Di Methyl Sulfate
Di Methyl Sulfate — DMS — is the industry's default methylating agent. It installs a methyl group onto oxygen, nitrogen and sulfur nucleophiles more cleanly and more cheaply than most alternatives, and that single property underpins large parts of dye, agrochemical, pharmaceutical and specialty chemical manufacture.
Chelora Chemicals supplies DMS to accredited industrial manufacturers with an established process use, under strict end-use and handling controls, 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
- UN 1595
- SMILES
- COS(=O)(=O)OC
- HS Code
- 2920 90*
* Confirm the exact HS heading with your customs broker, and note that this product is subject to enhanced import screening in a number of jurisdictions.
What Di Methyl Sulfate is used for
Dimethyl sulfate is the diester of sulfuric acid and methanol, and its reactivity comes down to one thing: the two methyl groups are highly electrophilic and transfer readily onto almost any nucleophile that reaches them — a phenolate oxygen, an amine nitrogen, a thiolate sulfur. That reliable, high-yielding methylation is what makes it the reagent a process chemist reaches for by default when an O-, N- or S-methylation step is needed.
In practice DMS is a controlled industrial reagent: it is consumed on-site as a process input by manufacturers running a specific methylation step, rather than resold onward or held as general stock. We supply it exclusively to accredited industrial buyers with a documented, verifiable end use.
Why we ask for end-use detail before quoting
DMS carries a severe hazard profile discussed in full in the safety section below, and its reactivity is exactly what makes it useful and what makes it dangerous. Before we quote, our technical desk will ask for:
- The methylation step you are running, so we can confirm DMS is the right reagent — in some routes a safer alkylating agent such as dimethyl carbonate can do the same job with a materially better safety profile.
- Your site's handling capability, including closed-transfer systems, fume extraction and emergency response arrangements, since these govern how the material should be packed and delivered.
- Your regulatory status as an industrial end-user, since import of this material is controlled or licensed in a number of jurisdictions.
If a lower-hazard alkylating agent would meet your process needs, we will say so — see our wider alkylating and sulfonating agent range for alternatives.
Appearance and handling character
DMS ships as a colourless to pale yellow, oily liquid with a faint onion- or garlic-like odour that is not a reliable warning of hazardous concentration — odour is detectable only well above levels that can already cause harm. It is only slightly soluble in water but hydrolyses slowly in it, releasing methanol and sulfuric acid; hydrolysis is much faster in warm or alkaline conditions. It is miscible with most common organic solvents. Read the next section before planning any handling: this material combines acute toxicity by every route of exposure with a carcinogenicity classification, and that should shape your controls from the outset.
| Parameter | Typical value |
|---|---|
| Appearance | Colourless to pale yellow oily liquid |
| Assay (GC) | 99.0% min |
| Moisture (KF) | 0.1% max |
| Acidity (as H2SO4) | 0.05% max |
| Colour (APHA/Pt-Co) | Reported per batch |
| Non-volatile residue | 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. If your process demands a tighter acidity limit or a specific moisture ceiling, send us the specification and we will quote against it.
| Property | Value |
|---|---|
| Physical state | Oily liquid at ambient |
| Melting point | ≈ −32 °C |
| Boiling point | ≈ 188 °C (decomposes) |
| Flash point | ≈ 83 °C (closed cup) |
| Relative density | ≈ 1.33 |
| Vapour pressure | ≈ 0.1 mmHg at 20 °C |
| Water solubility | Slight; hydrolyses on standing |
| Organic solubility | Miscible with most organic solvents |
| Odour | Faint, onion-like (not a reliable warning) |
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
DMS is a process reagent rather than a finished-product ingredient — it is consumed in a methylation step and does not usually appear, even as a trace, in the material that leaves the plant.
Dyes & pigment intermediates
DMS methylates phenolic and amino intermediates used to build dye chromophores, improving solubility, shifting shade and stabilising the final colourant against further reaction.
- O-methylation of phenolic dye intermediates
- N-methylation of amino dye precursors
- See our dye intermediate range
Agrochemical manufacture
A key methylating step in the synthesis of several herbicide, fungicide and insecticide active ingredients, where a methoxy or N-methyl group is required at a specific point in the molecule.
