Ethylene Oxide
A three-membered ring under so much strain it will open onto almost anything. That reactivity drives the glycol and surfactant chains, and it is also why ethylene oxide is one of the most hazardous products in routine bulk trade.
Molecular Structure
What is Ethylene Oxide?
Ethylene oxide is the simplest epoxide — two carbons and an oxygen closed into a three-membered ring. Forcing bond angles down to roughly 60°, when carbon and oxygen would prefer around 109°, stores something like 114 kJ/mol of ring strain in the molecule.
That strain is the product. Almost anything with an available lone pair — water, alcohols, amines, carboxylic acids — will attack a ring carbon and open it, releasing the strain and adding a two-carbon hydroxyethyl unit. Hydrolysis gives ethylene glycol, alcohols give the ethoxylate surfactants, ammonia gives the ethanolamines.
The same strain is why ethylene oxide is dangerous in a way that ordinary flammable gases are not. It polymerises exothermically if it meets an acid, a base, a metal oxide or simple rust, and its vapour can decompose explosively with no oxygen present at all — which is why its flammable range has no upper limit.
Chelora supplies ethylene oxide at ≥99.9 wt% under nitrogen pad, with acetaldehyde, water and acidity certified because each of them affects polymerisation stability. Supply is arranged only to facilities equipped and licensed for EO receipt and storage.
Quick Reference
Key Physical & Chemical Properties
Structure & Bonding
Three atoms in a closed ring, held at bond angles about 50° tighter than they want to be. Every important property of ethylene oxide — its reactivity, its polymerisation behaviour, its capacity for decomposition without air — comes from that strain looking for a way out.
Structure — strained three-membered oxirane ring
Structural Identity
- IUPAC NameOxirane
- Common namesEthylene oxide, EO, EtO
- Molecular FormulaC₂H₄O
- Molecular Weight44.05 g/mol
- RingThree-membered epoxide
- Bond lengths1.44 Å C–O; 1.47 Å C–C
- Ring bond angles≈ 60°, against ≈109° preferred
- Ring strain energy≈ 114 kJ/mol
- Key reactionNucleophilic ring opening
- CAS Number75-21-8
- InChI KeyIAYPIBMASNFSPL-UHFFFAOYSA-N
Product Specifications
Chelora supplies Ethylene Oxide in standard and custom grades. Contact us for specification sheets tailored to your process.
| Chemical name | Ethylene oxide |
|---|---|
| CAS Number | 75-21-8 |
| Molecular formula | C₂H₄O |
| Molecular weight | 44.05 g/mol |
| Purity (min) | ≥ 99.90 wt% |
| Water (max) | ≤ 100 ppm wt |
| Acetaldehyde (max) | ≤ 10 ppm wt |
| Acidity as acetic acid (max) | ≤ 10 ppm wt |
| Aldehydes total (max) | ≤ 20 ppm wt |
| Non-volatile residue (max) | ≤ 10 ppm wt |
| Iron (max) | ≤ 0.1 ppm wt |
| Chloride (max) | ≤ 0.5 ppm wt |
| Carbon dioxide (max) | ≤ 10 ppm wt |
| Appearance | Clear, colourless liquefied gas |
| Boiling point | 10.4 °C at 1 atm |
| Vapour pressure | ≈ 1.46 bar at 20 °C |
| Liquid density | 0.882 g/cm³ at 10 °C |
| Flash point | −20 °C (closed cup) |
| Autoignition temperature | 429 °C |
| Flammable limits | 2.6 – 100% v/v |
| Storage | Under nitrogen pad, refrigerated |
| UN Number | UN 1040 (Ethylene oxide with nitrogen) |
| IMDG / ADR Class | Class 2.3 (Toxic Gas), subsidiary risk 2.1 |
Downstream Applications & Derivatives
Key derivative chains and industrial uses of Ethylene Oxide.
Mono-, Di- & Triethylene Glycol
Hydrolysis gives MEG — by far the largest EO outlet — for polyester fibre and PET resin, with DEG and TEG as co-products for resins, humectants and gas dehydration.
