Dimethyl Sulfate
Dimethyl sulfate is the industrial world's default way to put a methyl group where it wasn't before — on an oxygen, a nitrogen or a sulfur atom, cleanly and in high yield, which is exactly why it has stayed the standard reagent for seven decades of dye, pharmaceutical and agrochemical synthesis.
Chelora Chemicals supplies dimethyl sulfate to dye, pharmaceutical, agrochemical and fine-chemical producers worldwide, in UN-approved packing, with a batch COA and GHS safety data sheet on every consignment.
Product identity
- CAS Number
- 77-78-1
- IUPAC name
- Dimethyl sulfate
- Molecular formula
- C₂H₆O₄S
- Molecular weight
- 126.13 g/mol
- EC / EINECS
- 201-058-1
- UN Number
- 1595 · Class 6.1
- SMILES
- COS(=O)(=O)OC
- HS Code
- 2920 90*
* Confirm the exact HS heading with your customs broker — esters of inorganic acids can sit under a different subheading depending on the destination tariff schedule.
What Dimethyl Sulfate is used for
Dimethyl sulfate is a colorless, oily liquid with a faint onion-like odor, carrying two methyl groups attached through a sulfate ester linkage. Both methyls are available for transfer to a nucleophile, which is precisely what makes the molecule commercially valuable — and why it is handled with the same seriousness as any other potent alkylating agent.
Its largest use is as a general-purpose methylating agent: methylating phenols and amines in dye and pigment intermediate synthesis, building methoxy groups into pharmaceutical and agrochemical actives, and quaternizing amines for surfactant and specialty-chemical production. Where a methyl ether or a methylated amine is the target, dimethyl sulfate is usually the most economical industrial route.
Where it sits among methylating agents
- Dimethyl sulfate (this product) the most cost-effective bulk methylating agent; two methyls transferred per molecule.
- Methyl iodide a more reactive but far more expensive alternative, generally reserved for smaller-scale or specialty synthesis.
- Dimethyl carbonate a greener, less acutely hazardous methylating agent increasingly specified where regulation favours it, at a yield and rate trade-off.
- Diethyl sulfate the ethylating equivalent of this reagent, used where an ethyl rather than a methyl group is the target. See that page.
On a potent alkylating agent, confirm the CAS number and handling protocol on your purchase order — see the full alkylating-agent range.
Appearance and handling character
The material ships as a colorless to pale yellow, oily liquid, practically insoluble in cold water but hydrolysing slowly to methanol and sulfuric acid, faster as temperature rises. It is classified as a suspected human carcinogen and a potent alkylating agent, toxic by all exposure routes including skin absorption, and its vapor is heavier than air. The safety section below should be read before any handling is planned.
| Parameter | Typical value |
|---|---|
| Appearance | Colorless to pale yellow oily liquid |
| Assay | 99.0% min |
| Acidity (as H2SO4) | 0.05% max |
| Color / APHA | Reported per batch |
| Moisture | Reported per batch |
Important: the figures above are indicative of commercial-grade material and are offered for planning only. The batch certificate of analysis is the governing document. Assay and acidity are the figures that most affect methylation yield — tell us your target and we will quote against it.
| Property | Value |
|---|---|
| Physical state | Oily liquid at ambient |
| Melting point | − 32 °C |
| Boiling point | 188 °C @ 760 mmHg |
| Density | 1.33 g/cm³ @ 20 °C |
| Water solubility | Slightly soluble; hydrolyses slowly |
| Vapor density | Heavier than air |
Physical constants compiled from public reference data for CAS 77-78-1 and rounded for readability. Treat them as orientation, not as a specification.
Where our customers put this reagent to work
This is a workhorse alkylating agent. The interest is always in what the methyl group becomes once it transfers.
Dye & pigment intermediate methylation
Methylation of phenolic and amino dye intermediates to build methoxy and N-methyl functionality into the finished colourant structure.
- Dye and pigment intermediate routes
- Colour-critical specification on request
- See our dye intermediate range
Pharmaceutical & agrochemical synthesis
O- and N-methylation steps appear throughout active pharmaceutical ingredient and crop-protection chemical synthesis, where DMS remains the most economical bulk reagent.
- API and agrochemical intermediate routes
- End-use declaration required
- Technical desk review of your route
Quaternary ammonium compounds
Quaternization of tertiary amines with dimethyl sulfate gives quaternary ammonium salts used as surfactants, phase-transfer catalysts and fabric softeners.
