Table 1 Properties of PPD and PTD

Names and synonyms

para-Phenylenediamine (PPD)

para-Toluenediamine (PTD)

1,4-Benzenediamine

2-Methyl-para-phenylenediamine

1,4-Diaminobenzene

2,5-Diaminotoluene

4-Aminoaniline

2-Methyl-1,4-diaminobenzene

Structural formula

CAS number

106-50-3

95-75-5

Molecular mass (g · mol⁻¹)

108.14

122.19

Aggregate state (STP)

Solid (colorless or light red crystals)

Solid (light yellow crystals)

Melting point (°C)

139.7

64

Boiling point (°C)

267

273.7

Hazard symbols

Water solubility at 25 °C (g L⁻¹)

37.0

72.4

log K_OW

−0.36

0.16

LD₅₀ (oral, rat)

80 mg · kg⁻¹

102 mg · kg⁻¹

LD₅₀ (inhalation, rat)

0.92 mg/l/4 h

pK_a1

2.8 [27], 3.29 [28]

2.77

pK_a2

6.08 [28], 6.20 [27], 6.44 [29]

6.39