What is the Difference Between Isophthalic Acid and Terephthalic Acid?

Isophthalic acid and terephthalic acid are both aromatic organic compounds and isomers of benzenedicarboxylic acid. The key difference between isophthalic acid and terephthalic acid lies in the position of their carboxylic acid groups:

• Isophthalic Acid: This compound has the chemical formula C6H4(CO2H)2 and is also known as meta-benzenedicarboxylic acid. Its two carboxylic acid groups are separated by a single carbon atom. Isophthalic acid is primarily used in the production of polyethylene isophthalate (PEI), a type of polyester.
• Terephthalic Acid: This compound has the chemical formula C6H4(CO2H)2 and is also known as para-benzenedicarboxylic acid. Its two carboxylic acid groups are separated by two carbon atoms. Terephthalic acid is used as a precursor for polyethylene terephthalate (PET) production, which is used in packaging, textiles, and other applications.

Furthermore, the acidity of these compounds varies:

1. Phthalic acid (ortho-phthalic acid)
2. Isophthalic acid (meta-phthalic acid)
3. Terephthalic acid (para-phthalic acid)

The difference in acidity is due to the position of the carboxylic acid groups and their influence on the stability of the conjugate base.

Comparative Table: Isophthalic Acid vs Terephthalic Acid

Isophthalic acid and terephthalic acid are both aromatic organic compounds with the chemical formula C6H4(CO2H)2, but they have different structures and properties. Here is a table summarizing the differences between isophthalic acid and terephthalic acid:

Isophthalic acid has its two carboxylic acid groups connected by one carbon atom, while terephthalic acid has its two carboxylic acid groups separated by two carbon atoms. The key difference between these two compounds is their structure, which influences their properties and applications.