What is the Difference Between Ortho and Para Nitrophenol

The key difference between ortho and para nitrophenol is that ortho nitrophenol molecule contains a -OH group and a -NO2 group attached to the 1 and 2 positions of the benzene ring, whereas para nitrophenol compound contains a -OH group attached to 1 and 4 positions of the benzene ring.

Ortho and para nitrophenol are aromatic organic compounds having -OH and -NO2 groups as substitutes in a benzene ring.

CONTENTS

1. Overview and Key Difference
2. What is Nitrophenol 
3. What is Ortho Nitrophenol 
4. What is Para Nitrophenol
5. Similarities – Ortho and Para Nitrophenol
6. Ortho vs Para Nitrophenol  in Tabular Form
7. Summary – Ortho vs Para Nitrophenol

What is Nitrophenol?

Nitrophenol is an organic compound having a benzene ring attached to a -OH group and -NO2 group to two carbon atoms of the benzene ring. Therefore, they have the chemical formula HOC₆H_5-x(NO₂)_x. These are the conjugate bases of nitrophenolates. The nitrophenol compounds are usually more acidic than phenols. Also, there are two types of nitrophenol: they are mono-nitrophenols and di-nitrophenols. Mono-nitrophenols contain one -NO2 group per molecule while there are two -NO2 groups in a di-nitrophenol molecule. We can name them as ortho, para or meta nitrophenols according to the position of the -OH group and -NO2 group in this molecule.

What is Ortho Nitrophenol?

Ortho nitrophenol is an organic compound having a benzene ring attached with a -OH group and a -NO2 group at 1 and 2 positions of the benzene ring. In other words, this compound has its substituted groups attached to the adjacent/neighboring carbon atoms. It occurs as a yellow crystalline solid.

Figure 01: The Chemical Structure of Ortho Nitrophenol

What is Para Nitrophenol?

Para nitrophenol is an organic compound having a benzene ring attached to a -OH group and a -NO2 group at 1 and 4 positions of the benzene ring. Therefore, the substituted groups are not attached to the adjacent carbon atoms.

Figure 02: The Chemical Structure of Para Nitrophenol

Para nitrophenol occurs as yellow crystals and it is important as a precursor to the rice herbicide fluorodifen, parathion (a pesticide), and also the paracetamol (a human analgesic).

What are the Similarities Between Ortho and Para Nitrophenol?

1. Both ortho and para nitrophenol are aromatic organic compounds.
2. They appear as yellow crystals.
3. Both compounds contain -OH and -NO2 groups as substitutes for benzene rings.

What is the Difference Between Ortho and Para Nitrophenol?

Ortho and para nitrophenol are isomers of nitrophenol organic molecules. Ortho nitrophenol is an organic compound having a benzene ring attached with a -OH group and a -NO2 group at 1 and 2 positions of the benzene ring, while para nitrophenol is an organic compound having a benzene ring attached with a -OH group and a -NO2 group at 1 and 4 positions of the benzene ring.

Therefore, the key difference between ortho and para nitrophenol is that ortho nitrophenol molecule contains -OH group and -NO2 group attached to the 1 and 2 positions of the benzene ring whereas para nitrophenol compound contains -OH group attached to 1 and 4 positions of the benzene ring. While para nitrophenol molecules have a symmetry axis, ortho nitrophenol molecules do not.

The following table summarizes the difference between ortho and para nitrophenol.

Summary – Ortho vs Para Nitrophenol

Ortho and para nitrophenol are isomers of nitrophenol organic molecules. The key difference between ortho and para nitrophenol is that ortho nitrophenol molecule contains -OH group and -NO2 group attached to the 1 and 2 positions of the benzene ring whereas para nitrophenol compound contains -OH group attached to 1 and 4 positions of the benzene ring.

Reference:

1. “4-Nitrophenol.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine.
2. “Nitrophenol.” An Overview | ScienceDirect Topics.
3. “2-Nitrophenol.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine.

Image Courtesy:

1. “O-Nitrophenol” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
2. “4-Nitrophenol acsv” By Calvero – Own work (Public Domain) via Commons Wikimedia

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