Dimethyl terephthalate (DMT) is an organic compound

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 with the formula C₆H₄(CO₂CH₃)₂. It is the diester

Ester

Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

 formed from terephthalic acid

Terephthalic acid

Terephthalic acid is the organic compound with formula C6H42. This colourless solid is a commodity chemical, used principally as a precursor to the polyester PET, used to make clothing and plastic bottles. Several billion kilograms are produced annually...

 and methanol

Methanol

Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

. It is a white solid that melts to give a distillable colourless liquid.

Production

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

P-Xylene

p-Xylene is an aromatic hydrocarbon, based on benzene with two methyl substituents. The “p” stands for para, identifying the location of the methyl groups as across from one another....

 via methylp-toluate.

Use

DMT is used in the production of polyester

Polyester

Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...

s, including polyethylene terephthalate

Polyethylene terephthalate

Polyethylene terephthalate , commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination...

 (PET) and polytrimethylene terephthalate

Polytrimethylene terephthalate

Polytrimethylene terephthalate, or PTT, is a polymer synthesized and patented in 1941. It is produced by a method called condensation polymerization or transesterification. The two monomer units used in producing this polymer are: 1,3-propanediol and terephthalic acid or dimethyl terephthalate...

. It consists of benzene

Benzene

Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

 substituted with carboxymethyl groups (CO₂CH₃) at the 1 and 4 positions. Because DMT is volatile, it is an intermediate is some schemes for the recyclic of PET, e.g. from plastic bottle

Plastic bottle

A plastic bottle is a bottle constructed of plastic, with a neck that is narrower than its real body and an opening at the top. The mouth of the bottle is normally sealed with a plastic bottle cap. Plastic bottles are typically used to store liquids such as water, soft drinks, motor oil, cooking...

s.

Hydrogenation of DMT affords the diol cyclohexanedimethanol

Cyclohexanedimethanol

Cyclohexanedimethanol is an organic compound with formula C6H102. It is a colorless low-melting solid used in the production of polyester resins. Commercial samples consist of a mixture of cis and trans isomers, as seen for other disubstituted derivatives of cyclohexane.-Production:CHDM is...

, which is a useful monomer.

External links

• http://www.inchem.org/documents/icsc/icsc/eics0262.htm