- Methoxy-group installation on aromatic rings
- N-methylation of heterocyclic intermediates
- See our agrochemical intermediate range
Pharmaceutical intermediates
Used under tightly controlled process conditions to install a methyl group at a specific position in an active pharmaceutical ingredient or intermediate, where alternative methylating agents may not give the required selectivity or yield.
- O- and N-methylation in multi-step synthesis
- Closed, engineered process use only
- Full traceability documentation supplied
Surfactant & specialty synthesis
Used in the manufacture of quaternary ammonium compounds and certain specialty surfactants, where methylation of a tertiary amine gives the quaternary structure the application requires.
- Quaternisation of tertiary amines
- Specialty surfactant synthesis
- Available for validated process use only
Fine chemical & laboratory synthesis
A standard methylating reagent in organic chemistry for research and process development, always supplied with the expectation of fume-hood handling and a documented risk assessment.
- Laboratory-scale methylation reactions
- Process development and scale-up studies
- Small-pack quantities available on request
Contract & scheduled supply
Established manufacturers running continuous or campaign methylation steps want tonnage released against a production plan under a fixed, audited handling protocol rather than as ad hoc deliveries.
- Annual contracts with scheduled call-off
- Agreed handling and packing protocol per site
- Second source held in reserve
How we supply Di Methyl Sulfate
Chelora Chemicals is a supplier and sourcing partner, not a manufacturer. We own no DMS plant — and for a reagent this hazardous, that independence works in your favour. We are never obliged to move volume simply because a captive unit produced it; we place your order only where the specification, the handling protocol and the end use genuinely line up.
We supply DMS exclusively to accredited industrial buyers with a verified business need and an established process use. This is a deliberate constraint, not an administrative formality: it is how the supply chain for a reagent this reactive stays accountable end to end.
We keep a second qualified source on this line for contracted customers, so a plant turnaround or a logistics disruption does not stall a validated production process that depends on continuous reagent supply.
- End use confirmed before any quote is issued. We ask what step you are running and how your site handles the material, and will recommend an alternative reagent if it would serve you better.
- Batch COA shared before dispatch. You approve the assay, moisture and acidity profile against your own spec while the material is still in our warehouse.
- Hazard status stated up front, in full. This material carries a carcinogenicity classification and acute toxicity by every exposure route, and we say so at the first enquiry — not in the small print of a document pack.
- Delivered only into confirmed closed-handling systems. We work with your engineering team to confirm receiving and transfer arrangements before the first delivery is scheduled.
- Packing chosen to minimise handling steps. Drums and small containers are sized and lined to reduce the number of times a container is opened and transferred manually.
- Export and import compliance handled in-house. Hazard classification, UN-approved packing, labelling, licensing checks, freight booking and customs paperwork are ours to manage.
- Full chain-of-custody documentation. Every consignment is traceable from source plant to your receiving dock, supporting your own regulatory and audit obligations.
Packed to minimise every point of contact
For a reagent this hazardous, pack format is a safety decision as much as a logistics one. We size and line every container to fit your closed-transfer system and to cut the number of manual handling steps to the minimum.
Sealed steel drums
UN-certified, gasket-sealed steel drums with closed-loop coupling fittings for direct pump transfer into your process vessel without opening the drum to atmosphere.
Dedicated ISO / road tankers
For contracted high-volume users with validated bulk receiving infrastructure, dedicated tank movement with closed coupling and vapour-return connections, arranged case by case.
Sealed laboratory & trial packs
Small, gasket-sealed containers for laboratory qualification and process development, dispatched only to buyers with a documented fume-hood handling capability.
End-use verification
Every order is matched to a declared, verifiable industrial end use before packing is finalised — this is a fixed part of our process for this product, not an optional step.
Incoterms to suit you
Quoted on the Incoterm your purchasing team works to. Freight arranged end-to-end with dangerous-goods documentation and, where applicable, import licensing checks completed before booking.
Campaign despatch
Contracted volumes are held and released against your production calendar under an agreed handling protocol, rather than landed as one large, harder-to-manage delivery.
