Thionyl Chloride CAS 7719-09-7
Chelora Chemicals is a supplier of high-purity Thionyl Chloride, shipping worldwide to API manufacturers, agrochemical producers, dye works and battery chemical plants. Every consignment leaves with a batch-specific COA, the current SDS and full dangerous-goods documentation.
Also known as: SOCl2 · Thionyl dichloride · Sulphurous oxychloride · Sulphur oxychloride · TC
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Price, lead time and a sample COA for Thionyl Chloride, usually within one working day. We ship worldwide.
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- Batch-specific COA
- Safety Data Sheet (SDS)
- Technical Data Sheet
- Dangerous-goods papers (UN 1836)
- Certificate of origin
What is Thionyl Chloride?
Thionyl chloride is SOCl2 — a sulphur atom carrying one oxygen and two chlorines. It is the reagent synthetic chemists reach for when they need to replace a hydroxyl group with a chlorine and have the by-products leave as gases. Sulphur dioxide and hydrogen chloride both boil off, so the work-up is simply evaporation rather than filtration.
It is a colourless to pale yellow fuming liquid boiling at 74–76 °C, with a sharp, suffocating odour. It reacts violently with water, producing sulphur dioxide and hydrogen chloride, which makes moisture exclusion the single most important handling discipline around it — in storage, in transfer lines and in the reaction vessel.
Commercial material is often faintly yellow; a deepening colour usually signals dissolved sulphur or chlorine, or decomposition from moisture ingress. Distilled, low-colour grades exist for pharmaceutical and battery applications where that matters.
Commercially it is a mid-volume reagent with three distinct demand streams: synthesis of acid chlorides and alkyl chlorides for pharmaceuticals, agrochemicals and dyes; dehydration chemistry such as amide-to-nitrile conversion; and lithium thionyl chloride batteries, where it is the cathode material rather than a reagent.
Why thionyl chloride specifically
- Gaseous by-products. Both by-products leave as gases, so there is no salt to filter and no inorganic residue to remove. On scale, that simplicity is worth more than almost any yield advantage.
- Converts acids to acid chlorides reliably. The workhorse route to acid chlorides, which then acylate amines and alcohols in the next step — the backbone of a great many API syntheses.
- Dehydrates as well as chlorinates. Amides to nitriles, aldoximes to nitriles. One reagent covers two distinct transformations.
- Cheap relative to the alternatives. Oxalyl chloride and phosphorus reagents are cleaner or milder in specific cases, but thionyl chloride is the economical default on production scale.
How Thionyl Chloride is Manufactured
Thionyl chloride is made by bringing sulphur, chlorine and oxygen together in the right oxidation states. Two gas-phase routes dominate.
- Sulphur trioxide and sulphur dichloride. Sulphur trioxide is reacted with sulphur dichloride to give thionyl chloride and sulphur dioxide. The principal commercial route.
- Sulphur dioxide and chlorine. Sulphur dioxide is chlorinated in the presence of a catalyst, typically activated carbon, to give thionyl chloride directly.
- By-product control. Sulphuryl chloride, sulphur monochloride and dissolved chlorine and sulphur are the recurring impurities. Each has a different consequence downstream, so they are quantified separately rather than lumped together.
- Fractional distillation. The product is purified by distillation under dry conditions. Low-colour and battery-grade material is distilled harder and filled under strict moisture exclusion.
Typical Commercial Specification
Figures below are representative of standard commercial grade. Pharmaceutical, low-colour and battery grades with tighter limits are available — send us the specification you work to and we will quote against it.
