Dimethyl terephthalate
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Names | |
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Preferred IUPAC name
Dimethyl benzene-1,4-dicarboxylate | |
Other names
Dimethyl terephthalate
1,4-Benzenedicarboxylic acid dimethyl ester Dimethyl 4-phthalate Dimethyl p-phthalate Di-Me terephthalate Methyl 4-carbomethoxybenzoate Methyl-p-(methoxycarbonyl)benzoate Methyl terephthalate, di- Terephthalic acid dimethyl ester | |
Identifiers | |
3D model (JSmol)
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Abbreviations | DMT |
1107185 | |
ChEBI | |
ChemSpider | |
ECHA InfoCard | 100.004.011 ![]() |
EC Number |
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MeSH | Dimethyl+4-phthalate |
PubChem CID
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RTECS number |
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
C10H10O4 | |
Molar mass | 194.186 g·mol−1 |
Appearance | white solid |
Density | 1.2 g/cm3, ? |
Melting point | 142 °C (288 °F; 415 K) |
Boiling point | 288 °C (550 °F; 561 K) |
Acidity (pKa) | -7.21 |
Basicity (pKb) | -6.60 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
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Infobox references | |
Dimethyl terephthalate (DMT) is an organic compound with the formula C6H4(COOCH3)2. It is the diester formed from terephthalic acid and methanol. It is a white solid that melts to give a distillable colourless liquid.[1]
Production[]
Dimethyl terephthalate (DMT) has been produced in a number of ways. Conventionally, and still of commercial value, is the direct esterification of terephthalic acid. Alternatively, it can be prepared by alternating oxidation and methyl-esterification steps from p-xylene via methyl p-toluate (PT).[1]
Dimethyl terephthalate (DMT) (Witten Process)[]
The common method for the production of DMT from p-xylene (PX) and methanol consists of a multistep process involving both oxidation and esterification. A mixture of p-xylene (PX) and methyl p-toluate is oxidized with air in the presence of a cobalt and manganese catalysts. The acid mixture resulting from the oxidation is esterified with methanol to produce a mixture of esters. The crude ester mixture is distilled to remove all the heavy boilers and residue produced; the lighter esters are recycled to the oxidation section. The raw DMT is then sent to the crystallization section to remove DMT isomers, residual acids and aromatic aldehydes.[2]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/2/20/Monomethyl_terephthalate.png/144px-Monomethyl_terephthalate.png)
Oxidation of methyl p-toluate followed by esterification also yields dimethyl terephthalate (DMT) as shown in the below reaction:[1]
Dimethyl terephthalate (DMT) production through direct esterification
If highly impure terephthalic acid is available, DMT can be made in a separate process by esterification with methanol to dimethyl terephthalate, which is then purified by distillation:
- C8H6O4 + 2CH3OH → C10H10O4 + 2 H2O
at presence of o-xylene at 250–300 °C.
Use[]
DMT is used in the production of polyesters, including polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and polybutylene terephthalate (PBT). It consists of benzene substituted with carboxymethyl groups (CO2CH3) at the 1 and 4 positions. Because DMT is volatile, it is an intermediate in some schemes for the recycling of PET, e.g. from plastic bottles.
Hydrogenation of DMT affords the diol cyclohexanedimethanol, which is a useful monomer.
References[]
- ^ Jump up to: a b c Richard J. Sheehan "Terephthalic Acid, Dimethyl Terephthalate, and Isophthalic Acid" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.doi:10.1002/14356007.a26_193
- ^ "Dimethyl Terephthalate (DMT)". 2013-05-02.
External links[]
- Methyl esters
- Terephthalate esters
- Commodity chemicals