1,2-Epoxydodecane at a Glance
1,2-Epoxydodecane (CAS 2855-19-8) is a straight-chain terminal epoxide: an oxirane ring at the end of a twelve-carbon chain. Formula C12H24O, molecular weight 184.32, one epoxide group per molecule. It belongs to the alpha-olefin oxide family – the C6 to C14 homologues made by epoxidising the corresponding 1-alkene – and it is the middle of that series: volatile enough to handle at room temperature, hydrophobic enough to plasticise and to keep water out, and with an epoxide equivalent weight (184.3 g/eq) that sits almost exactly on top of a standard liquid DGEBA resin.
That last coincidence is why the C12 grade is interesting commercially. A reactive diluent is normally chosen for viscosity, and then the formulator discovers that it has moved the stoichiometry and the glass transition temperature. With an EEW within one gram of the base resin, C12 barely moves the cure ratio at all while still cutting viscosity – a different trade-off from the short-chain grades, which dilute harder but demand more hardener and terminate more chains. PolyBlueChem supplies it at 96.0% min as a colourless liquid; this article covers the chemistry, the manufacture, the specification that matters and the arithmetic of using it.
Chemical and Physical Profile
| Property | Value | Note |
|---|---|---|
| CAS number | 2855-19-8 | Also called 1,2-epoxydodecane, dodecene oxide, dodecylene oxide |
| Formula / MW | C12H24O / 184.32 g/mol | PubChem record for this CAS |
| Structure | Terminal oxirane, C10 alkyl tail | CH3(CH2)9-CH-CH2O (ring) |
| Functionality | 1 epoxide group | Monoepoxide – a chain terminator, not a crosslinker |
| Epoxy equivalent weight (calculated) | 184.3 g/eq | 184.32 / 1 |
| Epoxy value (calculated) | 0.54 eq/100 g | 100 / 184.3 |
| Appearance (supplied grade) | Colourless liquid | Yellowing indicates ageing or acid contact |
| Purity (supplied grade) | 96.0% min | The balance is mainly the 1,2-diol and isomers – see the specification section |
| Solubility | Insoluble in water; miscible with most organic solvents | Hydrophobic tail dominates above C8 |
| Reactivity | Ring-opens with amines, acids, alcohols, thiols | The basis of every application below |
Two numbers in that table do all the work in formulation: EEW 184.3 g/eq and epoxy value 0.54 eq/100 g. They are the same information in two forms, and both are calculated rather than measured – if a supplier’s certificate quotes an epoxy value, check that it is consistent with 100/EEW before you build a formula on it.
How It Is Made
Terminal epoxyalkanes come from the corresponding 1-alkene by epoxidation of the double bond. Three routes appear in the literature and in commercial practice:
- Peracid epoxidation – the classical route. 1-dodecene reacts with a peroxycarboxylic acid (peracetic acid is the common choice) to give the epoxide plus the carboxylic acid, which is recycled. It is selective for the terminal double bond and is the route most associated with speciality alpha-olefin oxides.
- Hydrogen peroxide with a titanium silicalite catalyst (TS-1 type) – the cleaner industrial variant: H2O2 as the oxidant, water as the only stoichometric by-product, and no peracid handling. It is the technology direction for large-volume epoxides.
- In-situ peracid generation – hydrogen peroxide plus a carboxylic acid or anhydride in the reaction medium, used where peracid cannot be shipped or stored on site.
What all three have in common is the by-product problem that explains the specification: the epoxide ring can open under the reaction conditions, and every ring that opens becomes the 1,2-diol. The diol is not a poison – it is simply a molecule that carries no epoxide – so a 96% assay means roughly 4% of the product has already been converted to glycol or to positional isomers. This is normal for the alpha-olefin oxide family, and it is why these grades are sold at 95 to 99% rather than at the purities quoted for fine-chemical building blocks.
Specification: What 96% Actually Means
| Property | Specification | Interpretation |
|---|---|---|
| Appearance | Colourless liquid | Colour is the fastest ageing indicator – the epoxide ring opens to a diol, and trace acid accelerates it |
| Purity | 96.0% min | By GC. The balance is largely 1,2-dodecanediol and positional isomers, both of which are epoxide-free |
| Epoxy value | Consistent with 184.3 g/eq EEW | Ask for it by titration if the application is stoichiometric – GC purity and epoxy value are not the same measurement |
| Water | Low (typically 0.1 to 0.3% max) | Water plus acid opens the ring; specify a limit if the product is stored for months |
| Acidity | Negligible | Free acid is a ring-opening catalyst – the single most damaging impurity in this family |
| Colour (APHA or Gardner) | Low | Specify it for coatings and optical applications |
The point buyers miss: GC purity and epoxy value answer different questions. GC tells you how much of the peak is the epoxide; titration tells you how much reactive epoxide is actually in the drum. A batch can pass a 96% GC specification and still be low on epoxy value if part of the “96%” is a positional isomer that does not react at the expected rate. For stoichiometric use, buy on epoxy value.