- Surfactant & specialty-chemical synthesis
- Custom synthesis quantities available
- Technical support for your route
Methyl ether synthesis
Converting a phenol or alcohol to its methyl ether is a routine step across fine-chemical manufacture, with DMS as the standard bulk reagent.
- Fine chemical intermediate routes
- Full impurity profile on request
- Laboratory grade available
Research & laboratory methylation
Small-scale methylation in process development and analytical derivatization, handled under the same strict controls as plant scale.
- Small DG-compliant packs
- Full analytical documentation available
- Reference-grade material on request
Contract & scheduled supply
Dye, pharma and agrochemical plants consume this reagent on a fixed schedule. We hold inventory and release it against your production calendar.
- Annual contracts with scheduled call-off
- Price held across the contract period
- Second source held in reserve
How we supply Dimethyl Sulfate
Chelora Chemicals is a supplier and sourcing partner, not a manufacturer. On a reagent classified as a suspected human carcinogen, owning no plant means we are never selling you whatever a captive unit happens to be running — we route your order to the producer whose packaging and documentation actually matches a controlled handling protocol.
We place your order with whichever qualified producer best matches your assay, your specification, your price point and your delivery window.
We keep a second qualified source on this line. When a plant goes down for maintenance, your order switches source rather than stalling.
- Assay and acidity confirmed before we quote. 99% min with low free acidity is the commercial standard — we state both figures on the COA.
- Carcinogen classification stated up front. We say so at enquiry stage, every time, so your EHS team can plan engineering controls before the first drum arrives.
- Batch COA shared before dispatch. You approve assay and acidity against your own spec while the material is still in our warehouse.
- Skin absorption flagged explicitly. Dimethyl sulfate is absorbed through intact skin — we state this so your controls target the actual exposure route.
- Pre-shipment samples for qualification. New account or new source, your laboratory runs a trial before the full quantity ever moves.
- Export machinery handled in-house. UN 1595 classification, approved packing, labelling, freight booking and customs paperwork are ours to manage.
Packed the way your plant receives it
Pack format drives your landed cost and your handling effort. Tell us how the material will be charged at your end and we will quote the format that suits your operation.
Lined steel / HDPE drums
UN-approved, lined drums for Class 6.1 liquids — the standard commercial format and the easiest for closed-system charging.
ISO / flexitank containers
Bulk ISO tank or flexitank movement for continuous-consumption plants, reducing drum handling and its exposure risk.
Road tanker (regional)
Dedicated tankers for domestic and cross-border delivery where receiving infrastructure exists at both ends.
Trial / sample quantities
Small, DG-compliant containers dispatched so your R&D team can qualify the grade before committing to larger volumes.
Incoterms to suit you
Quoted on the Incoterm your purchasing team works to, with DG documentation filed before the booking is made.
Campaign despatch
We hold contracted tonnage and release it against your production calendar instead of landing it all at once.
Skin absorption is the controlling route
Dimethyl sulfate is toxic by the oral, dermal and inhalation routes, absorbed through intact skin, and classified as a suspected human carcinogen with mutagenic and reproductive-toxicity concerns. The summary below is orientation only — the safety data sheet supplied with your consignment is the authoritative document.
Classified hazards
H301 + H331Toxic if swallowed or if inhaled.H310Fatal in contact with skin.H314Causes severe skin burns and eye damage.H350May cause cancer.H341Suspected of causing genetic defects.H411Toxic to aquatic life with long lasting effects.
Hazard statements reflect classifications commonly published for CAS 77-78-1. Methylating agents of this class present a delayed-presentation risk — a casualty who feels well immediately after exposure may still develop symptoms some hours later; the SDS and medical guidance should be followed regardless of initial presentation. Always read the SDS issued with your specific batch.
Spill & emergency orientation
Plan your response before the pallet arrives. Sections 4, 5 and 6 of the SDS are the authoritative instructions and should be posted at the point of use.
- Contain, do not hose to drain. H411 applies — collect spilled liquid with inert absorbent and dispose of it as regulated chemical waste.
- Assume skin absorption. Contaminated clothing is a continuing exposure route — remove it immediately and wash the skin thoroughly with soap and water.
- Expect delayed presentation. Symptoms from significant exposure can appear hours later — any exposed person should be medically assessed promptly, with the SDS in hand, even if they feel well.
- Ventilate and avoid vapor inhalation. Vapor is heavier than air and will accumulate in low-lying or enclosed spaces — ventilate before re-entry.
- Decontaminate equipment thoroughly. Residual DMS on tools or surfaces remains hazardous until fully neutralised and rinsed.
