ISOPRENE - (78-79-5)

Introduction

Name: isoprene; isopentadiene; 2-methyl-1,3-butadiene
* IUPAC
CAS Number: 78-79-5
Chemical Formula: C5H8 or CH2C(CH3)CHCH2
Molar Mass: 68.11702 g
Mass Percent: C 88.162 %; H 11.837 % 
Isomers:  cyclopentene  •  cis-piperylene  •  piperylene  •  1,4-pentadiene  •  2-pentyne

Classification

• organic • diene

Uses/Function

• "Natural rubber has been known to humans for hundreds of years. Archaeologists have found that the Indians of South and Central America were making rubber products as early as the eleventh century. Until the end of the nineteenth century, natural supplies of rubber obtained from the rubber tree, Hevea brasiliensis, were sufficient to meet consumer demand for the product. However, with the development of modern technology - especially the invention of the automobile - natural suppies of the product proved to be insufficient to meet growing demand. Chemical researchers began to look for ways of producing synthetic forms of rubber.

One approach was to attempt making synthetic rubber with exactly the same chemical composition as that of natural rubber, that is, a polymer of trans-polyisoprene. As early as the 1880s, British chemist Sir William Augustus Tilden (1842-1926) was successful in achieving this objective. Tilden found that he could make isoprene by heating turpentine (C10H16). The isoprene then polymerized easily when exposed to light. After more than twenty years of research, however, Tilden decided that synthetic trans-polyisoprene could never be made economically, and he encouraged his friends to forget about the process.

Over the years, chemists did find ways of making other types of synthetic rubber, and some never abandoned the effort to make synthetic trans-polyisoprene. The critical breakthrough needed in this research occurred in about 1953 when Swiss chemist Karl Ziegler (1898-1973) and Italian chemist Giulio Natta (1903 -1979) each found a way of polymerizing isoprene in such a way that its geometric structure matched that of natural rubber exactly. A year later, chemists at two of the largest rubber companies in the world, B. F. Goodrich and Firestone, announced that they had developed methods for making synthetic trans-polyisoprene using essentially the methods developed earlier by Ziegler and Natta.

In the early twenty-first century, more than 95 percent of the isoprene produced is used to make trans-polyisoprene synthetic rubber. The remaining 5 percent is used to make other types of synthetic rubber and other kinds of polymers. A small amount of the compound is used as a chemical intermediary, a substance from which other organic chemicals is made.

Isoprene is a dangerous fire hazard. It also poses a risk to human health and that of other animals. It is an irritant to skin, eyes, and the respiratory system. Upon exposure, it produces symptoms such as redness, watering, and itching of the eyes and itching, reddening, and blistenng of the skin. If inhaled, it can irritate the lungs and respiratory system. Isoprene is a known carcinogen.

1

• "Manuf[acture] "synthetic" natural rubber, butyl rubber. Copolymer in the production of synthetic elastomers." 2

Bonding

Bonding: polar covalent
Ionic Character: 10.61 %

For More Information

Wikipedia
Magazines:
Perkins, Sid. Team Identifies New Path to Haze. Science News, August 29, 2009, p 15.

Sources

(1) - Schlager, Neil, Weisblatt, Jayne, Newton, David E., and Montney, Charles B. Chemical Compounds Vol. 2; Thomson-Gale: Detroit, MI, 2006; pp 383-4.
(2) - The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 13th ed.; Budavari, S.; O'Neil, M.J.; Smith, A.; Heckelman, P. E.; Kinneary, J. F., Eds.; Merck & Co.: Whitehouse Station, NJ, 2001; entry 5220.