Dimethyl carbonate

Organic compound

Collection

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This entry is made by China Science and Technology Information Magazine Participate in editing and review Science Popularization China · Science Encyclopedia authentication.

Dimethyl carbonate is an organic compound with chemical formula C three H six O three It is a chemical raw material with low toxicity, excellent environmental protection performance and wide use. It is an important organic synthesis intermediate. Its molecular structure contains carbonyl , methyl and Methoxy It has a variety of reaction properties and is safe, convenient, less polluting and easy to transport in production.

Chinese name: Dimethyl carbonate^[1]
Foreign name: Dimethyl carbonate，DMC
Alias: Methyl carbonate; DMC； Ethane carbonate
chemical formula: C three H six O three^[1]
molecular weight: ninety point zero seven eight^[1]
CAS login number: 616-38-6^[1]
EINECS login number: 210-478-4^[1]
Melting point: 0.5 ℃
Boiling point: 90 to 91 ℃

Water solubility: Insoluble
Density: 1.07 g/cm³
Appearance: Colorless liquid with aromatic smell
Flash point: 17 ℃ （OC）
Security description: S9；S16^[1]
Hazard symbol: F^[1]
Hazard description: R11^[1]
UN dangerous goods number: one thousand one hundred and sixty-one^[1]
critical temperature: 274.85℃

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Physical and chemical properties

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^[1]

Saturated vapor pressure: 7.38kPa (25 ℃)^[1]

Critical pressure: 4.5MPa^[1]

Upper explosive limit（ V / V ）：20.5%^[1]

Lower explosive limit（ V / V ）：3.1%^[1]

Solubility: miscible in most organic solvents, and miscible in acids and bases

Molecular structure data

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Molar refractive index: 19.46^[1]

Molar volume (cm three /mol）：87.9^[1]

Isotonic specific volume (90.2K): 195.9^[1]

Surface tension (dyne/cm): 24.6^[1]

Polarization (10 -24 cm three ）：7.71^[2]

Calculate chemical data

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Reference value for drainage parameter calculation (XlogP): 0.5^[1]

Number of hydrogen bond donors: 0^[1]

Number of hydrogen bond receptors: 3^[1]

Number of rotatable chemical bonds: 2^[1]

Number of tautomers: 0

Topological molecular polar surface area: 35.5^[1]

Number of heavy atoms: 6^[1]

Surface charge: 0^[1]

Complexity: 44^[1]

Number of isotope atoms: 0^[1]

Determine the number of atomic structure centers: 0^[1]

Number of uncertain atomic structure centers: 0^[1]

Determine the number of chemical bond structure centers: 0^[1]

Number of uncertain chemical bond structure centers: 0^[1]

Number of covalent bond units: 1^[2]

purpose

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Substitute phosgene as carbonylation agent

Phosgene is highly reactive, but its toxic and highly corrosive by-products make it face huge environmental pressure, so it will be gradually eliminated; DMC has similar nucleophilic reaction center. When the carbonyl group of DMC is attacked by nucleophilic reaction, the acyl oxygen bond breaks to form carbonyl compounds, and the by-product is methanol. Therefore, DMC can replace phosgene as a safe reaction agent to synthesize carbonic acid derivatives, such as Carbamate pesticide , polycarbonate, isocyanate, etc., of which polycarbonate will be the field with the largest demand for DMC. It is predicted that more than 80% of DMC will be used to produce polycarbonate in 2005.

Substitute dimethyl sulfate as methylation agent

For reasons similar to phosgene, dimethyl sulfate is also faced with the pressure of being eliminated. When the methyl carbon of DMC is attacked by nucleophilic, its alkyl oxygen bond breaks, which also generates methylation products. Moreover, DMC has higher reaction yield and simpler process than dimethyl sulfate. Its main uses include synthetic organic intermediates, pharmaceutical products, pesticide products, etc.

