1. Basic Identification Information

Parameter	English Specification/Value
IUPAC Name	Benzene-1,4-diamine (also: 1,4-Diaminobenzene)
Common Name(s)	p-Phenylenediamine (PPD); 1,4-Phenylenediamine; p-Diaminobenzene; C.I. 76060 (Color Index)
CAS Registry Number	106-50-3
EC/EINECS Number	203-404-7
Molecular Formula	C₆H₈N₂
Molecular Weight	108.14 g/mol
Chemical Class	Aromatic diamine; oxidative hair dye primary base; dye/polymer intermediate; photographic developer
Related Compound	2-Nitrobenzene-1,4-diamine (p-NPPD, CAS 99-56-9) (nitro-substituted analog; coupler for deep brown/black shades with lower sensitization risk than PPD)

2. Physicochemical Properties

Property Category	Specific Parameter	Specification/Value
Structural Features	Functional Groups	Two primary amino groups (-NH₂) at C1/C4 positions of benzene ring (para-substitution; enables intramolecular hydrogen bonding and azo dye formation)
Physical Appearance	State & Color	White to pale purple crystalline powder; darkens to brown/black on exposure to air/light (oxidation); faint amine-like odor
	Melting Point	145–147 °C (lit.)
	Boiling Point	267 °C (lit.; sublimes at atmospheric pressure; decomposes above 300 °C)
	Density (25 °C)	1.20 g/cm³ (crystalline form)
Solubility	Polar Solvents	Soluble in ethanol (1 g/2 mL), methanol, acetone, and dilute acids (forms diamine salts); moderately soluble in propylene glycol (1 g/15 mL)