Handle this as a severe, multi-route hazard
This is the point on the page that matters most. Dimethyl sulfate is acutely toxic by inhalation, skin contact and ingestion, absorbed readily through intact skin, severely corrosive to eyes and skin, and carries a carcinogenicity classification. Its vapour is heavier than air, may not be reliably detected by smell until harmful levels are reached, and delayed-onset symptoms following inhalation are a recognised feature of overexposure. The summary below is orientation only — the safety data sheet supplied with your consignment is the authoritative document and must govern your risk assessment, engineering controls, PPE selection and emergency planning before this material is ever opened on your site.
Classified hazards
H350May cause cancer.H301Toxic if swallowed.H310Fatal in contact with skin.H330Fatal if inhaled.H314Causes severe skin burns and eye damage.H341Suspected of causing genetic defects.
Hazard statements reflect the harmonised GHS classification commonly published for CAS 77-78-1. Supplier classifications may differ in detail; always read the SDS issued with your specific batch, and treat the acute toxicity and carcinogenicity entries as the ones that shape every part of your control programme.
Spill & emergency orientation
This is not a material to be handled without a rehearsed emergency plan already in place. The points below are orientation for your emergency planners — sections 4, 5 and 6 of the SDS are the authoritative instructions and should be posted at every point of use, with trained responders identified before the first delivery arrives.
- Evacuate and ventilate first. Vapour is heavier than air and can travel and collect in low areas; clear the area and ventilate before any response begins, per your SDS.
- Only trained personnel in full protective equipment — including self-contained breathing apparatus — should approach a spill. This is not a task for general plant staff.
- Neutralise with dilute ammonia solution or another SDS-specified neutralising agent under controlled conditions; never simply wash a spill to a drain.
- Assume exposure has occurred even without obvious symptoms. Onset of respiratory symptoms can be delayed for hours after inhalation exposure — anyone potentially exposed needs urgent medical evaluation, symptomatic or not.
- Have the SDS with the casualty. The treating clinician needs the product identity, CAS number and exposure route immediately, given how time-critical management of a serious exposure can be.
- Record the exposure and the incident. For a classified carcinogen and acute-fatal-hazard material, most occupational regimes expect a formal exposure record — decide this in advance with your EHS function, not after an incident.
Storage
- Dedicated, access-controlled store, cool, dry and separate from general chemical storage, with mechanical ventilation and continuous vapour detection where feasible.
- Keep containers sealed and undamaged. DMS hydrolyses slowly in contact with moisture, and any container breach is both a chemical and an acute exposure risk.
- Segregate strictly from water, strong bases, amines, oxidisers and any nucleophile-rich material, since these are exactly the substances DMS is designed to react with.
- Bunded, chemically resistant flooring with contained drainage to a neutralisation point, never to open ground or a general effluent system.
- Restricted access to named, trained personnel only. For a material this hazardous, controlling who can physically reach the store is a core control, not an administrative nicety.
Handling & PPE
- Closed, engineered transfer is the only acceptable method. Pump-to-pump connections, local exhaust ventilation and vapour-return lines should eliminate open-container handling entirely — this is not a material to decant by hand.
- Full chemical-resistant suit, gloves and boots, plus a full-face respirator or supplied air are the baseline whenever a closed system must be broken for maintenance, sampling or connection changes.
- Never rely on odour as a warning. The faint smell is detectable only well above hazardous concentration, so engineering controls and, where used, vapour monitoring are the real safeguards.
- Health surveillance and exposure records should be established before this material is introduced to a site — your occupational health provider and EHS function own the programme design; we flag the classification and supply the SDS that programme is built on.
- Never discharge to drain or watercourse. Treat all wash-water and spill residue as regulated hazardous waste under your SDS-specified disposal route.
Transport
DMS moves as regulated dangerous cargo under UN 1595. We classify each consignment, apply UN-approved packaging and labelling, verify destination import controls, and file the dangerous-goods declaration before the booking is made. The applicable packing group is stated on your shipping documents and SDS — ask us for the current DG paperwork when you plan the shipment.
What travels with every consignment
For a reagent under this level of control, the paperwork is not an afterthought — it is the mechanism that keeps the entire supply chain accountable, from source plant to your receiving dock.
Certificate of Analysis
Batch-specific assay by GC, moisture by Karl Fischer, acidity and colour — checked against your purchase specification before we release the goods.
