Methyl Ethyl Ketone (MEK)
Acetone with one more carbon, which buys a slower evaporation rate and much better solvency for the resins that matter. It also makes n-hexane considerably more dangerous, which is worth knowing before the two share a workshop.
Molecular Structure
What is Methyl Ethyl Ketone (MEK)?
Methyl ethyl ketone is butan-2-one — a carbonyl with a methyl on one side and an ethyl on the other. That extra carbon over acetone raises the boiling point to 79.6 °C and slows evaporation to roughly two-thirds of acetone's rate, which is usually the reason it is chosen. It is also a markedly better solvent for nitrocellulose, vinyl and acrylic resins.
Unlike acetone, MEK is only partially miscible with water, dissolving to about 27% at ambient. It forms an azeotrope with water that boils at 73.5 °C, which is what makes recovery by distillation a specific piece of process design rather than a straightforward separation.
Most production is by dehydrogenation of secondary butanol, itself made by hydrating n-butene from a C4 stream. That places MEK downstream of the same refinery and cracker C4 cut that supplies butadiene, so its availability tracks C4 economics rather than the coatings market it serves.
MEK substantially increases the neurotoxicity of n-hexane. It induces the enzyme that converts hexane into the metabolite responsible for peripheral nerve damage, so workers exposed to both together are at far greater risk than exposure to either alone would suggest. Any shop running both solvents should be assessed on that basis.
Quick Reference
Key Physical & Chemical Properties
Structure & Bonding
A carbonyl carbon carrying a methyl on one side and an ethyl on the other. The asymmetry is what separates MEK from acetone — one extra carbon slows evaporation, raises the boiling point and broadens solvency for the resins used in coatings and adhesives.
Skeletal structure — carbonyl with methyl and ethyl substituents
Structural Identity
- IUPAC NameButan-2-one
- Common namesMEK, methyl ethyl ketone, 2-butanone
- Molecular FormulaC₄H₈O
- Molecular Weight72.11 g/mol
- Functional groupKetone carbonyl
- Water azeotrope≈ 11% water, boils 73.5 °C
- EvaporationSlower than acetone, faster than toluene
- Made fromsec-Butanol dehydrogenation
- Peroxide riskForms peroxides on prolonged air exposure
- CAS Number78-93-3
- InChI KeyZWEHNKRNPOVVGH-UHFFFAOYSA-N
Product Specifications
Chelora supplies Methyl Ethyl Ketone (MEK) in standard and custom grades. Contact us for specification sheets tailored to your process.
| Chemical name | Methyl ethyl ketone |
|---|---|
| CAS Number | 78-93-3 |
| Molecular formula | C₄H₈O |
| Molecular weight | 72.11 g/mol |
| Purity (min) | ≥ 99.50 wt% |
| Water (max) | ≤ 0.10 wt% (Karl Fischer) |
| Acidity as acetic acid (max) | ≤ 0.005 wt% |
| Colour (max) | ≤ 10 Pt-Co (Hazen) |
| Specific gravity | 0.8045 – 0.8065 at 20/20 °C |
| Distillation range | 78.5 – 80.5 °C |
| Non-volatile residue (max) | ≤ 5 ppm wt |
| Peroxides as H₂O₂ (max) | ≤ 5 ppm wt |
| Methanol (max) | ≤ 0.05 wt% |
| sec-Butanol (max) | ≤ 0.10 wt% |
| Odour | Characteristic, non-residual |
| Flash point | −9 °C (closed cup) |
| Autoignition temperature | 505 °C |
| Flammable limits | 1.8 – 11.5% v/v in air |
| Transport classification | UN 1193, Class 3, PG II |
Downstream Applications & Derivatives
Key derivative chains and industrial uses of Methyl Ethyl Ketone (MEK).
Coatings & Thinners
A primary solvent for nitrocellulose, vinyl, acrylic and epoxy systems, and a standard component in lacquer thinners where a mid-evaporation ketone is needed.
