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Isophthalic Acid vs. Terephthalic Acid: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on January 11, 2024
Isophthalic acid is a benzene dicarboxylic acid with carboxyl groups at the 1,3-positions, while terephthalic acid has carboxyl groups at the 1,4-positions on the benzene ring.

Key Differences

Isophthalic acid has a chemical structure where the two carboxyl groups are positioned at the meta positions (1,3) of the benzene ring. Terephthalic acid’s carboxyl groups are at the para positions (1,4) on the benzene ring.
Isophthalic acid is known for its higher solubility in common organic solvents compared to terephthalic acid. Terephthalic acid, conversely, is less soluble in these solvents but is soluble in hot water.
Isophthalic acid is used in the production of high-performance polymers and resins, offering good resistance to water and chemicals. Terephthalic acid is primarily used in the manufacture of polyethylene terephthalate (PET) for making plastics and fibers.
Polymers made with isophthalic acid tend to have more flexible and impact-resistant properties. Terephthalic acid contributes to the production of polymers with high strength and rigidity.
Isophthalic acid is produced via the oxidation of meta-xylene. Terephthalic acid is produced mainly from the oxidation of p-xylene. The production processes influence their respective costs and availability.

Comparison Chart

Chemical Structure

Carboxyl groups at 1,3-positions on benzene ring
Carboxyl groups at 1,4-positions on benzene ring

Physical Properties

Higher solubility in organic solvents
Lower solubility in organic solvents, soluble in hot water

Industrial Application

High-performance polymers and resins
Manufacture of PET for plastics and fibers

Polymer Characteristics

Flexible, impact-resistant properties
High strength, rigidity

Production Method

Oxidation of meta-xylene
Oxidation of p-xylene

Isophthalic Acid and Terephthalic Acid Definitions

Isophthalic Acid

Enhances the flexibility of polymers.
Isophthalic acid is added to plastics to improve their impact resistance.

Terephthalic Acid

Produced mainly from the oxidation of p-xylene.
Terephthalic acid production largely relies on p-xylene as a starting material.

Isophthalic Acid

A benzene dicarboxylic acid with carboxyl groups at the meta positions.
Isophthalic acid is used in coatings due to its excellent water resistance.

Terephthalic Acid

A benzene dicarboxylic acid with carboxyl groups at the para positions.
Terephthalic acid is a primary ingredient in making PET bottles.

Isophthalic Acid

Used in high-performance polymer production.
Isophthalic acid is a key component in corrosion-resistant fiberglass.

Terephthalic Acid

Crucial for manufacturing strong and rigid polymers.
Terephthalic acid is used to produce durable polyester fibers.

Isophthalic Acid

Derived from the oxidation of meta-xylene.
The industrial production of isophthalic acid involves meta-xylene as a precursor.

Terephthalic Acid

Less soluble in organic solvents but soluble in hot water.
Terephthalic acid’s solubility properties affect its processing techniques.

Isophthalic Acid

Offers good solubility in organic solvents.
Isophthalic acid’s solubility makes it versatile in various chemical applications.

Terephthalic Acid

Widely used in plastic and fiber industries.
Terephthalic acid is integral to the production of consumer goods like clothing and packaging.


What’s the main use of terephthalic acid?

In manufacturing PET for plastics and fibers.

How is isophthalic acid produced?

Via the oxidation of meta-xylene.

Is isophthalic acid soluble in organic solvents?

Yes, it has good solubility in these solvents.

What is isophthalic acid?

A meta-positioned benzene dicarboxylic acid used in polymers and resins.

Can terephthalic acid dissolve in water?

It is soluble in hot water.

Is terephthalic acid eco-friendly?

It's used in recyclable PET products.

Why is terephthalic acid important in textiles?

It's used to make durable polyester fibers.

How does isophthalic acid impact polymer processing?

It improves processing characteristics like flexibility and chemical resistance.

What is terephthalic acid?

A para-positioned benzene dicarboxylic acid, essential in PET production.

Are isophthalic acid polymers flexible?

Yes, they are known for their flexibility and impact resistance.

How does terephthalic acid contribute to sustainability?

Through its use in recyclable plastics.

What’s a common application of isophthalic acid?

In high-performance coatings and fiberglass.

Does isophthalic acid resist chemicals?

Yes, it offers good chemical resistance.

What role does terephthalic acid play in packaging?

It's crucial in creating strong, lightweight plastic packaging.

What properties do terephthalic acid polymers have?

High strength and rigidity.

Are both acids derived from xylene?

Yes, but from different isomers: meta-xylene for isophthalic and p-xylene for terephthalic.

Can isophthalic acid be used in automotive parts?

Yes, particularly in corrosion-resistant parts.

Is terephthalic acid used in beverage containers?

Yes, in PET bottles for beverages.

What are the safety considerations for isophthalic acid?

Proper handling and storage due to its chemical nature.

Are there any biodegradable alternatives to these acids?

Research is ongoing for more sustainable, biodegradable alternatives.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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