dimethyl carbonate
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Dimethyl carbonate (DMC) is an with the OC(OCH3)2. It is a colourless, flammable liquid. It is classified as a . This compound has found use as a and more recently as a solvent that is exempt from the restrictions placed on most s (VOCs) in the US. Dimethyl carbonate is often considered to be a .


Production

World production in 1997 was estimated at 1000 barrels a day. Production of dimethyl carbonate worldwide is limited to Asia, the Middle East, and Europe. Dimethyl carbonate is traditionally prepared by the reaction of and . is produced as an intermediate: : COCl2 + CH3OH → CH3OCOCl + HCl : CH3OCOCl + CH3OH → CH3OCO2CH3 + HCl This synthesis route has been largely replaced by . In this process, and an oxidizer provide the equivalent of CO2+: :: CO + 1/2 O2 + 2 CH3OH → (CH3O)2CO + H2O It can also be produced industrially by a of ethylene carbonate or and , which also affords respectively ethylene glycol or .


Reactions and potential applications


Methylating agent

Dimethyl carbonate methylates s, s, and . Sometimes these reactions require the use of an . : Dimethyl carbonate's main benefit over other methylating reagents such as and is its low toxicity. Additionally, it is biodegradable. Unfortunately, it is a relatively weak compared to these traditional reagents.


Solvent

In the US, dimethyl carbonate was exempted under the definition of s (VOCs) by the in 2009. Due to its classification as VOC exempt, dimethyl carbonate has grown in popularity and applications as a replacement for (MEK) and , as well as until it too was exempted. 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 (4.1), and faster than (2.0) and (1.7). Dimethyl carbonate has solubility profile similar to common 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. Dimethyl carbonate is partially soluble in water up to 13%, however it is hydrolyzed in water-based systems over time to methanol and CO2 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 large captive use of dimethyl carbonate is for the production of through with . Diphenyl carbonate is a widely used raw material for the synthesis of -polycarbonate in a melt polycondensation process, the resulting product being recyclable by reversing the process and transesterifying the polycarbonate with phenol to yield diphenyl carbonate and bisphenol A.


Alternative fuel additive

There is also interest in using this compound as a .{{cite journal , doi = 10.1021/ef9600974 , journal = , 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


Safety

DMC is a flammable liquid with a of 17 °C (63 °F), which limits its use in consumer and indoor applications. DMC is still safer than , and methyl ethyl ketone from a flammability point of view. DMC has a (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 (, 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 and carbon dioxide, so accidental ingestion should be treated in the same manner as .


See also

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References

Methyl esters