View source for Dimethyl carbonate

{{distinguish|dimethyl carbate}}
{{chembox
| Watchedfields = changed
| verifiedrevid = 476999619
| Name = Dimethyl carbonate
| ImageFile = Dimethyl carbonate Structural Formulae.svg
| ImageSize = 180px
| ImageName = Dimethyl carbonate
| ImageFile1 = Dimethyl-carbonate-cis-cis-HF-3D-balls.png
| ImageSize1 = 150px
| ImageName1 = Ball-and-stick model of dimethyl carbonate
| IUPACName = Dimethyl carbonate
| OtherNames = DMC<br />Methyl carbonate
|Section1={{Chembox Identifiers
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 36596
| SMILES = COC(=O)OC
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 11526
| PubChem = 12021
| InChI = 1/C3H6O3/c1-5-3(4)6-2/h1-2H3
| InChIKey = IEJIGPNLZYLLBP-UHFFFAOYAC
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C3H6O3/c1-5-3(4)6-2/h1-2H3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = IEJIGPNLZYLLBP-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 616-38-6
  }}
|Section2={{Chembox Properties
| C=3|H=6|O=3
| Appearance = Clear liquid
| Density = 1.069-1.073 g/mL
| Solubility = 13.9 g/100 mL
| MeltingPtC = 2 to 4
| BoilingPtC = 90
| Viscosity = 
  }}
|Section7={{Chembox Hazards
| ExternalSDS =
| MainHazards = Flammable
| FlashPtC = 17
  }}
}}

'''Dimethyl carbonate''' ('''DMC''') is an [[organic compound]] with the [[chemical formula|formula]] OC(OCH<sub>3</sub>)<sub>2</sub>.  It is a colourless, flammable liquid.  It is classified as a [[carbonate ester]]. This compound has found use as a [[methylating agent]] and more recently as a solvent that is exempt from the restrictions placed on most [[volatile organic compound]]s (VOCs) in the US. Dimethyl carbonate is often considered to be a [[green chemistry|green reagent]].<ref>{{Kirk-Othmer | doi = 10.1002/0471238961.0301180204011312.a01.pub2 | title = Chloroformates and Carbonates | year = 2001 | last1 = Kreutzberger | first1 = Charles B.}}</ref>

==Production==
Dimethyl carbonate can be prepared by the reaction of [[phosgene]] with [[methanol]] via [[methyl chloroformate]]:
: COCl<sub>2</sub> + CH<sub>3</sub>OH &rarr; CH<sub>3</sub>OCOCl + HCl
: CH<sub>3</sub>OCOCl + CH<sub>3</sub>OH &rarr; CH<sub>3</sub>OCO<sub>2</sub>CH<sub>3</sub> + HCl

Overall:
: COCl<sub>2</sub> + 2 CH<sub>3</sub>OH &rarr; CH<sub>3</sub>OCO<sub>2</sub>CH<sub>3</sub> + 2 HCl

This historical synthesis process is undesirable because of [[phosgene]]'s toxicity and has been largely replaced by other synthesis routes.  It is produced industrially by a [[transesterification]] of ethylene carbonate or [[propylene carbonate]] and [[methanol]], which also affords respectively ethylene glycol or [[propylene glycol]].  A second large scale commercial synthesis route uses a process where [[carbon monoxide]], methanol and oxygen are reacted to form dimethyl carbonate.<ref name=Tundo/>  World production in 1997 was estimated at 1000 barrels a day.<ref name = pachecho/> Production of dimethyl carbonate worldwide is limited to Asia, the middle east and Europe.

==Reactions and potential applications==

===Methylating agent===
Dimethyl carbonate methylates [[aniline]]s, [[phenols]] and [[carboxylic acid]]s, but many of these reactions require the use of an [[autoclave]].<ref name=Shieh2002>{{cite journal | last = Shieh | first = Wen-Chung |author2=Dell, Stephen |author3=Repič, Oljan | title = Nucleophilic Catalysis with 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) for the Esterification of Carboxylic Acids with Dimethyl Carbonate | journal = [[J. Org. Chem.]] | volume = 67 | issue = 7 | pages = 2188–2191 | year = 2002 | doi =10.1021/jo011036s}}</ref><ref>{{cite journal | doi = 10.1021/ol016949n | pmid = 11784197 | title = 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) and Microwave-Accelerated Green Chemistry in Methylation of Phenols, Indoles, and Benzimidazoles with Dimethyl Carbonate | year = 2001 | last1 = Shieh | first1 = Wen-Chung | last2 = Dell | first2 = Steven | last3 = Repič | first3 = Oljan | journal = Organic Letters | volume = 3 | issue = 26 | pages = 4279–81}}</ref>

:[[Image:DMC Methylation.png|350px|Methylation of phenylacetic acid by dimethyl carbonate promoted by DBU]]

Dimethyl carbonate's main benefit over other methylating reagents such as [[iodomethane]] and [[dimethyl sulfate]] is its much lower toxicity and its biodegradability.<ref name=Tundo>{{cite journal | title = The Chemistry of Dimethyl Carbonate | author = Pietro Tundo | author2 = Maurizio Selva | last-author-amp = yes | journal = [[Acc. Chem. Res.]] | volume = 35 | issue = 9 | year = 2002 | pages = 706–16 | doi = 10.1021/ar010076f}}</ref> Unfortunately, it is a relatively weak [[methylating agent]] compared to these traditional reagents.

