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1,3-Cyclopentadiene Basic information
1,3-Cyclopentadiene Chemical Properties
  • Melting point:-85°; mp 32.5°
  • Boiling point:bp760 41.5-42.0°
  • Density d40 0.8235; d410 0.8131; d420 0.8021; d425 0.7966; d430 0.7914
  • vapor pressure 381 at 20.6 °C, 735 at 40.6 °C, 1,380 at 60.9 °C (Stoeck and Roscher, 1977)
  • refractive index nD16 1.44632
  • solubility Miscible with acetone, benzene, carbon tetrachloride, and ether. Soluble in acetic acid, aniline, and carbon disulfide (Windholz et al., 1983).
  • pka16(at 25℃)
  • form Colorless liquid
  • Water Solubility 10.3 mM at 25 °C (shake flask-UV spectrophotometry, Streitwieser and Nebenzahl, 1976)
  • Henry's Law Constant5.1 at 25 °C (approximate - calculated from water solubility and vapor pressure)
  • Exposure limitsTLV-TWA 75 ppm (~202 mg/m3) (ACGIH, NIOSH, and OSHA); IDLH 2000 ppm (NIOSH).
  • Stability:Stable at room temperature. Incompatible with oxidizing agents, acids and a wide variety of other compounds. May form peroxides in storage. May undergo spontaneous polymerisation. Decomposes on heating. Highly flammable. Mixtures with air are explosive.
  • EPA Substance Registry SystemCyclopentadiene (542-92-7)
Safety Information
  • RIDADR 1993
  • HazardClass 3.2
  • PackingGroup III
  • ToxicityLD50 of dimer orally in rats: 0.82 g/kg (Smyth)
1,3-Cyclopentadiene Usage And Synthesis
  • Chemical Propertiescolourless liquid
  • Chemical PropertiesCyclopentadiene is a flammable, colorless liq- uid with a sweet odor, like turpentine.
  • Chemical Properties1,3-Cyclopentadiene is a colorless liquid that dimerizes easily in the presence of peroxides and trichloroacetic acid to a colorless solid.
  • Physical propertiesColorless liquid with a turpentine-like odor. Odor threshold concentration is 1.9 ppm (quoted, Amoore and Hautala, 1983).
  • UsesCyclopentadiene is used in the manufactureof resins, in the synthesis of sesquiterpenesand camphors, and as a ligand in the preparationof metal complexes.
  • Usesmanufacture of resins; in organic synthesis as the diene in the Diels-Alder reaction producing sesquiterpenes, synthetic alkaloids, camphors.
  • UsesIn manufacture of resins; in organic synthesis
  • DefinitionA cyclic hydrocarbon made by cracking petroleum. The molecules have a five-membered ring containing two carbon- carbon double bonds and one CH2 group. It forms the negative cyclopentadienyl ionC5H5-, present in sandwich compounds, such as ferrocene.
  • Definitioncyclopentadiene: A colourless liquidcyclic alkene,C5H6; r.d. 0.8021;m.p. –97.2°C; b.p. 40.0°C. It is preparedas a by-product during the fractionaldistillation of crude benzenefrom coal tar. It undergoes condensationreactions with ketones to givehighly coloured compounds (fulvenes)and readily undergoes polymerizationat room temperature togive the dimer, dicyclopentadiene.Cyclopentadiene itself is not an aromaticcompound because it does nothave the required number of pi electrons.However, removal of a hydrogenatom produces the stablecyclopentadienyl ion,C5H5-, whichdoes have aromatic properties. Inparticular, the ring can coordinate topositive ions in such compounds asferrocene.
  • Production MethodsThis compound occurs in the C6–C8 petroleum distillation fraction, and in coke oven light oil fractions. It is produced by dehydrogenation of cyclopentadiene or monomerization of its dimer.
  • General Description1,3-Cyclopentadiene is a colorless liquid with an irritating, terpene-like odor. Bp: 42.5°C; Flash point: 77°F. Density: 0.805 g cm-3.
