1,5-Naphthalenedisulfonic acid tetrahydrate
[CAS# 211366-30-2]

Identification

• Classification: Organic raw materials >> Hydrocarbon compounds and their derivatives >> Hydrocarbon sulfonate
• Name: 1,5-Naphthalenedisulfonic acid tetrahydrate
• Synonyms: Armstrong's acid
• Molecular Formula: C₁₀H₈O₆S₂^.4(H₂O)
• Molecular Weight: 360.35
• CAS Registry Number: 211366-30-2
• EC Number: 678-302-2
• SMILES: C1=CC2=C(C=CC=C2S(=O)(=O)O)C(=C1)S(=O)(=O)O.O.O.O.O

Safety Data

• Hazard Symbols: GHS05 Danger
• Hazard Statements: H314
• Precautionary Statements: P260-P264-P280-P301+P330+P331-P302+P361+P354-P304+P340-P305+P354+P338-P316-P321-P363-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin corrosion	Skin Corr.	1B	H314
Serious eye damage	Eye Dam.	1	H318
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Skin corrosion	Skin Corr.	1C	H314

• Transport Information: UN 2585

Discovory and Applicatios

1,5-Naphthalenedisulfonic acid tetrahydrate is an organic compound derived from naphthalene, characterized by the presence of two sulfonic acid groups (-SO₃H) at the 1- and 5-positions on the aromatic system, and crystallized with four molecules of water. This substance belongs to the class of disulfonated aromatic compounds, which have been extensively studied and utilized in industrial chemistry, particularly for their solubility-enhancing and ion-exchange properties.

The discovery of 1,5-naphthalenedisulfonic acid dates back to the 19th century during the systematic investigation of sulfonation reactions of aromatic hydrocarbons. Researchers such as August Kekulé and other chemists of the era explored the reactions of sulfuric acid with naphthalene to understand substitution patterns and reaction mechanisms. The disulfonation of naphthalene under controlled conditions leads to several isomeric disulfonic acids, among which the 1,5-isomer is one of the prominent products. Crystallization from aqueous solutions often results in the formation of a tetrahydrate, stabilizing the compound in a solid form suitable for further manipulation and application.

In terms of application, 1,5-naphthalenedisulfonic acid tetrahydrate plays an important role in the synthesis of dyes, pigments, and optical brighteners. The sulfonic acid groups increase the water solubility of naphthalene derivatives, making them ideal intermediates in the preparation of azo dyes. These dyes are formed through diazotization and subsequent coupling reactions, where water solubility is critical for reaction efficiency and product application in textile and paper industries.

Beyond dye synthesis, 1,5-naphthalenedisulfonic acid has found use as a precursor for the preparation of sulfonated polymers and ion-exchange resins. The introduction of sulfonic acid functionalities imparts strong proton-donating ability to polymeric materials, making them effective as cation-exchange resins used in water treatment, chemical separations, and catalysis. The specific positioning of the sulfonic groups in the 1,5-disubstituted pattern provides predictable and reproducible properties to the resulting materials.

The acid is also employed in analytical chemistry as a standard substance or reagent in titrations involving basic compounds. Due to its strong acidity and high solubility, it provides reliable and reproducible results in acid-base quantifications. Furthermore, it has been investigated for potential roles in supramolecular chemistry, where its multiple sulfonic acid groups can participate in hydrogen bonding and ionic interactions to construct organized assemblies and networks.

From a structural point of view, the tetrahydrate form of 1,5-naphthalenedisulfonic acid benefits from the stabilization provided by hydrogen bonding with water molecules. This hydration state influences not only the physical properties such as melting point and solubility but also the behavior of the compound in crystallization and formulation processes.

Industrial preparation of 1,5-naphthalenedisulfonic acid typically involves the controlled sulfonation of naphthalene using concentrated or fuming sulfuric acid, sometimes with the aid of catalysts or under specific temperature regimes to favor the 1,5-isomer over other possible substitution patterns. Subsequent crystallization from water leads to the isolation of the tetrahydrate form, which is then purified for use in various chemical manufacturing processes.

Handling and storage of 1,5-naphthalenedisulfonic acid tetrahydrate require standard precautions suitable for acidic and hygroscopic materials. Although it is not considered highly hazardous, prolonged exposure or improper handling can cause irritation to the skin, eyes, and respiratory tract, necessitating the use of appropriate personal protective equipment and storage in tightly closed containers under dry conditions.

The well-established properties and diverse applications of 1,5-naphthalenedisulfonic acid tetrahydrate continue to support its significance in both academic research and industrial practice, contributing to advancements in material science, dye chemistry, and environmental technology.

References

1994. Peptide crystal growth via sulfonate salt formation: The structure of bis-glycylglycine-1,5-naphthalenedisulfonate hydrate. International Journal of Peptide Research and Therapeutics, 44(6).
DOI: 10.1007/bf00128530

2014. Crystal and Molecular Structure of Two Proton Transfer Compounds from Quinolin-8-ol, 4-nitro-phthalic Acid, and 1,5-Naphthalenedisulfonic Acid. Journal of Chemical Crystallography, 44(8).
DOI: 10.1007/s10870-014-0534-2

2015. Crystal and Molecular Structures of Three Salts from Aliphatic Amines (2,4-Dichlorophenoxy)-acetic acid, 4-Nitrophthalic Acid, and 1,5-Naphthalenedisulfonic Acid. Journal of Chemical Crystallography, 45(10-12).
DOI: 10.1007/s10870-015-0619-6