Dimethyl terephthalate

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Dimethyl terephthalate
Structural formula of dimethyl terephthalate Dimethylterephthalat.svg
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
3D model (JSmol)
AbbreviationsDMT
1107185
ChEBI
ChemSpider
ECHA InfoCard 100.004.011 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 204-411-8
MeSH Dimethyl+4-phthalate
PubChem CID
  • 8441
  • 12241382  (2H4)
RTECS number
  • WZ1225000
UNII
  • InChI=1S/C10H10O4/c1-13-9(11)7-3-5-8(6-4-7)10(12)14-2/h3-6H,1-2H3 Yes check.svgY
    Key: WOZVHXUHUFLZGK-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C10H10O4/c1-13-9(11)7-3-5-8(6-4-7)10(12)14-2/h3-6H,1-2H3
    Key: WOZVHXUHUFLZGK-UHFFFAOYSA-N
  • COC(=O)C1=CC=C(C=C1)C(=O)OC
  • O=C(OC)c1ccc(cc1)C(=O)OC
Properties
C10H10O4
Molar mass 194.186 g·mol−1
Appearancewhite 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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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]

Contents

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 para-xylene via methyl para-toluate (PT). [1]

Dimethyl terephthalate by the Witten process

Structure of monomethyl terephthalate Monomethyl terephthalate.png
Structure of monomethyl terephthalate

Oxidation of methyl p-toluate followed by esterification also yields dimethyl terephthalate (DMT) as shown in the below reaction: [1]

Esterification of terephthalic acid with methanol.svg

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 + 2 CH3OH → C10H10O4 + 2 H2O

in the presence of o-xylene at 250–300 °C (482–572 °F).

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[ clarification needed ], 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.[ why? ]

Hazards

DMT is not directly dangerous to humans, but it is harmful to aquatic organisms, so environmental releases are avoided. It is flammable and the dust may form explosive mixtures with air. [3]

References

  1. 1 2 3 J. Sheehan, Richard. "Terephthalic Acid, Dimethyl Terephthalate, and Isophthalic Acid". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a26_193. ISBN   978-3-527-30673-2.
  2. "Dimethyl Terephthalate (DMT)". 2013-05-02. Archived from the original on 2017-10-07. Retrieved 2015-03-05.
  3. International Chemical Safety Card 0262