning of its health risks. Concerns about its health effects have led to a search for alternatives in many of its applications.[12][35]
In theEuropean Union,theScientific Committee on Occupational Exposure Limit Values(SCOEL) recommends anoccupational exposure limitfor DCM of 100 ppm (8-hour time-weighted average) and ashort-term exposure limitof 200 ppm for a 15-minute period.[36]TheEuropean Parliamentvoted in 2009 to ban the use of DCM in paint-strippers for consumers and many professionals,[37]with the ban taking effect in December 2010.[38]
In February 2013, the USOccupational Safety and Health Administration(OSHA) and theNational Institute for Occupational Safety and Healthwarned that at least 14 bathtub refinishers have died since 2000 from DCM exposure. These workers had been working alone, in poorly ventilated bathrooms, with inadequate or no respiratory protection, and no training about the hazards of DCM.[9][28][39]OSHA has since then issued a DCM standard.[40]
On March 15, 2019, the USEnvironmental Protection Agency(EPA) issued a final rule to prohibit the manufacture (including importing and exporting), processing, and distribution of DCM in all paint removers for consumer use, effective in 180 days. However, it does not affect other products containing DCM, including many consumer products not intended for paint removal. On April 20, 2023, the EPA proposed a widespread ban on the production of DCM with some exceptions for military and industrial uses.[41]On April 30, 2024, the EPA finalized a ban on most commercial uses of DCM, which mainly banned its application for stripping paint and degreasing surfaces but allowed for some remaining commercial applications, such as chemical production.[42]
Environmental effects
edit
Dichloromethane is not classified as an ozone-depleting substance by theMontreal Protocol.[43]The USClean Air Actdoes not regulate dichloromethane as anozone depleter.[44]Dichloromethane has been classified as a very short-lived substance (VSLS). Despite their short atmospheric lifetimes of less than 0.5 year, VSLSs can contribute to stratospheric ozone depletion, particularly if emitted in regions where rapid transport to the stratosphere occurs.[45]Atmospheric abundances of dichloromethane have been increasing in recent years.
See also
editReferences
edit- ^abcdefghNIOSH Pocket Guide to Chemical Hazards."#0414".National Institute for Occupational Safety and Health(NIOSH).
- ^Haynes, William M., ed. (2011).CRC Handbook of Chemistry and Physics(92nd ed.). Boca Raton, FL:CRC Press.p. 3.164.ISBN1-4398-5511-0.
- ^abcdProperties of Dichloromethane.chemister.ru
- ^abcdCID 6344fromPubChem
- ^"Dichloromethane_msds".
- ^abcdeMethylene chloridein Linstrom, Peter J.; Mallard, William G. (eds.);NIST Chemistry WebBook,NIST Standard Reference Database Number 69,National Institute of Standards and Technology, Gaithersburg (MD) (retrieved 2014-05-26)
- ^abSigma-Aldrich Co.,Dichloromethane.Retrieved on 2014-05-26.
- ^"Real time measurement of dichloromethane containing mixtures"(PDF).Health & Safety Laboratory.Retrieved5 August2015.
- ^abc"Methylene Chloride Hazards for Bathtub Refinishers".OSHA-NIOSH Hazard Alert 2013-110.OSHA and NIOSH.Retrieved22 January2015.
- ^ab"methylene chloride".Immediately Dangerous to Life or Health Concentrations (IDLH).National Institute for Occupational Safety and Health(NIOSH).
- ^Anvisa(2023-03-31)."RDC Nº 784 - Listas de Substâncias Entorpecentes, Psicotrópicas, Precursoras e Outras sob Controle Especial"[Collegiate Board Resolution No. 784 - Lists of Narcotic, Psychotropic, Precursor, and Other Substances under Special Control] (in Brazilian Portuguese).Diário Oficial da União(published 2023-04-04).Archivedfrom the original on 2023-08-03.Retrieved2023-08-16.
- ^abcdRossberg, M.et al.(2006) "Chlorinated Hydrocarbons" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim.doi:10.1002/14356007.a06_233.pub2.
- ^abGribble, Gordon W. (2009).Naturally Occurring Organohalogen Compounds.Springer.ISBN978-3211993248.