Low toxic solvent

DMC has excellent solubility, narrow melting and boiling point range, high surface tension, low viscosity, low dielectric constant of medium, high evaporation temperature and fast evaporation speed, so it can be used as a low toxic solvent in the coating industry and pharmaceutical industry. It can be seen that DMC is not only less toxic, but also has the characteristics of high flash point, low vapor pressure and high lower explosive limit in the air. Therefore, it is a green solvent that combines cleanliness and safety.

Performance comparison between DMC and other solvents
performance	DMC	acetone	Isobutanol	Trichloroethane	toluene
molecular weight	ninety point zero eight	fifty-eight point zero eight	sixty point zero nine	one hundred and thirty-three point four one	ninety-two point one
Melting point/℃	2-4	-94.2	-88.5	-32.6	-94.97
Boiling point/℃	ninety	fifty-six point one	eighty-two point three	seventy-four point one	one hundred and ten point six
Flash point (closed)/℃	eighteen point three	-18	eleven point seven	-	four point four
Vapor pressure (20 ℃)/kPa	five point six zero	twenty-four point six six	four point two seven	thirteen point three three	two point nine three
Explosion limit/%	3.8～21.3	2.15～13	2.7～13.0	-	1.27～7.0
Viscosity/× 10 -3 Pa·s	zero point six two five	zero point three one six	two point four one	zero point seven nine	zero point five seven nine
Surface tension/× 10 -5 N·cm	twenty-four point six	-	twenty point eight	twenty-five point six	twenty-seven point nine two
Steam heat/J · g -1	-1369.06	five hundred and twenty-three	six hundred and seventy-six point five eight	two hundred and forty-nine point eight two	three hundred and sixty-three point six nine
Dielectric constant	two point six	one point zero one	eighteen point six	seven point one two	two point two
Relative evaporation rate	four point six	seven point two	zero point eight three	-	two point four
SP value	ten point four	ten	ten point nine	eight point six	eight point four
LD fifty /mg·kg -1	one hundred and twelve thousand and nine hundred	-	five thousand and eight hundred	-	seven thousand five hundred and thirty
Hygienic allowable concentration/mg · L -1	one	-	zero point four zero	zero point two zero	200×10 -6

Gasoline additive

DMC has the properties of high oxygen content (up to 53% oxygen content in the molecule), excellent octane number improvement, phase free separation, low toxicity and rapid biodegradability, which makes the amount ratio of DMC used when gasoline reaches the same oxygen content Methyl tert butyl ether (MTBE) is 4.5 times less, thus reducing the total emissions of hydrocarbons, carbon monoxide and formaldehyde in vehicle exhaust. In addition, it overcomes the shortcomings of common gasoline additives that are easily soluble in water and pollute groundwater. Therefore, DMC will become one of the most potential gasoline additives to replace MTBE.

Storage and transportation

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Precautions for storage: flammable, whose vapor can form explosive mixture when mixed with air, and stored in a cool, dry and well ventilated incombustible warehouse. Keep away from kindling and heat sources. The warehouse temperature should not exceed 37 ℃. Keep container sealed. It shall be stored separately from oxidants, reducing agents, acids, etc., and shall not be mixed. Explosion proof lighting and ventilation facilities shall be adopted. It is prohibited to use mechanical equipment and tools that are easy to generate sparks. The storage area shall be equipped with leakage emergency treatment equipment and suitable materials for storage in a cool, dry and well ventilated incombustible warehouse.

Precautions for transportation: packing mark Packing method of flammable liquid Ordinary wooden case outside ampoule bottle; Precautions for the transportation of threaded glass bottles, iron cap pressure glass bottles, plastic bottles or ordinary wooden boxes outside metal barrels (cans) The transportation vehicles shall be equipped with corresponding types and quantities of fire-fighting equipment and leakage emergency treatment equipment. It is better to transport in the morning and evening in summer. The tank (tank) car used for transportation shall be equipped with grounding chain, and the tank can be equipped with hole partition to reduce static electricity generated by vibration. It is strictly prohibited to mix with oxidants, reducing agents, acids, edible chemicals, etc. During transportation, it shall be protected from sun exposure, rain and high temperature. Keep away from kindling, heat source and high temperature area during stopover. The exhaust pipe of the vehicle transporting this article must be equipped with fire arresting device.