The key difference between isophthalic acid and terephthalic acid is that isophthalic acid has its two carboxylic acid groups separated from one carbon atom. Whereas, terephthalic acid has its two carboxylic acid groups separated from two carbon atoms.
Isophthalic acid and terephthalic acid are important organic compounds which are aromatic carboxylic acids containing two –COOH groups per molecule.
CONTENTS
1. Overview and Key Difference
2. What is Isophthalic Acid
3. What is Terephthalic Acid
4. Side by Side Comparison – Isophthalic Acid vs Terephthalic Acid in Tabular Form
5. Summary
What is Isophthalic Acid?
Isophthalic acid is an aromatic organic compound having the chemical formula C6H4(CO2H)2 and meta conformation. The molar mass of this compound is 166 g/mol. Also, it occurs as a colourless solid compound. Isophthalic acid is an isomer of phthalic acid and terephthalic acid.
When considering the production process, we can produce isophthalic acid via oxidizing meta-xylene in the presence of oxygen. This is an industrial-scale production process. Also, this process requires a catalyst such as cobalt- manganese catalyst. However, we can produce isophthalic acid in the laboratory via fusion of potassium meta-sulfobenzoate with potassium formate in the presence of chromic acid.
Moreover, isophthalic acid is an aromatic compound. And, it is composed of a benzene ring with two carboxylic acid groups substituted to the ring. Here, one carboxylic acid group is in the meta position compared to the other carboxylic acid group. Therefore, the two functional groups are separated from each other from one carbon atom of the ring.
Figure 01: The Chemical Structure of Isophthalic Acid
Besides, isophthalic acid is insoluble in water. The major use of this compound is in the production of PET or polyethylene terephthalate polymer material which is useful as a resin. In addition, we can use it for the production of unsaturated polyester resin or UPR.
What is Terephthalic Acid?
Terephthalic acid is an aromatic organic compound having the chemical formula C6H4(CO2H)2 and para conformation. It occurs as a white crystalline powder. Also, it is insoluble in water but soluble in polar organic solvents.
When considering the production of terephthalic acid, the major process is Amoco process. Here, the acid is produced via oxidation of p-xylene in the presence of oxygen in the air. The reaction is as follows:
Figure 02: The Production Process of Terephthalic Acid
Besides, concerning the applications, there are many uses of terephthalic acid. For example, it is useful as a precursor for PET production (polyethylene terephthalate), used in paints as a carrier compound, as a raw material for certain drugs in pharmaceutical applications, as a filler in certain military smoke grenades, etc.
What is the Difference Between Isophthalic Acid and Terephthalic Acid?
The key difference between isophthalic acid and terephthalic acid is that isophthalic acid has its two carboxylic acid groups separated from one carbon atom. Whereas, terephthalic acid has its two carboxylic acid groups separated from two carbon atoms. Furthermore, isophthalic acid is an aromatic organic compound having the chemical formula C6H4(CO2H)2 and meta conformation, while terephthalic acid is an aromatic organic compound having the chemical formula C6H4(CO2H)2 and para conformation.
Below infographic shows a more detailed tabulation of the difference between isophthalic acid and terephthalic acid.
Summary – Isophthalic Acid vs Terephthalic Acid
Isophthalic acid and terephthalic acid are important organic compounds which are aromatic carboxylic acids containing two –COOH groups per molecule. The key difference between isophthalic acid and terephthalic acid is that isophthalic acid has its two carboxylic acid groups separated from one carbon atom. But, terephthalic acid has its two carboxylic acid groups separated from two carbon atoms.
Reference:
1. “Isophthalic Acid.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
2. “Terephthalic Acid.” Terephthalic Acid – an Overview | ScienceDirect Topics, Available here.
Image Courtesy:
1. “Isophthalic-acid-2D-skeletal” (Public Domain) via Commons Wikimedia
2. “Oxidation p xylene” By Simon.KR – Own work (CC BY-SA 3.0) via Commons Wikimedia