- ^Regnault, V. (1839) "De l'action du chlore sur les éthers hydrochloriques de l'alcool et de l'esprit de bois, et de plusieurs points de la théorie des éthers" (On the action of chlorine on the hydrochloric ethers of ethanol and methanol, and on several points of the theory of ethers),Annales de chimie et physique,series 2,71:353–431; see especially:"Seconde partie. De l'action du chlore sur l'éther hydrochlorique de l'esprit de bois"(Second part. On the action of chlorine on the hydrochloric ether of methanol [i.e., chloromethane]), pages 377–380. Regnault gives dichloromethane the nameéther hydrochlorique monochloruré(monochlorinated hydrochloric ether). Note: Regnault gives the empirical formula for dichloromethane as C2H4Cl4because during that era, chemists used incorrect atomic masses.
Reprinted in German in:- Regnault, V. (1840)."Ueber die Einwirkung des Chlors auf die Chlorwasserstoffäther des Alkohols und Holzgeistes und über mehrere Punkte der Aethertheorie".Annalen der Chemie und Pharmacie.33(3): 310–334.doi:10.1002/jlac.18400330306.See p. 328.
- Regnault, V. (1840)."Ueber die Wirkung des Chlors auf den Chlorwasserstoffäther des Alkohols und des Holzgeistes, so wie über mehrere Puncte der Aethertheorie".Journal für Praktische Chemie.19:193–218.doi:10.1002/prac.18400190134.See p. 210.
- ^Office of Environmental Health Hazard Assessment (September 2000)."Dichloromethane"(PDF).Public Health Goals for Chemicals in Drinking Water.California Environmental Protection Agency.RetrievedJune 5,2016.[permanent dead link]
- ^James2014-04-09T00:00:00+01:00, Emily."Dichloromethane".Chemistry World.
{{cite web}}:CS1 maint: numeric names: authors list (link) - ^Perelman, Yakov (1972) [1936].Physics for Entertainment.Vol. 2. Hyperion Books. pp. 175–178.ISBN978-1401309213.[1][2]
- ^Shell Bitumen(2003-09-25).The Shell Bitumen Handbook.Thomas Telford.ISBN978-0-7277-3220-0.
- ^Machado, Lorenna; Magnusson, Marie; Paul, Nicholas; Tomkins, Nigel (2016)."Identification of bioactives from the red seaweedAsparagopsis taxiformisthat promote antimethanogenic activity in vitro ".Journal of Applied Phycology.28(5): 3117–3126.Bibcode:2016JAPco..28.3117M.doi:10.1007/s10811-016-0830-7.
- ^Matteson, Donald S.; Majumdar, Debesh (1983). "Homologation of boronic esters to.alpha.-chloro boronic esters".Organometallics.2(11): 1529–1535.doi:10.1021/om50005a008.
- ^Mills, John E.; Maryanoff, Cynthia A.; Cosgrove, Robin M.; Scott, Lorraine; McComsey, David F. (1984)."The Reaction of Amines with Methylene Chloride. A Brief Review".Organic Preparations and Procedures International.16(2): 97–114.doi:10.1080/00304948409356172.ISSN0030-4948.
- ^Dunlap, Lee E.; Olson, David E. (2018-05-31)."Reaction of N, N -Dimethyltryptamine with Dichloromethane Under Common Experimental Conditions".ACS Omega.3(5): 4968–4973.doi:10.1021/acsomega.8b00507.ISSN2470-1343.PMC5981293.PMID29876537.
- ^Mills, John E.; Maryanoff, Cynthia A.; McComsey, David F.; Stanzione, Robin C.; Scott, Lorraine (1987)."Reaction of amines with methylene chloride. Evidence for rapid aminal formation from N-methylenepyrrolidinium chloride and pyrrolidine".The Journal of Organic Chemistry.52(9): 1857–1859.doi:10.1021/jo00385a038.ISSN0022-3263.
- ^Rudine, Alexander B.; Walter, Michael G.; Wamser, Carl C. (2010-06-18)."Reaction of Dichloromethane with Pyridine Derivatives under Ambient Conditions".The Journal of Organic Chemistry.75(12): 4292–4295.doi:10.1021/jo100276m.ISSN0022-3263.PMID20469919.
- ^Ji, Jian-guo; Zhang, De-yi; Ye, Yun-hua; Xing, Qi-yi (1998)."Studies on the reactions of HOBt, HOOBt, HOSu with dichloroalkane solvents".Tetrahedron Letters.39(36): 6515–6516.doi:10.1016/S0040-4039(98)01406-3.
