1,4-Benzenedicarboxylic acid 1,4-dimethyl ester
[CAS 120-61-6]

Identification

• Classification: Chemical reagent >> Organic reagent >> Ester >> Methyl ester compound
• Name: 1,4-Benzenedicarboxylic acid 1,4-dimethyl ester
• Synonyms: Terephthalic acid dimethyl ester; DMT; Dimethyl 1,4-benzenedicarboxylate; Dimethyl p-benzenedicarboxylate; Dimethyl p-phthalate; Dimethyl terephthalate; Methyl 4-(carbomethoxy)benzoate; Methyl p-(methoxycarbonyl)benzoate; NSC 3503
• Molecular Formula: C₁₀H₁₀O₄
• Molecular Weight: 194.18
• CAS Registry Number: 120-61-6
• EC Number: 204-411-8
• SMILES: COC(=O)C1=CC=C(C=C1)C(=O)OC

Properties

• Density: 1.175
• Melting point: 139-140 °C
• Boiling point: 288 °C
• Flash point: 146 °C

Safety Data

• Hazard Symbols: GHS07;GHS08 Danger
• Risk Statements: H303-H316-H320-H372-H335-H401
• Safety Statements: P501-P273-P260-P270-P271-P264-P312-P337+P313-P305+P351+P338-P332+P313-P304+P340+P312-P403+P233-P405

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin sensitization	Skin Sens.	1	H317
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2A	H319
Skin irritation	Skin Irrit.	2	H315

Discovery and Applications

1,4-Dimethyl 1,4-benzenedicarboxylate, commonly known as dimethyl terephthalate (DMT), is a key chemical in the modern polymer industry. DMT was first synthesized in the 1940s during research on aromatic esters. Its structure consists of a benzene ring with two ester groups located in the para (1,4) positions, which provide the rigidity and symmetry required for polymer applications. Direct esterification of terephthalic acid with methanol produces DMT, making it a relatively readily available compound for industrial use.

The main application of DMT is in the production of PET. PET is widely used in the manufacture of plastic bottles, packaging materials, and synthetic fibers such as polyester. The polymerization process involves the reaction of DMT with ethylene glycol to form PET through transesterification and polycondensation reactions. The process produces a high-strength, versatile plastic that is essential for a variety of consumer and industrial products. PET's strength, clarity, and moisture resistance make it ideal for beverage bottles, food packaging, and synthetic fibers. DMT is also used in the manufacture of other thermoplastics and engineering resins, where the ester groups contribute to tensile strength, chemical resistance, and dimensional stability.

In addition to PET, DMT is used to produce polybutylene terephthalate (PBT), which is used in automotive parts and electrical insulators due to its high thermal stability. DMT is also used to produce liquid crystal polymers (LCP), which are used in electronic displays and components due to their excellent mechanical properties and heat resistance.

DMT is used to make engineering resins, films, and coatings, where its durability and transparency are its strengths. The ester groups in DMT promote strong intermolecular bonding, resulting in materials with excellent mechanical and thermal properties.

While DMT and its derivatives are essential to modern life, their widespread use raises environmental concerns. PET is not biodegradable, contributing to a serious plastic waste problem. However, recycling PET into new products is a sustainable solution, and ongoing research aims to enhance the recycling process and develop biodegradable alternatives.

References

1955. Macromolecular compounds. Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science.
DOI: 10.1007/bf01172125

2024. Synthesis and Properties Study of PESF-b-PBIT White Fluorescent Copolyesters. Arabian Journal for Science and Engineering.
DOI: 10.1007/s13369-024-09811-y

2024. Effects of Copolymer Structure on Enzyme-Catalyzed Polyester Recycling. Journal of Polymers and the Environment.
DOI: 10.1007/s10924-024-03223-7