  • Reactivity Profile1,3-Cyclopentadiene is incompatible with strong oxidizing agents. Ignites on contact with oxygen (O2) and ozone (O3). Explodes on contact with fuming nitric acid or a mixture of sulfuric acid and nitrogen tetroxide. Reacts vigorously on contact with potassium hydroxide and other strong bases. Mixtures with air are explosive. Presents a moderate explosion hazard when exposed to heat or flame. Decomposes violently at high temperature and pressure. May form explosive peroxides in storage. Undergoes a spontaneous dimerization at room temperature to give DI1,3-Cyclopentadiene (C10H12, CAS No: 77-73-6), which is a low-melting solid (melting point: 32.5°C). The reaction is strongly exothermic (Hazardous Chemicals Desk Reference, p. 360 (1987)), but occurs sufficiently slowly that 1,3-Cyclopentadiene can be said to be stable at room temperature. The dimerization accounts for the partial or complete solidification of liquid 1,3-Cyclopentadiene in storage. Polymerization occurs more rapidly and extensively at higher temperatures. When heated to 180-200°C, 1,3-Cyclopentadiene gives poly1,3-Cyclopentadiene, a white waxy solid. Stronger heating breaks down poly1,3-Cyclopentadiene and re-generates the monomeric 1,3-Cyclopentadiene as a vapor. The vapor decomposes violently at higher temperatures and pressures.
  • Health HazardCyclopentadiene exhibited low toxicity inanimals. Inhalation produced irritation of theeyes and nose. A 3-mL amount injected subcutaneouslyinto rabbits resulted in narcosis,convulsions, and death (von Oettingen 1940).A dose of≤ 1 mL was nontoxic. Repeatedexposure to 500 ppm caused liver and kidneyinjuries in rats; but longer repeated exposuresto 250 ppm produced no such effects in testanimals (ACGIH 1986). An oral LD50 valuein rats for the dimeric form has been recordedas 820 mg/kg (Smyth 1954).
  • Fire HazardFlammable liquid; flash point (open cup) 32°C (90°F); fire- extinguishing agent: dry chemical, foam, or CO2; a water spray may be used to cool the surroundings. Prolonged exposure to air may cause peroxide formation.
  • Safety ProfileLow toxicity by ingestion. A dangerous fire hazard when exposed to heat or flame; can react with oxidizing materials. Moderate explosion hazard in the form of gas when exposed to heat or by chemical reaction. It decomposes violently at hgh temperatures and pressures. dimerization is highly exothermic. Explosive reaction with fuming nitric acid,dinitrogen tetroxide, sulfuric acid. Reaction with nitrogen oxide + oxygen forms an explosive product. Reaction with oxygen forms a flame-sensitive explosive product. Ignites on contact with oxygen + ozone. Reacts vigorously on contact with potassium hydroxide. Incompatible with oxides of nitrogen, sulfuric acid. When heated to decomposition it emits acrid smoke and fumes.
  • Potential ExposureCyclopentadiene is used as an inter- mediate in the manufacture of resins, insecticides, fungi- cides, and other chemicals.
  • Environmental FateBiological. Cyclopentadiene may be oxidized by microbes to cyclopentanone (Dugan, 1972).
    Chemical/Physical. Dimerizes to dicyclopentadiene on standing (Windholz et al., 1983).
  • ShippingUN1993 Flammable liquids, n.o.s., Hazard Class: 3; Labels: 3-Flammable liquid, Technical Name Required.
  • Purification MethodsDry the diene with Mg(ClO4)2 and distil it rapidly as it dimerises readily at room temperature. It should be used immediately or stored in a Dry Ice or an ice-salt bath. HIGHLY FLAMMABLE. [Moffett Org Synth Coll Vol IV 238 1963.] Cyclopentadiene Dimer (4,7-methano-3a,4,7,7a-tetrahydroindene) has [77-73-6], M 132.3, m 33o, b 170o/atm, and d2 5 0.986; add ~0.05% of 2,6-di-tert-butyl-4-methylphenol as stabilizer. Cyclopentadiene is prepared when required by de-polymerising the technical grade dimer by heating it carefully under a fractionating column [Wilkinson Org Synth Coll Vol IV 467 1963], as described by Moffett (above reference), or by adding the dimer at a steady rate onto mineral oil heated at 240-270o (Korach et al. Org Synth 42 50 1962). [Beilstein 5 II 391.]
  • IncompatibilitiesVapors may form explosive mixture with air. Converted (dimerized) to higher-boiling dicyclopenta- diene upon standing in air and @ 32 F/0 C; this conversion may be violent and exothermic; this reaction is accelerated by peroxides or trichloroacetic acid. Reacts violently with potassium hydroxide. Violent reaction with strong oxidi- zers; strong acids; dinitrogen tetroxide; magnesium. Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoa- cids, epoxides, alkaline earth metals, nitrogen oxides. May accumulate static electrical charges, and may cause ignition of its vapors.
  • Waste DisposalDissolve or mix the material with a combustible solvent and burn in a chemical incinera- tor equipped with an afterburner and scrubber. All federal, state, and local environmental regulations must be observed.
1,3-Cyclopentadiene Preparation Products And Raw materials
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