Printing Inks
Flexographic and gravure ink solvent, particularly for vinyl and polyamide resin systems, where release from the printed film matters as much as dissolution.
Adhesives & PVC Cement
Contact adhesives, and the solvent-weld cement used to join PVC and ABS pipe, where MEK softens the surface enough for the joint to fuse.
Lube Oil Dewaxing
The MEK-toluene solvent dewaxing process removes wax from lubricating base oils at refinery scale — one of the largest single uses of the solvent.
MEK Peroxide
Converted to MEKP, the standard room-temperature initiator for curing unsaturated polyester resin in FRP laminating and casting.
Cleaning & Degreasing
Surface preparation, tool and equipment cleaning, and synthetic leather and magnetic media manufacture, where fast clean evaporation is required.
Why source Methyl Ethyl Ketone (MEK) through Chelora Petrochem?
Verified Origin
Full origin certification and asset-backed supply chain documentation — no grey-market supply.
Grade Flexibility
Technical and low-water grades supplied. We certify peroxide content as well as the standard assay, because peroxide level is what governs safe storage life rather than purity.
Full Documentation
CoA, SDS, UN 1193 transport documents, REACH compliance, and destination-market certificates with every shipment.
Logistics Support
Experienced in flammable solvent logistics — dedicated road tankers and ISO tanks with bonding, earthing and vapour-return provision, plus drums and IBCs, for 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 earthed and bonded tanks with pressure/vacuum relief and flame arrestors, under a nitrogen blanket where practical — nitrogen also suppresses peroxide formation.
- Test for peroxides before distilling, evaporating or drawing down a drum that has been open or stored long. MEK forms peroxides on prolonged contact with air, and concentrating them by distillation is the scenario that causes incidents.
- Date every container on opening and observe a defined maximum storage period. Peroxide risk is a function of time and air exposure, not of purity on arrival.
- Treat all transfers as a static ignition hazard. Flash point is −9 °C, so ignitable vapour is present at every ambient temperature — bond and earth all connections and avoid splash filling.
- Assess co-exposure with n-hexane specifically. MEK induces the metabolic pathway that makes hexane neurotoxic, so a workshop using both needs its exposure assessment done on the combination rather than on each solvent separately.
- Ventilate to keep vapour below the lower flammable limit of 1.8%, and classify the area for electrical equipment. Vapour is heavier than air and collects at low level.
- Exclude strong oxidisers, nitric acid, peroxides and strong bases. Reaction with oxidisers is vigorous.
- Check compatibility before selecting hoses, gaskets and liners. MEK attacks many plastics and elastomers, and it dissolves the resins it is chosen for — including some tank linings.
- Provide eyewash and safety showers, use non-sparking tools, and keep containers closed when not in active use.
Hazard Summary
Classification: Flam. Liq. 2 (H225), Eye Irrit. 2 (H319), STOT SE 3 (H336, may cause drowsiness or dizziness). MEK is not classified as a carcinogen, mutagen or reproductive toxicant, and it was removed from the US EPA hazardous air pollutant list in 2005.
Potentiation of n-hexane neurotoxicity: this is the least obvious and most important hazard associated with MEK. MEK induces cytochrome P450 2E1, the enzyme that converts n-hexane into 2,5-hexanedione, the metabolite that damages peripheral nerves. Workers exposed to both solvents together develop neuropathy at hexane concentrations that would otherwise be tolerated. Adhesive, footwear and electronics operations frequently use both, and the combined risk is routinely missed in assessments that consider each substance individually.
Peroxide formation: like other ketones and ethers, MEK forms peroxides on prolonged exposure to air. The peroxides are non-volatile, so they concentrate in the residue if the solvent is distilled or evaporated to dryness, and can then detonate. Test before distillation and observe container-open dating.
Flammability: a flash point of −9 °C means ignitable vapour at all normal ambient temperatures, with a flammable range from 1.8% to 11.5%. Vapour is heavier than air and travels along the ground to remote ignition sources.
