4-Aminophenol
[CAS# 123-30-8]

Identification

• Classification: Organic raw materials >> Alcohols, phenols, phenolic compounds and derivatives >> Phenol and its halogenated, sulfonated, nitrated or nitrosated derivatives
• Name: 4-Aminophenol
• Synonyms: 4-Amino-1-hydroxybenzene; 4-Hydroxyaniline
• Molecular Formula: C₆H₇NO
• Molecular Weight: 109.13
• CAS Registry Number: 123-30-8
• EC Number: 204-616-2
• SMILES: C1=CC(=CC=C1N)O

Properties

• Melting point: 188 °C
• Boiling point: 284 °C
• Flash point: 189 °C
• Water solubility: 1.5 g/100 mL (20 °C)

Safety Data

• Hazard Symbols: GHS07;GHS08;GHS09 Danger
• Risk Statements: H302+H332-H302-H317-H332-H341-H373-H400-H410
• Safety Statements: P203-P260-P261-P264-P270-P271-P272-P273-P280-P301+P317-P302+P352-P304+P340-P317-P318-P319-P321-P330-P333+P317-P362+P364-P391-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H332
Germ cell mutagenicity	Muta.	2	H341
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Skin sensitization	Skin Sens.	1	H317
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H410
Germ cell mutagenicity	Muta.	2	H340
Acute toxicity	Acute Tox.	1	H310

• Transport Information: UN 2512

Discovery and Applications

4-Aminophenol (C6H4(NH2)OH) is an organic compound that plays a key role in the pharmaceutical and dye industries. 4-Aminophenol has two functional groups (amino and hydroxyl groups) and is a versatile intermediate in the synthesis of various chemicals.

4-Aminophenol was discovered in the late 19th century and was originally isolated from the reduction of p-nitrophenol. It is a white to light brown crystalline solid with moderate solubility in water. Its chemical structure enables it to participate in a variety of reactions, making it an essential component in synthetic chemistry.

The benzene ring of 4-aminophenol is substituted at the para position by an amino group (-NH2) and a hydroxyl group (-OH). This unique structure enables it to undergo typical reactions of phenols and amines, such as nucleophilic substitution and electrophilic addition, making it highly reactive and versatile.

The most prominent application of 4-aminophenol is the synthesis of the widely used analgesic and antipyretic drug acetaminophen. During this process, 4-aminophenol is acetylated with acetic anhydride to produce acetaminophen, an essential drug for pain relief and fever reduction. 4-Aminophenol is an intermediate in the synthesis of a variety of drugs, including some antimalarials and sulfonamide antibiotics, demonstrating its versatility in medicinal chemistry.

In the dye industry, 4-aminophenol is used as a precursor in the production of permanent hair dyes. It reacts with other chemicals to form colored compounds that give hair a lasting color. 4-Aminophenol is also used to make azo dyes, which are used in the textile industry to dye fabrics, providing vibrant and stable colors.

Historically, 4-aminophenol was used as a developer for black-and-white photography. It reduces silver halides to metallic silver, resulting in photographic images. Although largely replaced by modern digital technology, its role in traditional photographic development remains a noteworthy application.

While 4-aminophenol is valuable in a variety of industrial applications, it must be handled with care. Contact can cause skin and eye irritation, and prolonged exposure may lead to more serious health effects. Proper safety measures, such as wearing gloves and goggles, are essential to reduce the risk.

References

1979. Microsomal mediated metabolism of dialkylaryltriazenes. II. Isolation and identification of metabolites of 3,3-dimethyl-1-phenyltriazene. Journal of Cancer Research and Clinical Oncology.
DOI: 10.1007/bf00964576

2008. New Analgesics Synthetically Derived from the Paracetamol Metabolite N-(4-Hydroxyphenyl)-(5Z,8Z,11Z,14Z)-icosatetra-5,8,11,14-enamide. Journal of Medicinal Chemistry.
DOI: 10.1021/jm800807k

2010. p-Aminophenol-multiwall carbon nanotubes-TiO2 electrode as a sensor for simultaneous determination of penicillamine and uric acid. Colloids and surfaces. B, Biointerfaces.
DOI: 10.1016/j.colsurfb.2010.06.020