Isoprene
Title: Isoprene
CAS Registry Number: 78-79-5
CAS Name: 2-Methyl-1,3-butadiene
Molecular Formula: C5H8
Molecular Weight: 68.12
Percent Composition: C 88.16%, H 11.84%
Literature References: Isoln from the products of the pyrolysis of natural rubber: Williams, Trans. R. Soc. London 150, 241 (1860); Boonstra, van Amerongen, Ind. Eng. Chem. 41, 161 (1949). Structure: Euler, Ber. 30, 1989 (1897). Prepn from turpentine: Tilden, J. Chem. Soc. 45, 410 (1884); Bibb, US 2386537 (1945 to Newport Ind.); from terpenes: Davis et al., Ind. Eng. Chem. 38, 53 (1946); Bourbon, US 2547684 (1951 to Manufacture de Caoutchouc Michelin); by condensation of isobutylene and formaldehyde in acetic acid: Blomquist, Verdol, J. Am. Chem. Soc. 77, 78 (1955); Chaffe et al., FR 1294716 (1962 to Inst. Francais du Petrole); by dehydrogenation of isoamylenes from cracked gasolines: GB 875346 (Apr. 21, 1960 to Shell Int. Res. Maatschappij); Voge et al., US 3110746 (1963 to Shell); by dimerization of propylene followed by pyrolysis of the resulting 2-methyl-2-pentene: Gorin, Oblad, US 2404056 (1946 to Socony-Vacuum Oil); GB 913852 (1962 to Goodyear); by dehydrogenation of isopentane: Dempsey, US 2914588 (1959 to Sun Oil); Owen, US 2982795 (1961 to Phillips Petroleum); Stevenson, US 3088986 (1963 to Air Products & Chem.); by reacting isoamylenes with methanol and pyrolizing and dehydrogenating the resulting tertiary ethers: Verdol, Walker, US 2972645 (1961 to Sinclair Refining). Toxicity: Gostinskii, C.A. 62, 15338a (1965). Reviews of isoprene and its polymers: Bean et al., "Isoprene Polymers" in Encyclopedia of Polymer Science and Technology vol. 7 (Interscience, New York, 1967) pp 782-855; Bailey, "Isoprene" in Vinyl and Diene Monomers (part 2), E. C. Leonard, Ed. (Wiley-Interscience, New York, 1971) pp 997-1148; W. M. Saltman in Kirk-Othmer Encyclopedia of Chemical Technology vol. 13 (Wiley-Interscience, New York, 3rd ed., 1981) pp 818-837; of carcinogenic risk: IARC Monographs 60, 215-232 (1994).
Properties: Colorless, volatile liquid. Unstable, oxidizable, flammable. bp760 34.067°. mp -145.95°. d420 0.681; d2020 0.6805. nD20 1.42160. Practically insol in water. Miscible with alcohol or ether. LD50 for mice: 144 mg isoprene vapors/l air (Gostinskii).
Melting point: mp -145.95°
Boiling point: bp760 34.067°
Index of refraction: nD20 1.42160
Density: d420 0.681; d2020 0.6805
Toxicity data: LD50 for mice: 144 mg isoprene vapors/l air (Gostinskii)
CAUTION: Respiratory irritation is a potential symptom of overexposure. May act as a CNS depressant and asphyxiant at high concns. See Patty's Industrial Hygiene and Toxicology vol. 2B, G. D. Clayton, F. E. Clayton, Eds. (John Wiley & Sons, New York, 4th ed., 1994) p 1252-1253. This substance is reasonably anticipated to be a human carcinogen: Report on Carcinogens, Eleventh Edition (PB2005-104914, 2004) p III-156.
Use: Manuf "synthetic" natural rubber, butyl rubber. Copolymer in the production of synthetic elastomers.

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