Nomenclature
CAS number: 542-92-7
1,3-Cyclopentadiene.
C
5H
6; mol wt 66.10.
C 90.85%, H 9.15%.
Description and references
Obtained from the distillates produced in carbonization
of coal, esp from the foreruns of coke-oven light oil: Ward, US 2211038 (1940); process involving the liquefaction
of coke-oven gas: Horclois, Chim. Ind. (Paris), special issue April 1934, pp 357-363. Also obtained during the
cracking of petr hydrocarbons: Tropsch et al., Ind. Eng. Chem. 30, 169 (1938); cf. Dedussenko, J. Gen. Chem. USSR 7, 1467 (1937); Chem. Zentralbl. 109, I, 793 (1938). Synthesis by passing vaporized cyclopentane
over activated alumina and oxides of molybdenum, chromium, or vanadium:
Grosse et al., Ind. Eng. Chem. 32, 309 (1940); US 2157202; US 2157203; US 2157939. Lab prepn by depolymerization of dicyclopentadiene: Moffett, Org. Synth. coll. vol. IV, 238 (1963). Toxicity study: Smyth et al., Arch. Ind. Hyg. Occup. Med. 10, 61 (1954). Review and discussion of structure:
Wilson, Wells, Chem. Rev. 34, 1 (1944). Review: M. Fefer, A. B. Small in Kirk-Othmer Encyclopedia of Chemical Technology vol. 7 (Wiley-Interscience, New York, 3rd ed., 1979)
pp 417-429.
Properties
Liquid. d40 0.8235; d410 0.8131; d420 0.8021; d425 0.7966; d430 0.7914. mp -85°. bp760 41.5-42.0°. nD16 1.44632. Absorption spectum: Pickett et al., J. Am. Chem. Soc. 63, 1073 (1941). Insol in water. Miscible with alc,
ether, benzene, carbon tetrachloride. Sol in carbon disulfide, aniline,
acetic acid, liquid petrolatum. Cyclopentadiene polymerizes to dicyclopentadiene
on standing. Polymerization is accelerated by the presence of peroxides
or trichloroacetic acid. The dimer is cryst, mp 32.5°, with a camphor-like odor, having the
structure of a partially hydrogenated indene contg a bridged methylene
group. It is a more convenient form in which to handle cyclopentadiene,
and is easily depolymerized by distilling at atmospheric pressure.
LD50 of dimer orally in rats: 0.82 g/kg (Smyth).Caution
Potential symptoms of overexposure
are irritation of eyes and nose. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140,
1997) p 86.Use
Manuf resins; in organic synthesis as the diene
in the Diels-Alder reaction producing sesquiterpenes, synthetic alkaloids,
camphors.