Health: irritating to the eyes and respiratory tract, and high vapour concentrations cause drowsiness and dizziness. Repeated skin contact defats the skin and causes dermatitis.
Materials compatibility: MEK attacks a wide range of plastics, elastomers and coatings, including several used in hoses and tank linings. Confirm compatibility for every wetted component rather than assuming solvent-service parts are adequate.
PPE minimum: chemical goggles, gloves selected for ketone service, antistatic clothing and footwear at transfer points, with respiratory protection where ventilation cannot control vapour.
Consult the full SDS for exposure limits, spill containment, emergency response and disposal before any use.
Frequently Asked Questions
Technical and commercial questions about Methyl Ethyl Ketone (MEK) sourcing and specifications.
What is MEK used for?
Coatings and thinners take a large share — it is a primary solvent for nitrocellulose, vinyl and acrylic resin systems. Printing inks for flexographic and gravure work are another major outlet, as are contact adhesives and the solvent cement used to weld PVC and ABS pipe. At refinery scale, MEK-toluene solvent dewaxing removes wax from lubricating base oils. Smaller volumes go into MEK peroxide for curing polyester resins, and into cleaning and surface preparation.
How does MEK compare with acetone?
MEK is the same chemistry with one more carbon, and the differences follow from that. It boils at 79.6 °C against acetone's 56 °C, evaporates at roughly two-thirds the rate, and is a stronger solvent for the higher molecular weight resins used in coatings and adhesives. Acetone is fully miscible with water; MEK dissolves only to about 27%, which matters for both formulation and recovery. On the other side, MEK's flash point is higher at −9 °C against −20 °C, but both are ignitable at any ambient temperature. In practice acetone is chosen when the fastest possible flash-off is wanted, MEK when the film needs a little longer to level.
Why does MEK need testing for peroxides?
Because it forms them slowly on contact with air, and the consequences show up later. The peroxides are much less volatile than the solvent, so if MEK is distilled or a container is evaporated down, the peroxides concentrate in the residue where they can become shock or heat sensitive. The practical controls are to date containers when they are opened, keep a maximum storage period, blanket bulk storage with nitrogen, and test for peroxides before any distillation or evaporation step. This is routine practice with ethers and is equally applicable here, though less consistently observed.
Why does MEK matter for n-hexane exposure?
Because it changes how the body handles hexane. n-Hexane itself is not the neurotoxin — the damage is done by 2,5-hexanedione, a metabolite produced by cytochrome P450 2E1. MEK induces that enzyme, so a worker exposed to both converts more of the absorbed hexane into the harmful metabolite. Peripheral neuropathy has been documented in workers exposed to hexane-MEK mixtures at hexane concentrations that would not have been expected to cause it. Adhesive formulation, footwear manufacture and electronics cleaning commonly involve both, so any exposure assessment covering these operations needs to treat the combination rather than each substance separately.
What is MEK dewaxing?
It is the standard refinery process for removing wax from lubricating base oil. Waxy oil is diluted with a mixture of MEK and toluene and chilled, and the wax crystallises out and is filtered off. The two solvents do different jobs: toluene keeps the oil in solution at low temperature, while MEK selectively rejects the wax so it crystallises cleanly and filters well. The proportions are adjusted to hit the target pour point. It is one of the largest single uses of MEK by volume and is quite separate from the coatings and adhesives market that most MEK buyers operate in.
What documentation does Chelora provide?
Every shipment includes a Certificate of Analysis covering purity, water, acidity, colour, specific gravity, distillation range, non-volatile residue, peroxide content and residual sec-butanol and methanol; a Safety Data Sheet to GHS and REACH format; UN 1193 Class 3 dangerous goods documentation; an origin certificate; and destination-market certificates where required.
Request a quote or specification sheet
Talk to Chelora's sourcing team about Methyl Ethyl Ketone (MEK) grade, volume, logistics, documentation, and lead times. We respond within one business day.
