4-Aminobenzoic acid
[CAS# 150-13-0]

Identification

• Classification: Organic raw materials >> Carboxylic compounds and derivatives >> Halogenation, sulfonation, nitration or nitrosation of carboxylic acids
• Name: 4-Aminobenzoic acid
• Synonyms: 1-Amino-4-carboxybenzene; p-Aminobenzoic acid; PABA
• Molecular Formula: C₇H₇NO₂
• Molecular Weight: 137.14
• Protein Sequence: X
• CAS Registry Number: 150-13-0
• EC Number: 205-753-0
• SMILES: C1=CC(=CC=C1C(=O)O)N

Properties

• Density: 1.374
• Melting point: 186-189 °C
• Water solubility: 4.7 g/L (20 °C)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H317-H319-H335-H412
• Safety Statements: P261-P264-P264+P265-P271-P272-P273-P280-P302+P352-P304+P340-P305+P351+P338-P319-P321-P332+P317-P333+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Skin sensitization	Skin Sens.	1	H317
Acute toxicity	Acute Tox.	4	H302
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H312
Specific target organ toxicity - single exposure	STOT SE	3	H336
Eye irritation	Eye Irrit.	2A	H319

Discovery and Applications

4-Aminobenzoic acid, commonly known as PABA, is an aromatic compound with the formula C7H7NO2. It is a benzoic acid derivative where an amino group is substituted at the para position relative to the carboxyl group. This simple yet versatile molecule has found diverse applications in various scientific and industrial fields.

The discovery of 4-aminobenzoic acid dates back to the early 20th century, when it was identified as a key component in the synthesis of folic acid. Its structural simplicity combined with the presence of both an amino and a carboxyl group makes it a useful intermediate in organic synthesis. The compound is derived from benzoic acid by introducing an amino group through a nitration and reduction process.

In terms of applications, 4-aminobenzoic acid plays a crucial role in the field of medicinal chemistry. It is a precursor to folic acid (vitamin B9), which is essential for various biological functions, including DNA synthesis and repair. Folic acid is a vital nutrient for cellular division and growth, making 4-aminobenzoic acid an important substance in the synthesis of this essential vitamin.

Another significant application of 4-aminobenzoic acid is in the production of sunscreen agents. The compound has been used as a component in some sunscreens due to its ability to absorb ultraviolet (UV) light, thereby protecting the skin from harmful UV radiation. Although less commonly used today due to the development of more effective sunscreen agents, PABA played a foundational role in the early days of sunscreen formulation.

Additionally, 4-aminobenzoic acid is utilized in the synthesis of dyes and pharmaceuticals. It is employed as a building block in the manufacture of azo dyes, which are widely used in textiles and inks. The compound's amino and carboxyl groups facilitate various chemical reactions, making it a valuable starting material for the creation of complex dye structures.

In the pharmaceutical industry, 4-aminobenzoic acid is explored for its potential therapeutic properties. It has been investigated for its role in the treatment of certain skin conditions and in drug formulations that require the presence of an amino benzoic acid moiety. Its ability to modify the activity of other drugs and its role in biochemical pathways make it a subject of ongoing research.

Moreover, 4-aminobenzoic acid serves as a reference standard in chemical analysis and as a reagent in various chemical reactions. Its presence in chemical libraries and its use in analytical methods highlight its importance in research and quality control processes.

Overall, 4-aminobenzoic acid is a foundational chemical compound with a range of applications spanning from medicinal chemistry to industrial processes. Its role in the synthesis of folic acid, its use in sunscreens, and its applications in dye production underscore its versatility and importance in both scientific research and practical applications.

References

2025. New Ti/CNT/CNT-Ce-PbO2 anode synergy peroxymonosulfate activation for efficiently electrocatalytic degradation of p-aminobenzoic acid. Environmental Research, 264, 120383.
DOI: 10.1016/j.envres.2024.120383

2024. Characteristics and functional bacteria of an efficient benzocaine-mineralizing bacterial consortium. Journal of Hazardous Materials, 480, 135773.
DOI: 10.1016/j.jhazmat.2024.135773

2024. Electrochemical immunosensing of Crohn's disease biomarkers using diazonium salt-grafted crystalline nanocellulose/carbon nanotube-modified electrodes. Microchimica Acta, 191(12), 714.
DOI: 10.1007/s00604-024-06868-2