Isoprene
Nature's terpene building block, industrially supplied. A volatile, flammable liquid diene — feedstock for synthetic polyisoprene rubber, SIS block copolymers, and the terpene chemical family.
Molecular Structure
What is Isoprene?
Isoprene (2-methylbuta-1,3-diene) is a five-carbon conjugated diene — the structural repeat unit of natural rubber and terpene natural products. It is a volatile, colourless liquid at ambient conditions (bp 34 °C).
The 2-methyl group locks isoprene's two C=C bonds into a conjugated system with inherent s-cis accessibility, making it highly reactive in 1,4-polymerisation and Diels–Alder reactions. Ziegler–Natta or rare-earth (Nd) catalysis gives high-cis polyisoprene (IR) with properties closely matching natural rubber, while anionic polymerisation with lithium initiators gives SIS block copolymers.
Chelora sources isoprene from C₅ steam-cracker fractions, purified to ≥99.5% with TBC inhibitor and controlled cyclopentadiene and moisture levels. Supplied as stabilised liquid in tankers or drums.
Quick Reference
Key Physical & Chemical Properties
Structure & Bonding
Isoprene's reactivity is defined by its Conjugated diene with 2-methyl — the site of polymerisation and other industrially important reactions.
Lewis structure — sp² (C1–C4), sp³ (C5 methyl)
Structural Identity
- IUPAC Name2-Methylbuta-1,3-diene
- Molecular FormulaC₅H₈
- Molecular Weight68.12 g/mol
- Hybridisationsp² (C1–C4), sp³ (C5 methyl)
- Bond typeConjugated diene with 2-methyl
- C=C bond length1.34 Å (C=C)
- GeometryPlanar diene system; s-cis for Diels–Alder
- CAS Number78-79-5
- InChI KeyRRHGJUQNOFWUDK-UHFFFAOYSA-N
Product Specifications
Chelora supplies Isoprene in standard and custom grades. Contact us for specification sheets tailored to your process.
| Chemical name | Isoprene |
|---|---|
| CAS Number | 78-79-5 |
| Molecular formula | C₅H₈ |
| Molecular weight | 68.12 g/mol |
| Purity (standard grade) | ≥ 99.5 mol% |
| Purity (commercial grade) | ≥ 99.0 mol% |
| Physical state (ambient) | Volatile liquid (bp 34°C) |
| Boiling point | 34.1 °C at 1 atm |
| Melting point | −143.9 °C |
| Flammable limits | 1.5 – 8.9% v/v v/v in air |
| Cyclopentadiene (max) | ≤ 50 ppm wt |
| TBC inhibitor | 100–300 ppm wt |
| Carbonyl compounds (max) | ≤ 50 ppm wt |
| Moisture (max) | ≤ 50 ppm wt |
| Boiling point | 34.1 °C at 1 atm |
| Flash point | −54 °C (closed cup) |
| UN Number | UN 1218 |
| IMO / IMDG Class | Class 2.1 (Flammable Gas) |
Downstream Applications & Derivatives
Key derivative chains and industrial uses of Isoprene.
Polyisoprene Rubber (IR)
Ziegler–Natta or Nd-catalysed polymerisation gives synthetic polyisoprene (high-cis IR) — the synthetic equivalent of natural rubber, used in tyres, medical gloves, and pharmaceutical closures.
SIS Block Copolymers
Anionic sequential polymerisation gives styrene-isoprene-styrene (SIS) triblock copolymers — the basis of pressure-sensitive adhesives, hot-melt adhesives, and hygiene product elastic.
Butyl Rubber (IIR) Modifier
Copolymerisation of isoprene with isobutylene (typically 1–3 mol%) gives butyl rubber (IIR) — the isoprene provides the cure sites for vulcanisation in this otherwise saturated polymer.
Terpene & Terpenoid Chemistry
Isoprene is the C₅ building block of terpene natural products (the 'isoprene rule'). Used in synthesis of vitamins (E, K), fragrances, and pharmaceutical terpene intermediates.
Diels–Alder Syntheses
Isoprene is an excellent diene for Diels–Alder [4+2] cycloadditions with electron-poor dienophiles, used in fine chemical, pharmaceutical, and agrochemical intermediate synthesis.