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 classification, packing group and IMDG/IATA/road declaration prepared and filed before the shipment is booked, with correctly marked and labelled packaging.
End-use declaration
A signed declaration of intended industrial use, retained on file, supporting your own regulatory obligations as well as ours.
Third-party inspection
SGS, Intertek or Bureau Veritas sampling and inspection arranged on request before loading, giving you independent verification of what actually ships.
Chain-of-custody records
Full traceability from source plant, through our warehouse, to your receiving dock — retained and available for your own audit and regulatory needs.
Why this reagent methylates so reliably
DMS's usefulness and its hazard come from the same feature: the methyl carbons attached to the sulfate group are highly electrophilic, so nucleophiles attack them readily under mild conditions. The pattern below is the general industrial picture, not a process disclosure.
The reactive centre
Each methyl group sits on an electrophilic carbon activated by the adjacent sulfate ester, making it a ready target for nucleophilic attack under mild, controlled conditions.
Nucleophile attacks
A phenolate, an amine or a thiolate displaces methyl sulfate as the leaving group, transferring a methyl group onto the nucleophile in a clean, high-yielding step.
Two methyls available
Each molecule of DMS can, in principle, deliver two methylations, which is part of what makes it so reagent-efficient compared with single-methyl alkylating agents.
Quench and isolate
Excess reagent and by-product methyl hydrogen sulfate are quenched and neutralised under controlled conditions before the methylated product is isolated and purified.
Why purity and moisture control the outcome
Because the reagent is so reactive, small amounts of the wrong impurity have an outsized effect on a methylation step:
- Residual moisture hydrolyses DMS in the drum before it ever reaches your reactor, wasting reagent and generating acidity that can interfere with a base-sensitive substrate.
- Free acidity in the incoming material signals hydrolysis has already begun, and can protonate a nucleophile before it has a chance to react.
- Colour and non-volatile residue point to degradation products that can carry through into a coloured or contaminated methylated product.
That is the reason we quote against your written specification, supply the batch COA for approval before dispatch, and recommend a closed, moisture-excluded storage and transfer system for every site we supply.
| Reagent | Typical trade-off |
|---|---|
| Dimethyl sulfate CAS 77-78-1 — this product | High reactivity and efficiency; severe acute toxicity and carcinogenicity classification |
| Methyl iodide CAS 74-88-4 | Very reactive; volatile and also classified as a serious health hazard |
| Dimethyl carbonate CAS 616-38-6 | Substantially lower toxicity; often needs higher temperature or catalyst |
If a lower-hazard alternative would meet your process requirement, our technical desk will say so before quoting DMS — see the full alkylating agent range for options.
What actually moves the price of this reagent
DMS is not a commodity with a screen price. Knowing what drives the quote and the availability helps you plan a purchase realistically.
Compliance cost dominates
The classification and controlled-supply status of this material mean compliance, documentation and verified-end-use screening add materially to cost compared with a general industrial chemical — and that cost is built into every quote.
- End-use verification takes time — plan ahead
- New accounts should expect an onboarding step
- Established accounts move faster on repeat orders
Feedstock economics
DMS is produced from methanol and sulfuric acid or sulfur trioxide, so movements in methanol and sulfur markets feed through to the reagent price over a quarter or so.
- Methanol price is the larger driver
- Energy cost weighs on the production step
- We flag feedstock-driven moves in the quote
Freight & DG surcharges
This is heavily regulated cargo, so freight carries a substantial hazardous surcharge and space is limited to carriers and routes cleared to move it. Landed cost is dominated by logistics, not by the ex-works price.
- Compare on landed cost, not ex-works
- DG-cleared routes and carriers are limited
- We quote FOB, CIF, CFR or DDP as you prefer
Pack format
Sealed drums with closed-loop coupling cost more per kilo than the same weight of a less hazardous chemical, but they materially reduce operator exposure — for this product that trade-off is worth making every time.
- Closed-loop fittings add cost but cut exposure
- Small packs suit qualification, not campaign volume
- We size packing to your actual handling system
Regulatory approval lead time
Some destinations require an import licence or end-use permit for this material before it can be shipped. Building that lead time into your production plan avoids a schedule surprise later.
