1. Basic Identification Information

Parameter	English Specification/Value
IUPAC Name	4-Aminophenol (also: p-Aminophenol; 4-Hydroxyaniline)
Common Name(s)	4-Aminophenol; p-Aminophenol (PAP); 4-Hydroxyaniline; para-Aminophenol; C.I. 76500 (Color Index)
CAS Registry Number	123-30-8
EC/EINECS Number	204-616-2
Molecular Formula	C₆H₇NO
Molecular Weight	109.13 g/mol
Chemical Class	Aminophenol derivative; oxidative hair dye coupler; pharmaceutical intermediate; dye precursor
Related Compound	Acetaminophen (Paracetamol, CAS 103-90-2) (acetylated derivative; analgesic/antipyretic drug with low cosmetic use risk)

2. Physicochemical Properties

Property Category	Specific Parameter	Specification/Value
Structural Features	Functional Groups	Amino group (-NH₂) at C4; hydroxyl group (-OH) at C1 on benzene ring (para-substitution; enables intramolecular hydrogen bonding and azo dye coupling)
Physical Appearance	State & Color	White to pale gray crystalline powder; turns brown/black rapidly on air/light exposure (oxidation to quinone); faint phenolic/amine odor
	Melting Point	189–190 °C (lit.; decomposes slightly above melting point)
	Boiling Point	284 °C (lit.; sublimes at atmospheric pressure; decomposes >300 °C)
	Density (25 °C)	1.29 g/cm³ (crystalline form)