Specialty Elastomers
Isoprene is used in specialty co-polymers and thermoplastic elastomers (SEPS, SEEPS), infrared-transparent optical films, and high-performance damping materials.
Why source Isoprene through Chelora Petrochem?
Verified Origin
Full origin certification and asset-backed supply chain documentation — no grey-market supply.
Grade Flexibility
Standard and custom grades available. Impurity specifications can be tailored to your process and catalyst system.
Full Documentation
CoA, SDS, UN transport docs, REACH compliance, and destination-market certificates with every shipment.
Logistics Support
Experienced in specialised chemical logistics for compressed gases and volatile liquids — Indian and international delivery.
Storage & Handling Guidelines
Always refer to the full SDS before handling. The following is a summary of key requirements.
- Store in a well-ventilated, dedicated area away from ignition sources, heat, and sunlight.
- All electrical equipment in storage and handling areas must be ATEX/IECEx rated for the applicable zone.
- Ensure full bonding and earthing of all transfer equipment during any transfer operation.
- Never store with strong oxidisers, halogens, or materials that generate static.
- Install continuous gas detection with audible and visual alarms set below the LEL.
- Use only approved pressure-rated piping, valves, and fittings with compatible materials.
- Conduct pre-use and post-use leak checks with suitable gas detection equipment.
- Maintain inhibitor levels where applicable; check on receipt and periodically during storage.
Hazard Summary
Classification: Flammable Gas/Liquid · Flammable limits 1.5 – 8.9% v/v v/v · UN 1218.
Flammability: Highly flammable — never rely on odour to detect leaks. Use continuous gas monitoring below LEL.
Health: Asphyxiant in enclosed spaces. Oxygen monitoring mandatory in confined areas. Follow occupational exposure limits (OELs) per SDS.
PPE minimum: Chemical goggles, appropriate gloves, flame-retardant clothing, and supplied-air respirator where oxygen deficiency is possible.
Consult the full SDS for exposure limits, spill containment, emergency response, and disposal before any use.
Frequently Asked Questions
Technical and commercial questions about Isoprene sourcing and specifications.
What is isoprene used for?
Isoprene is the feedstock for synthetic polyisoprene rubber (natural rubber equivalent), SIS thermoplastic elastomers and pressure-sensitive adhesives, butyl rubber cure sites, and terpene-based fine chemicals including vitamin E intermediates and fragrances.
Why does isoprene require an inhibitor?
Isoprene undergoes spontaneous free-radical dimerisation and polymerisation, especially in the presence of oxygen, heat, or light. TBC (tert-butylcatechol) inhibitor at 100–300 ppm is required to prevent runaway during storage. Cyclopentadiene — a reactive Diels–Alder impurity — must also be controlled below 50 ppm.
How is isoprene produced?
The main industrial route is extraction from the C₅ fraction of naphtha steam crackers using extractive distillation. Dehydrogenation of isopentane and isoamylenes is an alternative (Goodyear/BASF process). Fermentation-based bio-isoprene routes are in development but remain pre-commercial.
Is isoprene flammable and how must it be handled?
Yes — isoprene is a highly flammable liquid and vapour (flash point −54 °C, flammability range 1.5–8.9% v/v). It must be stored in sealed, inerted containers away from heat, ignition sources, and oxidising agents. TBC inhibitor must be maintained; oxygen-depleted headspace is recommended for bulk storage.
What is the CAS number and structure of isoprene?
Isoprene has CAS number 78-79-5, IUPAC name 2-methylbuta-1,3-diene, molecular formula C₅H₈, and molecular weight 68.12 g/mol. The structure has four sp²-hybridised carbons (conjugated diene) and a methyl group at C-2, which biases the s-cis conformation and modifies polymerisation microstructure.
What documentation does Chelora provide?
Every shipment includes a Certificate of Analysis covering purity, TBC level, cyclopentadiene, carbonyl compounds, and moisture; a Safety Data Sheet (GHS/REACH); UN 1218 Flammable Liquid Class 3 transport documentation; and any destination-market certificates.
Request a quote or specification sheet
Talk to Chelora's sourcing team about Isoprene grade, volume, logistics, documentation, and lead times. We respond within one business day.
