What Is 2-Amino-3-hydroxybenzoic acid

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Last updated: April 15, 2026

Quick Answer: 2-Amino-3-hydroxybenzoic acid (CAS 364-72-3) is an organic compound with the molecular formula C7H7NO3, used primarily in research as an intermediate in dye and pharmaceutical synthesis. It features both amine and carboxylic acid functional groups, contributing to its reactivity in chemical processes.

Key Facts

2-Amino-3-hydroxybenzoic acid has the molecular formula C7H7NO3 and a molecular weight of 153.14 g/mol
It was first synthesized in the early 20th century during studies on aromatic amino acids
The compound has a melting point range of 188–192°C
It is sparingly soluble in cold water but more soluble in hot water and ethanol
Its CAS Registry Number is 364-72-3

Overview

2-Amino-3-hydroxybenzoic acid is a substituted benzoic acid derivative featuring both an amino group and a hydroxyl group on the aromatic ring. This arrangement gives the molecule unique chemical properties, making it valuable in specialized organic synthesis and biochemical research contexts.

The compound is not naturally abundant and is typically produced in laboratory settings for experimental use. Its dual functional groups allow for diverse reactivity, particularly in condensation and coupling reactions.

Chemical structure: The molecule consists of a benzene ring with a carboxylic acid at position 1, an amino group at position 2, and a hydroxyl group at position 3, forming a tri-substituted aromatic system.
Solubility: It exhibits limited solubility in cold water (0.5 g/L at 20°C) but dissolves more readily in heated solvents such as ethanol or methanol.
Melting point: The compound decomposes near 190°C, with reported melting ranges between 188–192°C, indicating thermal instability at higher temperatures.
Stability: It is sensitive to light and air, requiring storage under inert atmosphere at -20°C to prevent oxidation and degradation over time.
Synthesis: Typically prepared via nitration of 3-hydroxybenzoic acid followed by catalytic reduction of the nitro group to an amine using hydrogen and palladium on carbon.

Chemical Properties and Reactivity

Understanding how 2-amino-3-hydroxybenzoic acid behaves in chemical environments is essential for its application in synthesis and material science.

Acid-base behavior: The carboxylic acid group has a pKa of ~4.2, allowing deprotonation in mildly basic conditions, while the amino group can be protonated below pH 8.
Tautomerism: The proximity of the hydroxyl and amino groups enables intramolecular hydrogen bonding, potentially stabilizing zwitterionic or quinoid forms in solution.
Reactivity: The amino group readily undergoes acylation or diazotization, useful for generating dyes or heterocyclic compounds in medicinal chemistry.
Chelation ability: It can act as a bidentate ligand, forming complexes with transition metals like Cu(II) or Fe(III) due to its oxygen and nitrogen donor atoms.
UV absorption: Exhibits strong absorbance in the 270–290 nm range, making it detectable by HPLC with UV detection in analytical workflows.
Derivatization: Commonly converted into esters or amides to improve solubility or stability for use in peptide-like frameworks or fluorescent probes.

Comparison at a Glance

Below is a comparison of 2-amino-3-hydroxybenzoic acid with structurally related aromatic acids:

Compound	Molecular Weight (g/mol)	Melting Point (°C)	Solubility in Water	Primary Use
2-Amino-3-hydroxybenzoic acid	153.14	188–192	Sparingly soluble	Chemical intermediate
Anthranilic acid	137.14	145–148	Moderately soluble	Dye and pharmaceutical precursor
3-Aminobenzoic acid	137.14	174–176	Soluble	Agrochemical synthesis
Salicylic acid	138.12	158–161	0.2 g/100mL	Medicinal and cosmetic applications
2,3-Dihydroxybenzoic acid	154.12	153–155	0.4 g/100mL	Iron chelation studies

The data highlights that 2-amino-3-hydroxybenzoic acid has a higher melting point than most analogs, likely due to stronger intermolecular hydrogen bonding. Its unique substitution pattern makes it less common in industrial applications but valuable in niche research areas such as sensor development and coordination chemistry.

Why It Matters

Though not widely used in commercial products, 2-amino-3-hydroxybenzoic acid holds significance in academic and industrial research due to its functional versatility.

Pharmaceutical research: Serves as a scaffold for developing novel antibacterial or anti-inflammatory agents through structural modification.
Dye synthesis: Used in the preparation of azo dyes via diazotization, contributing to colorant chemistry.
Coordination chemistry: Its ability to bind metal ions supports applications in metal sensors or catalysts.
Organic intermediates: Enables the construction of more complex heterocycles like benzoxazoles or quinazolines.
Environmental impact: Biodegradability studies show it breaks down within 28 days in aerobic conditions, reducing ecological risk.
Safety profile: Classified as irritant to skin and eyes (GHS Category 2), requiring careful handling in lab settings.

As synthetic methodologies evolve, compounds like 2-amino-3-hydroxybenzoic acid may find expanded roles in green chemistry and functional materials, underscoring the importance of continued study.