- ^Rioux JP, Myers RA (1988). "Methylene chloride poisoning: a paradigmatic review".J Emerg Med.6(3): 227–238.doi:10.1016/0736-4679(88)90330-7.PMID3049777.
- ^CDC (2012)."Fatal Exposure to Methylene Chloride Among Bathtub Refinishers — United States, 2000–2011".MMWR.61(7): 119–122.PMID22357403.
- ^abcdeHall, Ronald M. (4 February 2013)."Dangers of Bathtub Refinishing".National Institute for Occupational Safety and Health.Retrieved21 January2015.
- ^Fagin J, Bradley J, Williams D (1980)."Carbon monoxide poisoning secondary to inhaling methylene chloride".Br Med J.281(6253): 1461.doi:10.1136/bmj.281.6253.1461.PMC1714874.PMID7437838.
- ^Kobayashi A, Ando A, Tagami N, Kitagawa M, Kawai E, Akioka M, Arai E, Nakatani T, Nakano S, Matsui Y, Matsumura M (2008). "Severe optic neuropathy caused by dichloromethane inhalation".J Ocul Pharmacol and Ther.24(6): 607–612.doi:10.1089/jop.2007.0100.PMID19049266.
- ^Cordes DH, Brown WD, Quinn KM (1988)."Chemically induced hepatitis after inhaling organic solvents".West J Med.148(4): 458–460.PMC1026148.PMID3388849.
- ^Wells GG, Waldron HA (1984)."Methylene chloride burns".Br J Ind Med.41(3): 420.doi:10.1136/oem.41.3.420.PMC1009322.PMID6743591.
- ^abUSDHHS."Toxicological Profile for Methylene Chloride"(PDF).Retrieved2006-09-10.
- ^Bell BP, Franks P, Hildreth N, Melius J (1991). "Methylene chloride exposure and birthweight in Monroe County, New York".Environ Res.55(1): 31–9.Bibcode:1991ER.....55...31B.doi:10.1016/S0013-9351(05)80138-0.PMID1855488.
- ^"Summary of Regulations Controlling Air Emissions from Paint Stripping and Miscellaneous Surface Coating Operations"(PDF).NESHAP (Subpart HHHHHH).US Environmental Protection Agency. April 2008. Archived fromthe original(PDF)on 2016-11-23.
- ^Recommendation from the Scientific Committee on Occupational Exposure Limits for methylene chloride (dichloromethane)(PDF).European Chemicals Agency(Report). June 2009.Retrieved2023-09-07.
- ^"EU Banning Most DCM Paint Strippers".PaintSquare News.2012-03-09.Retrieved2023-09-07.
- ^"COMMISSION REGULATION (EU) No 276/2010 (Official Journal of the European Union, L 86/7)".2010-04-01.Retrieved2012-02-07.
- ^OSHA QuickTakes,February 1, 2013;
- ^Methylene Chloride.Occupational Safety & Health Administration. osha.gov
- ^"EPA Proposes Ban on All Consumer, Most Industrial and Commercial Uses of Methylene Chloride to Protect Public Health".2023-04-20.
- ^"Biden-Harris Administration Finalizes Ban on Most Uses of Methylene Chloride, Protecting Workers and Communities from Fatal Exposure".2024-04-30.
- ^United States Environmental Protection Agency (2015-07-17)."Ozone-Depleting Substances".RetrievedApril 20,2018.
- ^United States Environmental Protection Agency (October 1995)."Questions and Answers on Ozone-Depleting Solvents and Their Substitutes".RetrievedApril 20,2018.
- ^World Meteorological Organization, United Nations Environmental Program (15 April 2020)."Scientific Assessment of Ozone Depletion: 2018".Archived fromthe originalon December 18, 2023.
External links
edit
- International Chemical Safety Card 0058
- NIOSH Pocket Guide to Chemical Hazards."#0414".National Institute for Occupational Safety and Health(NIOSH).
- National Pollutant Inventory – Dichloromethane Fact Sheet
- Dichloromethane at National Toxicology Program
- IARC Summaries & Evaluations Vol. 71 (1999)
- Canadian Environmental Protection Act Priority Substances List Assessment Report
- Organic Compounds Database
- Sustainable uses and Industry recommendations