Ethoxylates & Surfactants
Adding EO across fatty alcohols, alkylphenols and fatty acids gives the nonionic surfactant family behind detergents, emulsifiers, wetting agents and personal care formulations.
Ethanolamines
Reaction with ammonia gives mono-, di- and triethanolamine, used for acid gas scrubbing, detergents, cement grinding aids and herbicide salts.
Glycol Ethers & PEG
Reaction with alcohols gives glycol ethers for coatings and cleaners; controlled oligomerisation gives polyethylene glycols for pharmaceutical, cosmetic and industrial use.
Medical Device Sterilisation
Low-temperature gas sterilisation of heat-sensitive medical devices, where EO alkylates microbial DNA. Widely used because few alternatives handle complex or polymeric devices.
Choline Chloride & Specialities
Reaction with trimethylamine and HCl gives choline chloride for animal feed, alongside polyol initiators, corrosion inhibitors and specialty intermediates.
Why source Ethylene Oxide through Chelora Petrochem?
Verified Origin
Full origin certification and asset-backed supply chain documentation — no grey-market supply.
Grade Flexibility
High-purity grade supplied under nitrogen pad. Water, acidity, aldehyde and iron limits certified because each affects polymerisation stability in storage.
Full Documentation
CoA, SDS, UN transport docs, REACH compliance, and destination-market certificates with every shipment.
Logistics Support
Handled only into facilities equipped and licensed for ethylene oxide receipt — dedicated refrigerated pressure vessels, nitrogen padding, and full UN 1040 Class 2.3 documentation with pre-shipment facility verification.
Storage & Handling Guidelines
Always refer to the full SDS before handling. The following is a summary of key requirements.
- Supply and receipt only at facilities specifically designed, permitted and staffed for ethylene oxide — this is not a product that can be taken into general chemical storage.
- Keep the liquid under a nitrogen pad at all times and refrigerated below its 10.4 °C boiling point, with pressure and temperature alarmed and continuously monitored.
- Exclude every known polymerisation catalyst: acids, alkalis, amines, metal oxides, chlorides and rust. Vessels must be clean, dry and passivated before EO is admitted.
- Never let water into the system uncontrolled — hydrolysis is exothermic and the glycol formed can concentrate impurities that then catalyse polymerisation.
- Understand that EO vapour can decompose without any air present, so inerting alone does not remove the explosion hazard; deflagration protection and relief sizing must account for decomposition.
- Monitor tank temperature continuously; an unexplained temperature rise indicates polymerisation or decomposition has started and requires immediate emergency response.
- Run continuous fixed EO detection with alarms at ppm sensitivity, plus personal monitoring against the occupational exposure limit, which is at or below 1 ppm in most jurisdictions.
- Maintain a written EO-specific emergency plan covering leak response, cooling, evacuation distances and medical management, and exercise it.
Hazard Summary
Classification: Flam. Gas 1 (H220) · Press. Gas, liquefied (H280) · Carc. 1B (H350) · Muta. 1B (H340) · Repr. 1B (H360Fd) · Acute Tox. 3 inhalation (H331) · Skin Corr. 1 (H314) · Eye Dam. 1 (H318) · STOT SE 3 (H335).
Carcinogen, mutagen and reproductive toxicant: Ethylene oxide carries all three CMR classifications and is IARC Group 1, a known human carcinogen associated with lymphoid and breast cancer. In most jurisdictions this triggers specific regulatory duties — closed systems, exposure records, health surveillance and substitution assessment.
No upper flammable limit: The range runs from 2.6% all the way to 100%. Ethylene oxide vapour can decompose exothermically to carbon monoxide and methane with no oxygen present, propagating a deflagration through pure EO. Nitrogen inerting, which controls most flammable gases, does not eliminate this hazard.
Runaway polymerisation: Acids, bases, amines, metal oxides, chlorides and ordinary rust all catalyse violent exothermic polymerisation. Contamination of a storage vessel is a credible route to catastrophic failure, which is why vessel cleanliness and dedicated service are non-negotiable.
