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Cyclopentadiene

Names Preferred IUPAC nameCyclopenta-1,3-dieneOther names 1,3-CyclopentadienePyropentyleneIdentifiers CAS Number542-92-73D model (JSmol)Interactive imageAbbreviations CPD, HCp Beilstein Reference471171 ChEBICHEBI:30664ChemSpider7330ECHA InfoCard100.008.033EC Number208-835-4Gmelin Reference1311 MeSH1,3-cyclopentadienePubChemCID7612RTECS numberGY1000000UNII5DFH9434HFCompTox Dashboard(EPA)DTXSID0027191InChIInChI=1S/C5H6/c1-2-4-5-3-1/h1-4H,5H2Key: ZSWFCLXCOIISFI-UHFFFAOYSA-NInChI=1/C5H6/c1-2-4-5-3-1/h1-4H,5H2Key: ZSWFCLXCOIISFI-UHFFFAOYAISMILESC1C=CC=C1Properties Chemical formulaC5H6Molar mass66.103 g·mol Appearance Colourless liquid Odorirritating, terpene-like Density0.802 g/cm Melting point−90 °C; −130 °F; 183 K Boiling point39 to 43 °C; 102 to 109 °F; 312 to 316 K Solubility in waterinsoluble Vapor pressure400 mmHg (53 kPa) Acidity (pKa) 16 Conjugate baseCyclopentadienyl anionMagnetic susceptibility (χ)−44.5×10 cm/molRefractive index (nD)1.44 (at 20 °C) Structure Molecular shapePlanar Dipole moment0.419 DThermochemistry Heat capacity(C)115.3 J/(mol·K) Std molarentropy(S298)182.7 J/(mol·K) Std enthalpy offormation(ΔfH298)105.9 kJ/mol Hazards NFPA 704 (fire diamond) 230Flash point25 °C (77 °F; 298 K) Autoignitiontemperature640 °C (1,184 °F; 913 K) Lethal dose or concentration (LD, LC): LC50 (median concentration)14,182 ppm (rat, 2 h)5091 ppm (mouse, 2 h) NIOSH (US health exposure limits): PEL (Permissible)TWA 75 ppm (200 mg/m) REL (Recommended)TWA 75 ppm (200 mg/m) IDLH (Immediate danger)750 ppm Related compounds Related hydrocarbonsBenzeneCyclobutadieneCyclopenteneRelated compoundsDicyclopentadieneExcept where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).Nverify ( ?)

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