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(ī`səprēn, byo͞o'tədī`ēn), colorless liquid organic compound. It is a hydrocarbon, and is insoluble in water but soluble in many organic solvents; it boils at 34°C;. The isoprene molecule contains two double bonds. It is readily polymerized by the use of special catalysts; large numbers of isoprene molecules join together to form a single large, threadlike polyisoprene molecule. Isoprene polymers also occur naturally. The natural rubber caoutchouc is cis-1,4-polyisoprene, and trans-1,4-polyisoprene is present in the natural rubbers balata and gutta-percha. (The cis and trans polyisoprenes are structural isomers.)



(2-methyl-l, 3-butadiene), an unsaturated aliphatic hydrocarbon, CH2=C(CH3)—CH=CH2. It is a colorless, mobile, highly volatile inflammable liquid with a characteristic odor. Its melting point is — 145.95°C; boiling point, 34.067°C; flash point, -48°C; density, 0.681 g/cm3 (20°C); refractive index nD20, 1.42194; and heat of polymerization, —74.9 kJ/mole (—17.9 kcal/mole). Mixtures of isoprene and air are explosive at volume concentrations of 1.66–11.5 percent. Isoprene is insoluble in water but readily soluble in most hydrocarbon solvents. It forms binary azeotropes with such compounds as methanol, ethanol, acetone, diethyl ether, and carbon disulfide, as well as ternary azeotropes, for example, with acetone and water. Addition occurs readily between isoprene and hydrogen, halogens, hydrogen halides, and primary and secondary amines across the double bonds. An important property of isoprene is the capacity to easily polymerize and copolymerize, for example, with butadiene, styrene, acrylonitrile, and propylene.

The basic industrial methods of preparing isoprene are (1) the reaction of isobutylene with formaldehyde to give 4, 4-dimethyl-1, 3-dioxane, followed by catalytic decomposition of the latter to isoprene and formaldehyde (the so-called dioxane method); (2) the catalytic dehydrogenation of isopentane and isoamylenes; and (3) dimerization of propylene to 2-methyl-l-pentene, followed by isomerization to 2-methyl-2-pentene, followed by pyrolysis (650°-800°C) to isoprene. In addition, isoprene can be separated from the gases resulting during the thermal decomposition of petroleum products (from a C5 fraction of the byproducts of ethylene production).

Isoprene is stored in the presence of inhibitors, such as hydroquinone, to prevent spontaneous polymerization. In high concentrations isoprene acts as a narcotic; in low concentrations it stimulates the mucous membrane. The maximum permissible concentration of isoprene in air is 40 mg/m3. Isoprene is used to make isoprene rubbers and butyl rubber.


(organic chemistry)
C5H8 A conjugated diolefin; a mobile, colorless liquid having a boiling point of 34.1°C; insoluble in water, soluble in alcohol and ether; polymerizes readily to form dimers and high-molecular-weight elastomer resins.
References in periodicals archive ?
Polymer grade isoprene is likely to witness significant revenue rise at a CAGR of 7.
Some of Berlin's oldest and most impressive trees are plane trees -- which release a lot of isoprene -- as do poplars.
On sunny days 42% of the isoprene emission comes from top of the canopy and only 2% from bottom of the canopy.
Styrene, butadiene, and isoprene used in this study were polymerization grade and provided by the Sinopec Shanghai Petrochemical Company Limited.
CB & I have been chosen as the licensor of the MTBE producing unit which is designed to produce a number of high-value components, such as isoprene, benzene, toluene and xylenes.
The research by scientists at the Maxine Dunitz Neurosurgical Institute and Department of Neurosurgery at Cedars-Sinai will be done in laboratory mice and will focus on three - naphthalene, butadiene and isoprene - that often are associated with polluted air.
However, in 2004, researchers, contrary to popular assumptions, revealed that isoprene likely was involved in the production of particulate matter, tiny particles that can get lodged in lungs, lead to lung cancer and asthma, and damage other tissues as well as the environment--but exactly how was anybody's guess.
These include ethanol, n- and iso-butanol, poly(hydroxyalkanoates), lactic acid, 3-hydroxypropionic acid, diacids (such as succinic, fumaric, and adipic), diols (such as 1,4-butanediol and 1,3-propanediol), isoprene, farnesene, and other olefins from alcohol dehydration: ethylene, propylene, and butadiene.
Poplar, willow or eucalyptus trees, all used as fast-growing sources of renewable wood fuel, emit high levels of the chemical isoprene as they grow, the study said.
It is working with DuPont Industrial Biosciences to develop a bio-based alternative to isoprene, an oil derivative used to produce synthetic rubber.
Tokyo, June 1, 2012 - (JCN) - Bridgestone has successfully polymerized high-cis polyisoprene (IR) synthetic rubber from isoprene provided by Ajinomoto, a partner in synthetic rubber development for tires.