| Parameter | Typical Value |
|---|---|
| Appearance | Clear colourless to pale yellow fuming liquid |
| Assay | 99.5% min |
| Sulphuryl chloride (SO2Cl2) | 0.3% max |
| Free sulphur | 0.02% max |
| Free chlorine | 0.05% max |
| Sulphur monochloride | 0.1% max |
| Colour (APHA) | 50 max |
| Non-volatile residue | 0.02% max |
| Iron (Fe) | 5 ppm max |
| Distillation range | 74 – 76 °C |
| Density at 20 °C | 1.630 – 1.640 g/cm³ |
Physical & Chemical Properties
| Property | Value |
|---|---|
| Molecular formula | SOCl2 |
| Molecular weight | 118.97 g/mol |
| Appearance | Colourless to pale yellow fuming liquid |
| Odour | Sharp, suffocating, pungent |
| Melting point | approx. −105 °C |
| Boiling point | approx. 74 – 76 °C at 760 mmHg |
| Relative density | approx. 1.63 g/cm³ at 20 °C |
| Vapour pressure | approx. 12 kPa at 20 °C |
| Flash point | Not flammable; does not sustain combustion |
| Reaction with water | Violent — hydrolyses to sulphur dioxide and hydrogen chloride |
| Solubility | Miscible with benzene, toluene, chloroform and most dry aprotic solvents |
| Decomposition | Decomposes above about 140 °C to sulphur dioxide, chlorine and sulphur monochloride |
| Incompatibilities | Water, alcohols, amines, strong bases, ammonia, dimethyl sulphoxide, metals in the presence of moisture |
| Decomposition products | Sulphur dioxide, hydrogen chloride, chlorine, oxides of sulphur |
Reactivity in practice
A reagent that delivers chlorine and leaves as gas. Four transformations account for most of the demand:
- Carboxylic acids to acid chlorides. The headline reaction. The acid chloride is then used immediately to acylate an amine or an alcohol, typically without isolation.
- Alcohols to alkyl chlorides. Primary and secondary alcohols are converted cleanly, with stereochemical outcome depending on conditions and on whether a base such as pyridine is present.
- Amides and aldoximes to nitriles. Dehydration rather than chlorination — the same reagent, a different transformation.
- Violent hydrolysis. Contact with water gives sulphur dioxide and hydrogen chloride rapidly and exothermically. This is the governing safety and handling fact about the product.
- Battery cathode chemistry. In lithium thionyl chloride cells it is the cathode material and the electrolyte solvent, which is why battery-grade purity specifications look nothing like synthesis-grade ones.
Thionyl Chloride vs the Other Chlorinating Agents
Several reagents convert an acid to an acid chloride. The choice comes down to by-product handling, substrate sensitivity and cost, and on production scale by-product handling usually wins.
| Reagent | CAS | By-products & when it is preferred |
|---|---|---|
| Thionyl Chloride | 7719-09-7 | SO2 and HCl, both gases — the economical production-scale default |
| Oxalyl Chloride | 79-37-8 | CO, CO2 and HCl — milder and cleaner for sensitive substrates, markedly more expensive |
| Phosphorus Trichloride | 7719-12-2 | Phosphorous acid — a liquid residue to separate; cheap but messier on work-up |
| Phosphorus Pentachloride | 10026-13-8 | POCl3 — vigorous, used where thionyl chloride is too mild |
| Chloroacetyl Chloride | 79-04-9 | Not a chlorinating agent — an acylating reagent, often made using thionyl chloride |
Stated plainly: thionyl chloride wins on work-up. Phosphorus reagents leave a liquid or solid phosphorus residue that has to be separated, and oxalyl chloride does the same job more gently at several times the price. For a plant running tonnes rather than grams, a reaction whose by-products simply leave through the scrubber is worth a great deal.
Industries We Supply Thionyl Chloride To
The same fuming liquid goes to an API plant, a herbicide works and a battery line. What changes between them is the grade, the colour and impurity limits, and the dangerous-goods paperwork each destination expects.
Where Thionyl Chloride is Used
Thionyl chloride is a reagent rather than a building block — it rarely ends up in the product. These are the end uses our customers buy it for.
In acid chloride chemistry
The standard sequence is to treat the carboxylic acid with a slight excess of thionyl chloride, often with catalytic dimethylformamide, drive off the sulphur dioxide and hydrogen chloride, strip the excess reagent and use the crude acid chloride directly. Because the reagent itself is volatile and the by-products are gases, the crude product is often clean enough to carry forward — which is precisely why the route survives at scale despite the handling demands.
In dehydration and nitrile formation
Primary amides dehydrate to nitriles under thionyl chloride, as do aldoximes. This matters in API routes where a nitrile is the gateway to an amine, a tetrazole or a heterocycle. The reaction is more sensitive to moisture and to temperature than acid chloride formation, so feedstock water content and reagent purity show up more visibly in the result.