Exposure limits: The OSHA PEL is 1 ppm 8-hour TWA with a 5 ppm excursion limit and a 0.5 ppm action level; the ACGIH TLV is 1 ppm; the EU binding limit is 1.8 mg/m³ (about 1 ppm) with a skin notation. Detection systems must resolve well below these values.
Acute effects: Corrosive to skin and eyes, with delayed-onset blistering possible from liquid or high vapour contact. Inhalation causes respiratory irritation, nausea, headache and, at high concentration, pulmonary oedema and convulsions.
PPE minimum: Full-face supplied-air or SCBA respiratory protection for any potential exposure, butyl gloves and chemically resistant suit for transfer work, and eye protection at all times. Ordinary organic-vapour cartridges are not adequate for ethylene oxide.
Consult the full SDS for exposure limits, spill containment, emergency response, and disposal before any use.
Frequently Asked Questions
Technical and commercial questions about Ethylene Oxide sourcing and specifications.
What is ethylene oxide used for?
The great majority is hydrolysed to ethylene glycols — MEG for polyester fibre and PET resin above all, with DEG and TEG as co-products. The next largest outlets are ethoxylated nonionic surfactants for detergents and personal care, and the ethanolamines used in gas scrubbing and detergents. Glycol ethers, polyethylene glycols, choline chloride and low-temperature sterilisation of medical devices take the balance.
Why is ethylene oxide so reactive?
Ring strain. The three-membered ring forces bond angles to roughly 60° when carbon and oxygen would prefer around 109°, storing about 114 kJ/mol in the molecule. Any nucleophile that attacks a ring carbon opens the ring and releases that strain, which makes the reaction strongly favourable. It is exactly what makes EO such a useful building block, and exactly what makes it hazardous.
Why does ethylene oxide have no upper flammable limit?
Because it does not need oxygen to sustain a reaction. Most flammable gases stop burning once the mixture is too rich for the available oxygen. Ethylene oxide vapour can decompose exothermically on its own to carbon monoxide and methane, and that decomposition propagates as a deflagration through pure EO. The practical consequence is significant: nitrogen inerting, the standard control for flammable atmospheres, does not remove the explosion hazard, and relief and deflagration protection must be sized for decomposition.
What causes ethylene oxide to polymerise in storage?
Contamination. Acids, bases, amines, metal oxides, chlorides and ordinary rust all catalyse exothermic ring-opening polymerisation, and because the reaction generates heat it accelerates itself. This is why EO vessels must be clean, dry and passivated before filling, kept under nitrogen, kept cold, and dedicated to EO service rather than shared. An unexplained temperature rise in an EO tank is an emergency, not an anomaly to investigate later.
What are the health hazards of ethylene oxide?
It carries the full set of CMR classifications — Carc. 1B, Muta. 1B and Repr. 1B — and IARC classifies it as a Group 1 known human carcinogen, associated with lymphoid and breast cancers. It is also acutely toxic by inhalation and corrosive to skin and eyes. Occupational limits sit at or below 1 ppm, which means closed systems, continuous detection at ppm sensitivity, exposure records and health surveillance are regulatory requirements rather than best practice in most jurisdictions.
What does Chelora require before supplying ethylene oxide?
Confirmation that the receiving facility is designed, permitted and staffed for ethylene oxide — dedicated refrigerated pressure storage, nitrogen padding, EO-rated detection and relief systems, and trained personnel with an EO-specific emergency plan. Every shipment includes a Certificate of Analysis covering purity, water, acetaldehyde, acidity, aldehydes, non-volatile residue, iron, chloride and carbon dioxide; a Safety Data Sheet (GHS/REACH); UN 1040 Class 2.3 with subsidiary risk 2.1 documentation; and any destination-market licences required.
Request a quote or specification sheet
Talk to Chelora's sourcing team about Ethylene Oxide grade, volume, logistics, documentation, and lead times. We respond within one business day.