Epoxy Equivalent Weight and the Cure Arithmetic
For an amine-cured system, the hardener weight per 100 g of resin is:
phr hardener = (amine equivalent weight x 100) / epoxy equivalent weight
For a blend, the mixture EEW is the reciprocal of the sum of the mass fractions divided by their individual EEW values. That single formula explains everything about using a monoepoxide as a diluent. Take a standard liquid DGEBA at EEW 185, add 20% of a C6 to C14 epoxide, and calculate:
| Diluent (20% with DGEBA EEW 185) | Diluent EEW | Blend EEW | DETA phr (amine eq. wt 20.6) | Effect on the network |
|---|---|---|---|---|
| 1,2-Epoxyhexane (C6) | 100.2 | 158.2 | 13.0 | Strong viscosity cut, large chain-termination penalty |
| 1,2-Epoxyoctane (C8) | 128.2 | 169.9 | 12.1 | Balanced |
| 1,2-Epoxydecane (C10) | 156.3 | 178.4 | 11.6 | Mild dilution |
| 1,2-Epoxydodecane (C12) | 184.3 | 184.9 | 11.1 | Almost no stoichiometry change |
| 1,2-Epoxytetradecane (C14) | 212.4 | 189.9 | 10.9 | Plasticising rather than diluting |
| 1,5-Hexadiene diepoxide (difunctional) | 57.1 | 127.7 | 16.1 | Crosslinks – opposite of a diluent |
Read the C12 row against the C6 row and the commercial argument is complete. Both cut viscosity, but C6 pulls the hardener requirement from 11.1 to 13.0 phr and terminates one chain per molecule, while C12 leaves the ratio effectively unchanged. The price you pay with C12 is that it dilutes less and that its long alkyl tail plasticises the network: expect a lower glass transition temperature and lower chemical resistance if the loading is high. With C6 the network is more highly crosslinked per unit mass of diluent but more chains are left dangling.
The difunctional row is the opposite tool. 1,5-Hexadiene diepoxide at EEW 57.1 is not a diluent at all – it raises the hardener demand steeply because it adds crosslinks, and it is used where you want higher reactivity and higher crosslink density at the cost of brittleness.
Where 1,2-Epoxydodecane Is Used
| Application | Role | Why the C12 chain |
|---|---|---|
| Reactive diluent in epoxy coatings and adhesives | Lowers viscosity, participates in cure | EEW close to the base resin, so cure ratio barely shifts |
| Acid scavenger (HCl absorber) in formulations and process streams | Consumes free acid by ring opening | Hydrophobic, low water solubility – stays in the organic phase |
| Chain terminator / molecular weight control | Caps one end of a growing polymer | Monoepoxide by design |
| Intermediate to 1,2-dodecanediol and amino alcohols | Hydrolysis or aminolysis of the oxirane | Gives a C12 hydrophobic diol or amino alcohol |
| Surfactant and lubricant intermediate | Hydrophobe after ring opening with amines or alcohols | C12 is the classic hydrophobe length |
| Stabiliser for chlorinated solvents and resins | Scavenges liberated HCl | Same scavenger role, in a low-water system |
The common thread is that C12 is chosen when you want a hydrophobic, low-volatility epoxide that reacts like a resin rather than like a solvent. The short-chain grades evaporate; the long-chain grades are waxy and slow to incorporate. C12 is the one that behaves like a liquid resin component.
Choosing Between the Homologues
Chain length controls four properties simultaneously – volatility, epoxide density, hydrophobicity and network flexibility – and they move in opposite directions, which is why the selection is not obvious:
| Property | C6 | C8 | C10 | C12 | C14 |
|---|---|---|---|---|---|
| Epoxy value (eq/100 g) | 1.00 | 0.78 | 0.64 | 0.54 | 0.47 |
| Volatility / odour | High | Moderate | Low | Very low | Negligible |
| Viscosity cut per 20% | Largest | Large | Moderate | Small | Minimal |
| Water resistance contribution | Low | Moderate | Good | Good | Best |
| Practical note | Workshop ventilation needed | General purpose diluent | Good compromise | Diluent that behaves like resin | Waxy; slow incorporation |
The full comparison, including the cyclic and difunctional members of the group, is in our chain-length selection guide for C6 to C14 alkyl epoxides.
