Pyrrole

C₄H₅NMolar mass67.091 g·mol Appearance colorless volatile liquid Density0.967 g cm Melting point−23 °C (−9 °F; 250 K) Boiling point129 to 131 °C (264 to 268 °F; 402 to 404 K) Vapor pressure7 mmHg at 23 °C Acidity (pK_a) 17.5 (for the N−H proton) Basicity (pK_b) 13.6 (pK_a 0.4 for C.A.)

Magnetic susceptibility (χ)

−47.6×10 cm molViscosity0.001225 Pa s Thermochemistry

Heat capacity(C)

1.903 J K mol

Std enthalpy of
formation(Δ_fH₂₉₈)

108.2 kJ mol (gas)

Std enthalpy of
combustion(Δ_cH₂₉₈)

2242 kJ mol Hazards NFPA 704 (fire diamond)

2

0

Flash point33.33 °C (91.99 °F; 306.48 K)

Autoignition
temperature

550 °C (1,022 °F; 823 K) Explosive limits3.1–14.8% Safety data sheet (SDS) Chemical Safety DataRelated compounds

Related compounds

Phosphole, arsole, bismole, stibole

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

verify ( ?)

Pyrrole is a heterocyclic, aromatic, organic compound, a five-membered ring with the formulaC₄H₄NH. It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., N-methylpyrrole, C₄H₄NCH₃. Porphobilinogen, a trisubstituted pyrrole, is the biosynthetic precursor to many natural products such as heme.

Pyrroles are components of more complex macrocycles, including the porphyrinogens and products derived therefrom, including porphyrins of heme, the chlorins, bacteriochlorins, and chlorophylls.