Isoprenyl

Isoprene

Names
Preferred IUPAC name 2-Methylbuta-1,3-diene
Other names 2-Methyl-1,3-butadiene Isoprene
Identifiers
CAS Number	78-79-5 Yd
3D model (Jmol)	Interactive image
ChEBI	CHEBI:35194 Y
ChemSpider	6309 Y
ECHA InfoCard	100.001.040
KEGG	C16521 Y
PubChem CID	6557
UNII	0A62964IBU Y
InChI InChI=1S/C5H8/c1-4-5(2)3/h4H,1-2H2,3H3 Y Key: RRHGJUQNOFWUDK-UHFFFAOYSA-N Y InChI=1/C5H8/c1-4-5(2)3/h4H,1-2H2,3H3 Key: RRHGJUQNOFWUDK-UHFFFAOYAS
SMILES CC(=C)C=C
Properties
Chemical formula	C5H8
Molar mass	68.12 g/mol
Density	0.681 g/cm3
Melting point	−143.95 °C (−227.11 °F; 129.20 K)
Boiling point	34.067 °C (93.321 °F; 307.217 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Isoprene, or 2-methyl-1,3-butadiene, is a common organic compound with the formula CH₂=C(CH₃)−CH=CH₂. In its pure form it is a colorless volatile liquid. Isoprene is produced by many plants, and its polymers are the main component of natural rubber. C. G. Williams named the compound in 1860 after obtaining it from thermal decomposition (pyrolysis) of natural rubber; he correctly deduced the empirical formula C₅H₈.

Isoprene is produced and emitted by many species of trees (major producers are oaks, poplars, eucalyptus, and some legumes). Yearly production of isoprene emissions by vegetation is around 600 million metric tons, half from tropical broadleaf trees and the remainder primarily from shrubs. This is about equivalent to methane emissions and accounts for ~1/3 of all hydrocarbons released into the atmosphere.

Isoprene is made through the methyl-erythritol 4-phosphate pathway (MEP pathway, also called the non-mevalonate pathway) in the chloroplasts of plants. One of the two end products of MEP pathway, dimethylallyl pyrophosphate (DMAPP), is catalyzed by the enzyme isoprene synthase to form isoprene. Therefore, inhibitors that block the MEP pathway, such as fosmidomycin, also block isoprene formation. Isoprene emission increases dramatically with temperature and maximizes at around 40 °C. This has led to the hypothesis that isoprene may protect plants against heat stress (thermotolerance hypothesis, see below). Emission of isoprene is also observed in some bacteria and this is thought to come from non-enzymatic degradations from DMAPP.

Isoprene emission in plants is controlled both by the availability of substrate (DMAPP) and by enzyme (isoprene synthase) activity. In particular, light, CO₂ and O₂ dependencies of isoprene emission are controlled by substrate availability, whereas temperature dependency of isoprene emission is regulated both by substrate level and enzyme activity.