Storage
- Cool, dry, well-ventilated, access-controlled store. Away from direct sunlight and heat sources; elevated temperature accelerates hydrolysis and vapor generation.
- Keep containers tightly closed. On a sealed and bunded floor — vapor escape is a genuine and serious exposure route on this product.
- Segregate from amines, ammonia and strong bases. These react readily with dimethyl sulfate, some combinations violently.
- Restrict access and log entry. With a carcinogen classification, controlling who enters the store is a core control measure, not an optional one.
- Shelf life typically 12–24 months. In sealed original packing, away from heat. Re-assay before use after extended storage.
Handling & PPE
- Design skin and vapor contact out. Closed transfer, contained charging and local exhaust ventilation first; PPE last, never as the sole control.
- Chemical-resistant gloves, coveralls and face shield. With contaminated clothing removed, bagged and handled as contaminated waste rather than sent to an ordinary laundry.
- Respiratory protection for vapor. Organic-vapor cartridge respirators or supplied air during any operation that can generate vapor, per your exposure assessment.
- Health surveillance for exposed workers. Given the carcinogen classification, your occupational health provider should define a monitoring programme for routine handlers.
- Never discharge to drain or watercourse. H411 applies — contain and dispose of as regulated chemical waste.
Transport
Dimethyl sulfate moves as regulated cargo under UN 1595, Class 6.1. We classify each consignment, apply UN-approved packaging and labelling, and file the dangerous-goods declaration before the booking is made — ask us for the current DG paperwork when you plan the shipment.
What travels with every consignment
A chemical shipment is only as good as the file that travels with it. Verifying what the source plant sends is precisely the work you are buying from a supplier.
Certificate of Analysis
Batch-specific assay, acidity and moisture — checked against your purchase specification before release.
GHS Safety Data Sheet
Full 16-section SDS in GHS format covering hazards, exposure controls, handling, storage, spill response, toxicology and disposal, issued in the language your destination requires.
Dangerous Goods Declaration
UN 1595, hazard class and IMDG or RID/ADR declaration prepared and filed before the container is booked, with correctly marked and labelled packaging.
Certificate of Origin
Chamber-attested where required, plus preferential-origin forms where a trade agreement gives your import duty relief.
Third-party inspection
SGS, Intertek or Bureau Veritas sampling and inspection arranged on request before loading, giving you independent verification of what actually ships.
Retained & pre-shipment samples
Pre-shipment samples carry the same COA as the commercial lot, so what your laboratory qualifies is exactly what arrives.
Two methyl groups, one sulfate ester
Both methyl groups in dimethyl sulfate are electrophilic and available for transfer to a nucleophile, which is the entire basis of its industrial value. The routes below are the general industrial pattern, not a process disclosure.
React methanol with SO3 or oleum
Methanol reacts with sulfur trioxide or fuming sulfuric acid to form the sulfate ester.
Distill and purify
Crude dimethyl sulfate is distilled to remove unreacted methanol, methyl hydrogen sulfate and sulfuric acid.
Transfer a methyl group to the nucleophile
In use, an amine, phenol or other nucleophile displaces methyl sulfate, taking up one methyl group and releasing methyl hydrogen sulfate.
Neutralise the spent acid co-product
The methyl hydrogen sulfate co-product is neutralised and worked up as part of standard process design.
Why assay and acidity carry through the whole route
On a methylating agent, small changes in purity change the methylation yield directly:
- Free acidity signals partial hydrolysis. Hydrolysed DMS has already given up methylating power to water, lowering effective strength per kilogram charged.
- Moisture accelerates further hydrolysis in storage. Which is why moisture is tracked on the COA even though it is a minor figure in absolute terms.
- Color darkening usually tracks acidity. A quick, practical read on batch quality before the full assay comes back.
- Stoichiometry is unforgiving on a two-methyl reagent. Under-dosing leaves unreacted substrate; over-dosing wastes reagent and complicates work-up.
That is why we quote against your written assay and acidity limits rather than a generic "technical grade", and why the batch COA is shared for approval before dispatch rather than sent with the invoice.
| Material | Downstream / use |
|---|---|
| Dimethyl sulfate CAS 77-78-1 — this product | Bulk O-, N- and S-methylation |
| Diethyl sulfate CAS 64-67-5 | Bulk O-, N- and S-ethylation |
| Dimethyl carbonate CAS 616-38-6 | Lower-hazard alternative methylating agent |
| Methyl iodide CAS 74-88-4 | Higher-reactivity, smaller-scale methylation |
We supply across this intermediate family — see the full intermediate range. Send the CAS number and we will confirm the correct material before quoting.