Procurement Notes
| Item | What to specify |
|---|---|
| Assay basis | 96.0% min by GC, and the epoxy value by titration |
| Water | 0.1 to 0.3% max – state the limit you need, not the default |
| Acidity | Report free acid; it is the ring-opening catalyst |
| Colour | APHA limit if the end product is clear or light-coloured |
| Packaging | 160 kg or 180 kg steel drums, 25 kg cans for trials, HDPE for small quantities; nitrogen blanket where available |
| Documentation | Per-batch COA with GC purity and epoxy value, current SDS |
Two questions separate a real offer from a relabelled one: what is the epoxy value, and what is the water content. A supplier who answers both and adds the colour has a controlled process; a supplier who only quotes assay is selling a drum.
Safety, Handling and Storage
- Hazard profile: combustible liquid; causes skin and eye irritation; repeated skin contact can cause sensitisation. Epoxides are alkylating agents – treat all members of the family as potential sensitisers and avoid skin contact even when the label does not carry a sensitisation phrase.
- Ring-opening hazards: contaminated product (acid, base, amine, rust) can exotherm and polymerise in the container. Never return unused material to a drum, and never store it in a container that previously held an amine.
- Storage: sealed, cool, out of sunlight, away from acids, bases, amines and oxidisers. Nitrogen blanketing slows the diol formation that shows up as a drifting epoxy value.
- Materials: stainless steel and HDPE are suitable. Avoid galvanised or rusting steel (iron salts catalyse ring opening) and avoid contact with strong bases in storage.
- Regulatory position: an industrial monoepoxide, not a narcotic, drug substance or controlled precursor. Buyers confirm their own local registration and end-use requirements.
Frequently Asked Questions
Is 1,2-epoxydodecane the same as dodecene oxide?
Yes – 1,2-epoxydodecane, dodecene oxide, dodecylene oxide and 1,2-epoxy dodecane all refer to CAS 2855-19-8, the terminal epoxide of 1-dodecene.
Why is the assay only 96%?
Because the epoxide ring opens during manufacture and storage, giving the 1,2-diol and positional isomers that carry no epoxide. This is normal for the alpha-olefin oxide family; what matters for formulation is the epoxy value, not the GC peak alone.
Can I use it as a reactive diluent without changing my hardener ratio?
At moderate loadings, effectively yes – its EEW of 184.3 g/eq is nearly the same as a liquid DGEBA at 185, so a 20% addition moves the blend EEW to 184.9 and the hardener requirement hardly at all. But it still terminates chains, so expect a lower glass transition temperature.
What happens if water gets into the drum?
Water alone is slow, but water plus acid opens the ring to the diol, and the epoxy value falls. Keep bungs tight, avoid acid contamination, and re-test epoxy value if a drum has been open for months.
Do you supply the other chain lengths?
Yes – 1,2-epoxyhexane (C6), epoxyoctane (C8), epoxydecane (C10) and epoxytetradecane (C14) are supplied as part of the same series, along with the cyclic and difunctional epoxides in this group.
References and Disclaimer
- PubChem record for CAS 2855-19-8 – molecular formula C12H24O, molecular weight 184.32.
- Epoxy equivalent weights and epoxy values in this article are calculated from molecular weight and functionality; blend EEW values use the reciprocal mixing rule and the hardener phr values assume diethylenetriamine at 20.6 g/eq. Confirm against your own resin, hardener and cure schedule.
- Assay and appearance follow the current commercial specification for this grade.
Disclaimer: technical and commercial information for industrial buyers, not a specification or SDS. Handle according to the supplier’s current SDS and your local regulations.
PolyBlueChem supplies 1,2-epoxydodecane (CAS 2855-19-8) at 96.0% min as a colourless liquid, with per-batch COA reporting GC purity and epoxy value, in 25 kg cans to 180 kg drums. Tell us the application – reactive diluent, acid scavenger or diol intermediate – and the chain length you are comparing, and we will confirm the grade and the documentation. View the 1,2-epoxydodecane product page for the current specification.