In battery manufacture
Lithium thionyl chloride cells use the material as both cathode and electrolyte solvent, which gives it a completely different specification profile: moisture, iron and free chlorine are controlled far more tightly than any synthesis application would require, because they affect cell life and self-discharge rather than reaction yield. Battery grade is a distinct commercial product, not standard material with a better certificate.
Need thionyl chloride to a pharmaceutical or battery specification?
Tell us the assay, sulphuryl chloride and colour limits you work to, your packing preference and the annual quantity. We will come back with a price, a lead time, a sample COA and the Class 8 documentation.
Quality Control & Testing
Every lot is released against a batch-specific Certificate of Analysis. The methods behind the numbers are standard across the industry, and we are happy to share them or to work to your own in-house test protocol.
- Assay and impurity distribution — quantifying sulphuryl chloride, sulphur monochloride, free sulphur and free chlorine alongside the main component.
- Colour — APHA / Hazen against a standard. The fastest indicator that a drum has seen moisture, light or warmth.
- Non-volatile residue — the figure that predicts fouling and residue in your vessel after the reagent is stripped off.
- Iron and trace metals — relevant in pharmaceutical service and critical in battery grade.
- Distillation range and density — quick identity and purity confirmations.
- Moisture-sensitive sampling — samples are drawn and sealed under dry conditions, because a sample handled in open air stops representing the drum within minutes.
Common Process Problems & Likely Causes
When thionyl chloride causes trouble in a plant, the cause is usually one of a short list of things. This table is the shortcut our technical desk works through before anyone opens a complaint file.
| Symptom | Likely cause | What to check |
|---|---|---|
| Material darker than expected on arrival | Moisture ingress, light or warmth in transit, or dissolved sulphur and chlorine | Seal integrity, colour on the COA, storage and transit conditions |
| Vigorous gassing and pressure on opening a drum | Moisture ingress reacting with the contents to give SO2 and HCl | Vent carefully in a controlled area; check seal and liner before use |
| Acid chloride yield below the qualification batch | Water in the substrate or the solvent consuming reagent | Karl Fischer on the substrate and solvent; charge calculation on true assay |
| Unexpected chlorinated by-products | Sulphuryl chloride content chlorinating where the substrate is sensitive | Sulphuryl chloride figure on the COA against your qualification lot |
| Corrosion of transfer lines and fittings | Moisture present in the system, making the contents aggressively corrosive to steel | Line dryness, nitrogen purge discipline, materials of construction |
| Residue in the vessel after stripping | Non-volatile residue above specification, or sulphur deposition | Non-volatile residue and free sulphur on the COA |
| Battery cell self-discharge out of specification | Trace iron or moisture at levels irrelevant to synthesis but critical to cells | Battery-grade specification rather than standard grade |
Packaging, Storage & Shipping
- Standard packing. 250 kg net in lined MS drums, with ISO tank containers arranged where volumes justify them.
- Moisture exclusion. This is the governing handling rule. Keep drums sealed, purge transfer lines with dry nitrogen, and never leave a container open to humid air. Moisture ingress both degrades the product and makes it corrosive to the container.
- Storage. Cool, dry, well-ventilated and bunded, out of direct sun, away from water, alcohols, amines, bases and oxidising agents.
- Materials of construction. Dry mild steel and glass-lined equipment are standard; PTFE for seals and gaskets. Avoid anything that admits moisture, and avoid rubber and most elastomers.
- Venting. Drums can develop pressure if moisture has entered. Open in a controlled area with the correct PPE and vent carefully, pointing the closure away from the operator.
- Scrubbing. Any transfer or reaction generates sulphur dioxide and hydrogen chloride. Caustic scrubbing on the vent system is not optional.
- Shelf life. Typically 12 months in unopened original packing under those conditions. Beyond that, re-test assay and colour rather than assume.
- Transport classification. Shipped under UN 1836, Thionyl chloride, Class 8, Packing Group II. Confirm against the current SDS and the shipper's declaration for your destination and mode.
Hazards & Safe Handling
Thionyl chloride causes severe skin burns and eye damage, is toxic by inhalation and reacts violently with water to release toxic and corrosive gases. It must be handled by trained personnel under a proper risk assessment, in equipment designed for it — the current SDS supplied with your consignment is the governing document.
