What Is Isoprene?
Isoprene is a hydrocarbon with two double bonds.
In nature, it is formed from mevalonic acid, an intermediate substance formed from sugar. Polyisoprene, a polymer of isoprene, is naturally obtained from the sap of the rubber tree in the tropics and is also called natural rubber.
Industrially, isoprene is produced as a byproduct of the thermal cracking of petroleum-derived naphtha and can be used as a raw material for polyisoprene rubber, a type of synthetic rubber used in automobile tires.
| Chemical Formula | C5H8 |
| English Name | Isoprene |
| Molecular Weight | 68.12 |
| Melting Point | -145.9 °C |
Uses of Isoprene
Isoprene is mainly used as a raw material for polyisoprene rubber and butyl rubber, which are synthetic rubbers. Approximately 70% of polyisoprene rubber is used in automobile and aircraft tires.
In addition, its high biocompatibility allows it to be used in the medical field. Specifically, it is used in rubber bags for ultrasound machines and components for blood circuits.
In addition to synthetic rubber, isoprene is used as a raw material for geraniol and linalool, as a raw material for fragrances, and as a raw material for agrochemical intermediates such as chrysanthemum acid.
Properties of Isoprene
Isoprene has a melting point of -145.95°C and a boiling point of 34.067°C. It is a colorless liquid that is highly volatile at room temperature. It has an odor similar to that of rubber or city gas. It is highly flammable and combustible, and there is a risk of explosion when present in atomized form in the atmosphere.
Structure of Isoprene
Isoprene is a type of diene with two double bonds. Its chemical formula is C5H8 and its molecular weight is 68.12. It is also called 2-methyl-1,3-butadiene.
Other Information on Isoprene
1. Polyisoprene Synthesis
Isoprene was first isolated by pyrolysis of natural rubber. Industrially, about 800,000 tons of isoprene are produced each year. Ninety-five percent of the isoprene produced is used as a monomer for the synthesis of cis-1,4-polyisoprene, an artificial natural rubber.
Natural rubber is an addition polymer composed of 100,000 to 1,000,000 isoprene molecules. The basic structure is almost exclusively cis-1,4-polyisoprene. However, natural rubber may contain a small amount of trans-1,4-polyisoprene, a stereoisomer of cis-1,4-polyisoprene. In addition, natural rubber contains trace amounts of fatty acids, proteins, and inorganic substances.
2. Natural Compounds With Isoprene as the Structural Unit
Natural organic compounds called isoprenoids and terpenoids have isoprene as their structural unit. As living substances, they are made by insects, plants, bacteria, and fungi, and are the names given to compounds with 10 carbons found in essential oils. The molecular formula of these hydrocarbons is (C5H8)n, expressed as a multiple of isoprene.
Examples of isoprenoids and terpenoids include limonene, which has two isoprene units, and farnesol, which has three isoprene units. Limonene and farnesol can be used as flavoring agents; vitamin A, which is composed of four isoprene units, is also a terpenoid.
3. Functional Isoprene Units in Natural Compounds
The precursors required for the biosynthesis of terpenes and terpenoids also contain isoprene units. In biological systems, the functional isoprene units are dimethylallyl pyrophosphate and isopentenyl diphosphate. Isopentenyl diphosphate is an isomer of dimethylallyl diphosphate.