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Cyclopentadiene

Cyclopentadiene
Names Preferred IUPAC name
Cyclopenta-1,3-diene
Other names
1,3-Cyclopentadiene
Pyropentylene
Identifiers
3D model (JSmol)
Abbreviations CPD, HCp 471171 ChEBI
ChemSpider
ECHA InfoCard100.008.033EC Number
  • 208-835-4
1311 MeSH1,3-cyclopentadiene
RTECS number
  • GY1000000
UNII
  • InChI=1S/C5H6/c1-2-4-5-3-1/h1-4H,5H2
    Key: ZSWFCLXCOIISFI-UHFFFAOYSA-N
  • InChI=1/C5H6/c1-2-4-5-3-1/h1-4H,5H2
    Key: ZSWFCLXCOIISFI-UHFFFAOYAI
  • C1C=CC=C1
Properties C5H6Molar 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 insoluble Vapor pressure400 mmHg (53 kPa) Acidity (pKa) 16 Conjugate baseCyclopentadienyl anion−44.5×10 cm/mol1.44 (at 20 °C) Structure Planar 0.419 DThermochemistry 115.3 J/(mol·K) 182.7 J/(mol·K) 105.9 kJ/mol Hazards NFPA 704 (fire diamond)
2
3
0
Flash point25 °C (77 °F; 298 K) 640 °C (1,184 °F; 913 K) Lethal dose or concentration (LD, LC): 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 hydrocarbons
Benzene
Cyclobutadiene
Cyclopentene
Related compounds
Dicyclopentadiene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Cyclopentadiene is an organic compound with the formula C5H6. It is often abbreviated CpH because the cyclopentadienyl anion is abbreviated Cp.

This colorless liquid has a strong and unpleasant odor. At room temperature, this cyclic dienedimerizes over the course of hours to give dicyclopentadiene via a Diels–Alder reaction. This dimer can be heated to induce thermal cracking and regenerate the monomer through a retro-Diels–Alder reaction

The compound is mainly used for the production of cyclopentene and its derivatives. It is popularly used as a precursor to the cyclopentadienyl anion (Cp), an important ligand in cyclopentadienyl complexes in organometallic chemistry.

Wikipedia source