===Solvent===
In the US, dimethyl carbonate was exempted under the definition of [[volatile organic compound]]s (VOCs) by the [[U.S. EPA]] in 2009.<ref>http://www.epa.gov/ttn/oarpg/t1/fact_sheets/voc_exemp01011309.pdf.  Information about the EPA's action on exempting dimethyl carbonate as a VOC and petitioner's background information, public comments and other references are available electronically at http://www.regulations.gov, EPA’s electronic public docket and comment system. The docket number for this action is Docket ID No. EPA-HQ-OAR-2006-0948. See http://www.epa.gov/ttn/oarpg/t1pfpr.html and scroll down to Jan 13, 2009 pdf for the rule.</ref>  Due to its classification as VOC exempt, dimethyl carbonate has grown in popularity and applications as a replacement for [[methyl ethyl ketone]] (MEK), [[tert-Butyl acetate|''tert''-butyl acetate]], and [[parachlorobenzotrifluoride]].  Dimethyl carbonate has an ester- or alcohol-like odor, which is more favorable to users than most hydrocarbon solvents it replaces.  Dimethyl carbonate has an evaporation rate of 3.22 (butyl acetate = 1.0), which slightly slower than MEK (3.8) and [[ethyl acetate]] (4.1), and faster than [[toluene]] (2.0) and [[isopropanol]] (1.7).  Dimethyl carbonate has solubility profile similar to common [[glycol ether]]s, meaning dimethyl carbonate can dissolve most common coating resins except perhaps rubber based resins.  Hildebrand solubility parameter is 20.3 Mpa and Hansen solubility parameters are:  dispersion = 15.5, polar = 3.9, H bonding = 9.7.<ref>{{cite book|last1=Kanegsberg|first1=Barbara|last2=Kanegsberg|first2=Edward|title=Handbook for Critical Cleaning: Cleaning Agents and Systems, Second Edition|publisher=CRC Press|isbn=9781439828281|page=16|edition=Second}}</ref>  Dimethyl carbonate is partially soluble in water up to 13%, however it is hydrolyzed in water-based systems over time to methanol and CO<sub>2</sub> unless properly buffered.
Dimethyl carbonate can freeze at same temperatures as water, it can be thawed out with no loss of properties to itself or coatings based on dimethyl carbonate.

===Intermediate in polycarbonate synthesis===
A very large captive use of dimethyl carbonate is for the production of [[diphenyl carbonate]] through [[transesterification]] with [[phenol]]. Diphenyl carbonate is a widely used raw material for the synthesis of bisphenol-A-polycarbonate in a melt polycondensation process. The most common route is described by Fukuoka, of the Japanese "Asahi Kasei" chemical corporation.<ref>Non phosgene Polycarbonate from CO2 - Industrialization of Green Chemical Process, Shinsuke Fukuoka (Asahi Kasei Chemicals Corporation)</ref>

===Alternative fuel additive===
There is also interest in using this compound as a [[fuel oxygenate additive]].<ref name = pachecho>{{cite journal | doi = 10.1021/ef9600974 | journal = [[Energy Fuels]] | title = Review of Dimethyl Carbonate (DMC) Manufacture and Its Characteristics as a Fuel Additive | year = 1997 | last1 = Pacheco | first1 = Michael A. | last2 = Marshall | first2 = Christopher L. | volume = 11 | pages = 2–29}}</ref>

==Safety==
DMC is a flammable liquid with a [[flash point]] of 17&nbsp;°C (63&nbsp;°F), which limits its use in consumer and indoor applications. DMC is still safer than [[acetone]], [[methyl acetate]] and methyl ethyl ketone from a flammability point of view.  DMC has a [[recommended exposure limit]] (REL) limit of 100 ppm by inhalation over an 8-hour work day, which is similar to that of a number of common industrial solvents ([[toluene]], methyl ethyl ketone).  Workers should wear protective organic vapor respirators when using DMC indoors or in other conditions where concentrations exceed the REL.  DMC is metabolized by the body to [[methanol]] and carbon dioxide, so accidental ingestion should be treated in the same manner as [[methanol poisoning]].

==See also==
*[[Dimethyl dicarbonate]]

==References==
<references/>

[[Category:Methylating agents]]
[[Category:Carbonate esters]]
[[Category:Methyl esters]]