isoprene


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Related to isoprene: isoprene rule

isoprene

or

2-methyl-1,3-butadiene

(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.)

Isoprene

 

(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.

isoprene

[′ī·sə‚prēn]
(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 ?
Styrene, butadiene, and isoprene used in this study were polymerization grade and provided by the Sinopec Shanghai Petrochemical Company Limited.
On hot, windless days in the Blue Ridge Mountains stretching from Georgia to Pennsylvania, a bluish haze of isoprene gas often settles over the forest canopy.
Jason Surratt, assistant professor of environmental sciences and engineering, reveals one mechanism by which isoprene contributes to the production of these tiny, potentially health-damaging particles.
A fermentation process for isoprene has been developed by Danisco in partnership with Goodyear as well as by Amyris in partnership with Michelin and others, predominantly for tire applications.
Genetic engineering might be used to reduce isoprene emissions, it said.
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.
RS Butyl rubber is essentially poly(isobutene) with two mol per cent of isoprene in the polymer chain.
The acquisition enables TSRC to raise annual production capacities by 30,000 tons of SIS (styrene isoprene styrene) and 32,000 tons of SBS (styrene butadiene styrene) in the second quarter of this year, as well as become an integrated supplier of SBS and to become a top-five producer globally of SBC (styrenic block copolymer).
These include the biosynthesis and emission of isoprene, methylbutanol, and other volatile plant isoprenoids; analyzing the plant volatile fraction; plant volatile signaling; pheromones in chemical communication; using volatiles in pest control; challenges in synthesizing natural and non-natural volatiles; the biosynthesis of volatile sulfur flavor compounds; the thermal generation of aroma-active volatiles in food; human olfactory perception; perfumery; micro-encapsulation techniques for food flavor; pro-fragrances and pro-perfumes; and reactions of biogenic volatile organic compounds in the atmosphere.
The natural pollutant in question here is called isoprene (which is formed naturally in plants and animals and is a precursor of ozone).
Melnick's research has advanced the understanding of the toxicity of widely used industrial chemicals such as butadiene, isoprene and glycol esters as well as drinking water disinfection by-products such as chloroform.
A line of standard and custom flat drive belts made of neoprene or isoprene for vacuum cleaners and sweepers, conveyors and various industrial and commercial products is available from Flexaust.