- Check destination licensing requirements early
- We handle the checks, but the lead time is real
- Repeat orders on file move faster
Source availability
A plant turnaround or a regulatory inspection can take capacity offline. We hold a second qualified source on this line for contracted customers to avoid a single point of failure on a reagent your process depends on.
- Dual-source contracts available
- Qualify the alternate before you need it
- Ask our technical desk about contracted supply
| If your end use is… | Specify |
|---|---|
| Dye & pigment methylation | Standard 99% grade, colour ceiling as required |
| Agrochemical synthesis | High assay, tight acidity and moisture limits |
| Pharmaceutical intermediates | Tight impurity profile; full analytical pack |
| Laboratory / R&D | Small sealed pack, high purity, full COA |
Not sure which column you are in, or whether DMS is even the right reagent for your step? Describe the reaction to our technical desk and we will advise — including recommending a lower-hazard alternative where one would do the job.
Support that goes beyond shipping the drum
What our technical desk will do
- Confirm DMS is the right reagent. Tell us the methylation step you are running, and we will confirm whether DMS is genuinely the best fit or whether a lower-hazard alternative such as dimethyl carbonate would work equally well.
- Be completely straight about the hazard profile. We state the carcinogenicity and acute toxicity classification at the first enquiry, so your EHS team can assess feasibility before any commercial discussion goes further.
- Review your closed-handling system before the first delivery, working with your engineering team to confirm receiving, transfer and ventilation arrangements are adequate for this material.
- Review your specification before it goes into a contract, so you are not locked into a purity or acidity limit that adds cost without adding process value.
Regulatory & compliance notes
- Carcinogen and acute-toxicity obligations are jurisdiction-specific. Several regimes impose substitution review, exposure monitoring, health surveillance and record retention for material with this hazard profile. Confirm what applies at your site before the first delivery.
- Import is licensed or controlled in a number of jurisdictions. We check and, where required, obtain the necessary licence or end-use declaration before quoting a shipment — this is standard practice for this product, not an exception.
- Chemical inventory listings differ between regions. Confirm your obligations under the applicable inventory regime for your import volume — we will supply the identity data you need for that filing.
- Workplace exposure limits for this material are set very low in most regulatory regimes, reflecting its acute and chronic hazard profile — confirm the applicable limit for your jurisdiction with your occupational hygiene team.
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 giving you accurate product identity data, an honest and complete statement of the hazard classification, and full documentation to work from.
From enquiry to verified, delivered drum
Send the specification and end use
Product name or CAS 77-78-1, the methylation step you are running, quantity, pack preference, destination and your site's handling arrangements.
End-use and account verification
Our technical desk confirms DMS is the right reagent, reviews your handling capability and completes the standard end-use documentation for this product.
Receive a firm quote
Pricing, lead time, packing and Incoterm confirmed in writing once verification is complete — typically within a few working days for a new account.
Ship and track
DG classification and any required import licensing filed, freight booked, export documents issued, and the consignment tracked through transit and clearance to your plant.
Often discussed alongside this reagent
Our technical desk will point you to the best-fit reagent for your process, whether that is this product or an alternative. These are the related alkylating agents, sulfuric acid and derivatives our fine chemical, dye and agrochemical customers most often ask about — see the full range on our products page.
What buyers ask us about Di Methyl Sulfate
Is this material classified as a carcinogen?
Who can you sell this to?
Is there a safer alternative to DMS for methylation?
What purity do you normally supply?
What is the minimum order quantity?
How long does delivery take?
How should we store it, and what is the shelf life?
What happens if it contacts water?
Is this a dangerous good? What paperwork comes with it?
- Batch certificate of analysis
- GHS-format safety data sheet
- Dangerous-goods declaration with UN number, class and packing group
- End-use declaration and chain-of-custody documentation
- Commercial invoice, packing list and bill of lading or airway bill
- Any destination-specific import licence or permit
Do you supply to my country?
Do you manufacture this yourself?
Can you hold stock against a production plan?
Discuss your requirement for Di Methyl Sulfate
Tell our technical desk about the methylation step you are running, your site's handling capability, and your required quantity and destination. We will confirm whether DMS is the right reagent, verify your account, and come back with pricing, lead time and packing options for a controlled, documented supply.