What is the Difference Between Alpha and Beta Naphthol

The key difference between alpha and beta naphthol is that alpha naphthol has a hydroxyl group at the 1^st carbon atom that is adjacent to the ring structure, whereas beta naphthol has a hydroxyl group at the 2^nd carbon atom from the ring structure.

Alpha and beta naphthol are structural isomers of each other. Alpha naphthol is chemically named as 1-naphthol or naphthalen-1-ol, while beta naphthol is chemically named as naphthalen-2-ol. These compounds are useful as biomarkers in livestock and humans who are exposed to polycyclic aromatic hydrocarbons.

CONTENTS

1. Overview and Key Difference
2. What is Alpha Naphthol 
3. What is Beta Naphthol 
4. Similarities Between Alpha and Beta Naphthol
5. Alpha vs Beta Naphthol in Tabular Form
6. Summary – Alpha vs Beta Naphthol 

What is Alpha Naphthol?

Alpha naphthol is an organic compound having the chemical formula C10H7OH. In this compound, a hydroxyl group is attached to the carbon atom that is adjacent to the neighbouring ring structure. It is a fluorescent organic compound. It is also known as 1-naphthol or naphthalen-1-ol. It is a structural isomer of beta naphthol. These two isomers differ from each other depending on the location of the -OH group.

Generally, naphthol compounds are naphthalene homologues compounds of phenol. However, the hydroxyl group is more reactive compared to the corresponding phenols. In a naphthol molecule, there are two ring structures attached to each other. One of these ring structures contains a substituted hydroxyl group. Alpha naphthol compound appears as a colourless or white solid that is commercially available in strong colours.

Alpha naphthol can be produced in two major ways. The most common way is the nitration of naphthalene to form 1-nitronaphthalene. Thereafter, it is hydrogenated to the corresponding amine compound. Then we can do the hydrolysis to get the desired naphthol product. The second method is hydrogenation of naphthalene to tetralin, followed by a dehydrogenation reaction.

The applications of alpha naphthol include its use in Molisch’s test, rapid furfural test, Sakaguchi test, and Voges-Proskauer test, as a precursor to different insecticides such as carbonyl and pharmaceutical such as nadolol, etc.

What is Beta Naphthol?

Beta naphthol is an organic compound having the chemical formula C10H7OH. In this compound, a hydroxyl group is attached to the 2^nd carbon atom from the neighbouring ring structure. It is chemically named 2-naphthol or naphthalen-2-ol. Beta naphthol is a fluorescent colourless crystalline substance. This substance is different from alpha naphthol according to the location of the hydroxyl group.

Beta naphthol is important as an intermediate in the production of dyes and other compounds. It is available as a colourless crystalline solid that can be harmful when inhaled or swallowed.

When considering the production of beta naphthol, it is produced through a process with two steps; the sulfonation of naphthalene in sulfuric acid (followed by the cleavage of molten sodium hydroxide) and the neutralization reaction.

What are the Similarities Between Alpha and Beta Naphthol?

1. Alpha and Beta Naphthol are structural isomers.
2. Both are useful as biomarkers.
3. They are soluble in simple alcohols, ethers, and chloroform.

What is the Difference Between Alpha and Beta Naphthol?

Alpha and beta naphthol are structural isomers of each other. The key difference between alpha and beta naphthol is that alpha naphthol has a hydroxyl group at the 1^st carbon atom that is adjacent to the ring structure, whereas beta naphthol has a hydroxyl group at the 2^nd carbon atom from the ring structure.

The below infographic lists the differences between alpha and beta naphthol in tabular form for side by side comparison.

Summary – Alpha vs Beta Naphthol

Alpha and beta naphthol are structural isomers of each other. The key difference between alpha and beta naphthol is that alpha naphthol has a hydroxyl group at the 1^st carbon atom that is adjacent to the ring structure, whereas beta naphthol has a hydroxyl group at the 2^nd carbon atom from the ring structure.

Reference:

1. “2-Naphthol.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine.

Image Courtesy:

1. “Alpha-Naphthol” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
2. “Beta-Naphthol” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia