Isoprene is a colorless, flammable liquid with a pungent characteristic smell. It is readily soluble in diethyl ether, acetone, ethanol and other organic solvents; almost insoluble in water. It forms azeotropes with methanol, ethanol, acetone, isopentane. Isoprene exhibits most of the chemical properties of conjugated dienes. It is polymerizes readily to form dimers and high-molecular weight polymers, moreover, it is capable of polymerizing explosively when heated. To prevent spontaneous polymerization commercial isoprene is inhibited with 4-tert-butylcatechol of hydroquinone. Isoprene unit (-CH2-C(CH3)=CH-CH2) is abundant in nature. Natural rubber is a polymer of isoprene - most often cis-1,4-polyisoprene - with a molecular weight of 100,000 to 1,000,000. Some natural rubber sources called gutta percha are composed of trans-1,4-polyisoprene, a structural isomer which has similar, but not identical properties. The term terpene also refers to a class of naturally occurring compounds whose carbon skeletons are composed exclusively of isoprene units.
Most economically effective route for isoprene production is processing of C5 fraction which is a by-product of ethylene preparation by oil or naphtha thermal cracking. This fraction contains of 15-20% of isoprene, which is isolated by two-stage extractive rectification with acetonitrile or dimethylformamide (DMF). More than 70% of isoprene is manufactured by this method.
from isobutylene and formaldehyde:
for isoprene rubbers preparation (about 95% of isoprene production);
as a comonomer for production of butyl rubbers, isoprene-styrene thermoplastic elastomers, trans-polyisoprene;
as an intermediate in making of fragnances and pharmaceuticals;