What actually moves the price of this product
Knowing what drives the quote helps you time a purchase and read whether an offer is realistic.
Methanol and sulfur feedstock
DMS is made from methanol and SO3/oleum, so both feedstock markets feed through to price on their own cycles.
- Methanol tracks the broader petrochemical market
- Sulfur/oleum cost follows the acid-plant cycle
- We flag feedstock-driven moves in the quote
Handling and regulatory compliance cost
Carcinogen classification brings storage, training and health-surveillance obligations that sit inside the delivered price wherever they apply.
- Handling obligations vary by jurisdiction
- We check destination rules before quoting
- Ask about documentation for your site
Freight and DG surcharges
Class 6.1 cargo carries a hazardous surcharge, and carriers increasingly restrict routing for carcinogen-classified liquids.
- Compare on landed cost, not ex-works
- DG space books out ahead of peak season
- We quote FOB, CIF, CFR or DDP as you prefer
Co-product and plant economics
Methylation-agent plants balance DMS output against sister products on the same line; a shift in sister demand affects your lead time.
- Ask us what the sister market is doing
- Contracted call-off smooths the exposure
- We hold a second qualified source
Source availability
A plant turnaround, environmental inspection or feedstock disruption can take capacity offline at short notice.
- We hold a second qualified source on this line
- Qualify the alternate before you need it
- Ask us about dual-source contracts
Alternative-reagent substitution pressure
Regulatory pressure toward lower-hazard methylating agents (such as dimethyl carbonate) shapes long-term capacity investment in DMS itself.
- We track substitution trends on your behalf
- Ask us whether an alternative suits your route
- Long-term contracts lock in supply either way
| If your end use is… | Specify |
|---|---|
| Dye / pigment methylation | 99% min assay, low acidity, colour-critical |
| Pharma / agrochemical intermediate | Full impurity profile, end-use declaration |
| Quaternary ammonium synthesis | Standard commercial grade |
| Laboratory / analytical derivatization | Small DG-compliant pack, full COA |
Not sure which column you are in? Describe what you make from it and our technical desk will recommend the grade — including telling you when a cheaper specification would do the job just as well.
Support that goes beyond shipping the drum
What our technical desk will do
- Confirm assay and acidity before anything else. On this reagent both figures decide methylation yield, and we settle them in the first reply.
- Be straight about the carcinogen classification. Suspected human carcinogen, skin-absorbed, toxic by all routes — stated at enquiry stage so your EHS team can plan engineering controls before the first delivery.
- Review your handling and ventilation setup. We ask about your transfer and charging method before the first drum moves, not after an exposure incident.
- Review your specification before it goes into a contract. So you are not locked into a purity no plant can consistently hit.
Regulatory & compliance notes
- Carcinogen handling obligations are jurisdiction-specific. Several regimes impose exposure monitoring, health surveillance and record retention for this class. Confirm what applies at your site before the first delivery.
- Import controls vary by destination. We check destination rules before quoting, not after you have raised the PO.
- Chemical inventory listings differ between regions. We will supply the identity data you need for that filing.
- Effluent and waste rules matter. Check your discharge consent against the material before introducing it to site.
None of the above is legal advice — your own regulatory affairs team owns the final compliance position for your import and your workplace. What we commit to is accurate product identity data, an honest statement of the hazard classification and complete documentation to work from.
From enquiry to delivered pallet
Send the specification
Product name or CAS 77-78-1, your assay and acidity requirement, quantity, pack preference and destination port.
Receive a firm quote
Pricing, lead time, packing and Incoterm confirmed in writing within 24 hours — our sourcing desk is staffed around the clock.
Qualify and approve
Sample dispatched if you are qualifying a new source. Batch COA shared for your approval before the material is released.
Ship and track
UN 1595 classification filed, DG freight booked, export documents issued, and the consignment tracked through transit and clearance to your plant.
What buyers ask us about Dimethyl Sulfate
What is dimethyl sulfate used for?
Is dimethyl sulfate a carcinogen?
Is it absorbed through the skin?
What purity do you normally supply?
How is it different from diethyl sulfate?
What is the minimum order quantity?
How should we store it?
Is this a dangerous good? What paperwork comes with it?
Do you manufacture this yourself?
Request pricing on Dimethyl Sulfate
Send your required assay, acidity limit, quantity, pack format and destination port. Our sourcing desk is available 24 hours a day, 7 days a week, and comes back with pricing, lead time and packing options — whether that is a single trial pack or a contracted programme for the year.