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Dimethyl terephthalate

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(Redirected from Dimethylterephthalate) Not to be confused with the psychoactive chemical N,N-Dimethyltryptamine, which is also commonly abbreviated as DMT.
Dimethyl terephthalate
Structural formula of dimethyl terephthalate
Names
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 (2:1)
Identifiers
CAS Number
3D model (JSmol)
Abbreviations DMT
Beilstein Reference 1107185
ChEBI
ChemSpider
ECHA InfoCard 100.004.011 Edit this at Wikidata
EC Number
  • 204-411-8
MeSH Dimethyl+4-phthalate
PubChem CID
RTECS number
  • WZ1225000
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/C10H10O4/c1-13-9(11)7-3-5-8(6-4-7)10(12)14-2/h3-6H,1-2H3Key: WOZVHXUHUFLZGK-UHFFFAOYSA-N
  • InChI=1/C10H10O4/c1-13-9(11)7-3-5-8(6-4-7)10(12)14-2/h3-6H,1-2H3Key: WOZVHXUHUFLZGK-UHFFFAOYSA-N
SMILES
  • COC(=O)C1=CC=C(C=C1)C(=O)OC
  • O=C(OC)c1ccc(cc1)C(=O)OC
Properties
Chemical formula C10H10O4
Molar mass 194.186 g·mol
Appearance white solid
Density 1.2 g/cm, ?
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 , 100 kPa). checkY verify (what is  ?) Infobox references
Chemical compound

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.

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).

Dimethyl terephthalate by the Witten process

The 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 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 then distilled to remove all the heavy boilers and residue that are produced; lighter esters such as monomethyl terephthalate 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.

Structure of monomethyl terephthalate

Oxidation of methyl p-toluate followed by esterification also yields dimethyl terephthalate (DMT) as shown in the below reaction:

Esterification of the resulting acid with methanol

Dimethyl terephthalate by direct esterification

DMT can also be made by a different route, namely direct esterification of terephthalic acid with methanol. The dimethyl terephthalate that is formed is then purified by distillation. Even terephthalic acid of low purity may be used in this method.

C8H6O4 + 2CH3OH → C10H10O4 + 2 H2O

in the presence of o-xylene at 250–300 °C.

Uses

DMT is used in the production of polyesters, including polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and polybutylene terephthalate (PBT). Structurally, DMT consists of a benzene ring substituted at the 1 and 4 positions with methyl carboxylate (-CO2CH3) groups. 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

  1. ^ 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
  2. "Dimethyl Terephthalate (DMT)". 2013-05-02. Archived from the original on 2017-10-07. Retrieved 2015-03-05.

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