- Water reactivity. The defining hazard. Contact with water — including moisture on skin, in air or in equipment — produces sulphur dioxide and hydrogen chloride rapidly and exothermically. Never use water on a spill or a fire involving this product.
- Inhalation. Vapour and the gases produced on hydrolysis are acutely toxic and severely irritant to the respiratory tract. Handle in a closed system under local exhaust ventilation with vent scrubbing.
- Skin and eye contact. Causes severe burns. Chemical-resistant gloves rated for acid chlorides, chemical goggles with a face shield, and chemical-resistant clothing. Contact with moist skin generates hydrochloric acid in situ.
- Emergency equipment. Safety shower and eyewash within immediate reach, and a respirator available for emergency intervention rather than routine work.
- Incompatibilities. Water, alcohols, amines, ammonia, strong bases, dimethyl sulphoxide and oxidising agents. The reaction with DMSO in particular can be violently exothermic.
- Spill response. Do not use water. Contain and absorb with dry inert non-combustible material such as dry sand or vermiculite, collect in a dry labelled container, and ventilate thoroughly.
- Environment. Hydrolyses rapidly in the environment to corrosive acids. Do not allow to enter drains, surface water or groundwater.
- First aid. Remove contaminated clothing immediately, brush off any dry material before flushing, then wash skin with plenty of water, flush eyes for at least 15 minutes and seek immediate medical attention with the SDS to hand.
Regulatory & Compliance Notes
Thionyl chloride is an established industrial chemical, a regulated dangerous good, and a scheduled chemical under the Chemical Weapons Convention. Because obligations differ by territory, volume and use, the notes below are orientation rather than legal advice — confirm your own position with your regulatory adviser before importing.
- Chemical Weapons Convention. Thionyl chloride is a CWC Schedule 3 chemical. Import, export and use attract declaration and licensing obligations in states party to the Convention, and end-use documentation is a routine part of every transaction.
- Inventory status. Listed on the principal chemical inventories in the major importing regions. Ask us for the inventory confirmation relevant to your destination country.
- Dangerous goods. UN 1836, Class 8, Packing Group II. Packing, marking, labelling and declarations prepared for IMDG (sea) or road freight as appropriate; air freight is generally not practical for this product.
- Import licensing. Several territories require a specific import licence or permit for this product rather than a general chemical registration. Start that process well before you need the material.
- End-use documentation. Expect to supply a statement of intended use and, in many jurisdictions, an end-user certificate. This is not optional paperwork for this product.
- Hazard communication. Supplied with an SDS compliant with the format applicable to your region, and labelled in line with the GHS classification for the product.
We Supply Thionyl Chloride Worldwide
Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Thionyl Chloride from India to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, dangerous-goods paperwork and freight so the material arrives ready to use.
- Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
- Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other Indian ports arranged where it suits the routing.
- Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the UN 1836 dangerous-goods declaration with any end-user certificate required issued as a complete set.
- Flexible volumes. A single drum for laboratory qualification, through LCL consolidations, up to ISO tank quantities on a supply contract.
- Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.
Buying Thionyl Chloride from Chelora
We are an independent sourcing and supply partner. For thionyl chloride that means settling two things at enquiry: the destination country, because the Chemical Weapons Convention paperwork drives the lead time, and whether your application is synthesis or battery manufacture, because the specifications barely overlap.
- Documentation on every lot. Batch-specific COA including sulphuryl chloride, free sulphur, free chlorine and colour, current SDS and TDS.
- Samples before commitment. Trial quantities for process qualification ahead of a commercial order, packed to exclude moisture.
- Quantities. From a single 250 kg drum through to ISO tank quantities on contract supply.
- Regulatory handling. CWC Schedule 3 declarations, end-user certificates and import licence guidance for your destination.
- Export experience. Class 8 dangerous-goods documentation, packing and labelling handled for sea and road freight.
- Related reagents. Chloroacetyl chloride, ethyl chloroformate and the wider pharmaceutical intermediate range from one supplier.
How ordering works
- Send the enquiry. Product, grade or pharmacopoeia standard, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
- We quote. Price, lead time, packing and a sample COA, normally within one working day.
- Sample and qualify. For first orders or critical applications, we send a trial quantity so your lab can sign off before you commit.
- Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
- Production and QC. Material allocated and released against a batch-specific COA, with a pre-shipment sample where the application calls for it.
- Ship and document. Packed, labelled and loaded with the full export document set, and tracked through to arrival.
Thionyl Chloride — Common Questions
The questions our technical desk is asked most often about Thionyl Chloride. If yours isn't here, call or email and you will reach someone who knows the chemistry.
What is the CAS number of Thionyl Chloride?
The CAS number for Thionyl Chloride is 7719-09-7, and its EC number is 231-748-8. It is also listed as thionyl dichloride, sulphurous oxychloride and SOCl2. The molecular weight is 118.97 g/mol and it boils at about 74 to 76 °C.
What is thionyl chloride used for?
Mainly for converting carboxylic acids to acid chlorides and alcohols to alkyl chlorides in pharmaceutical, agrochemical and dye synthesis, and for dehydrating amides and aldoximes to nitriles. Outside synthesis it is the cathode material and electrolyte solvent in lithium thionyl chloride batteries.
Do you supply thionyl chloride worldwide?
Yes, subject to the licensing that applies to a Chemical Weapons Convention Schedule 3 chemical. We supply across Asia Pacific, Europe, the Middle East, Africa and the Americas as well as throughout India, quoting on EXW, FOB, CIF, CFR and DAP terms, and handle the full export, dangerous-goods and end-use document set. Tell us the destination country early, because the paperwork usually sets the lead time.
Why is thionyl chloride preferred over other chlorinating agents?
Because its by-products are gases. Sulphur dioxide and hydrogen chloride simply leave through the scrubber, so there is no phosphorus residue to separate and often no need to isolate the acid chloride at all. Oxalyl chloride is gentler and cleaner for sensitive substrates but costs several times as much, which is why thionyl chloride remains the production-scale default.
What happens if thionyl chloride contacts water?
It hydrolyses violently, producing sulphur dioxide and hydrogen chloride. This is the governing safety fact about the product: never use water on a spill or fire involving it, keep transfer lines dry and nitrogen-purged, and expect pressure in any drum that has admitted moisture. It is also why the material becomes aggressively corrosive to steel once water is present.
Why did my drum build up pressure?
Almost always moisture ingress. Water reacting with the contents generates gas inside a sealed container. Open such a drum carefully in a controlled, well-ventilated area with full PPE, pointing the closure away from you, and check the seal and liner before using the material.
How is thionyl chloride manufactured?
Principally by reacting sulphur trioxide with sulphur dichloride, or by chlorinating sulphur dioxide over an activated carbon catalyst. Both leave a characteristic impurity tail — sulphuryl chloride, sulphur monochloride, free sulphur and free chlorine — which is why those figures appear on the certificate separately rather than being folded into assay.
What purity does Chelora supply, and can you meet a tighter specification?
Standard commercial grade is 99.5% minimum assay, with sulphuryl chloride held to 0.3%, free sulphur to 0.02%, free chlorine to 0.05%, colour to 50 APHA and non-volatile residue to 0.02% maximum. Pharmaceutical, low-colour and battery grades with tighter limits are available — send us the specification you work to.
Why does sulphuryl chloride content matter?
Because it chlorinates differently. Sulphuryl chloride is a ring and side-chain chlorinating agent, so where your substrate is sensitive it can produce chlorinated by-products you did not design for. If you are seeing unexpected chlorination, compare the sulphuryl chloride figure against your qualification lot before looking anywhere else.
Is thionyl chloride a controlled chemical?
Yes. It is a Schedule 3 chemical under the Chemical Weapons Convention, so import, export and use carry declaration and licensing obligations in states party to the Convention. An end-user certificate and a statement of intended use are a routine part of every transaction, and the licence is usually what determines the delivery date.
How should thionyl chloride be stored?
Cool, dry, well-ventilated and bunded, out of direct sun, with drums tightly sealed and away from water, alcohols, amines, bases and oxidising agents. Use dry mild steel or glass-lined equipment with PTFE seals, and purge transfer lines with dry nitrogen. Unopened original packing typically carries a 12-month shelf life.
What are the hazards of handling it?
It causes severe skin burns and eye damage, is toxic by inhalation, and reacts violently with water to release toxic and corrosive gases. Handle in a closed system under local exhaust ventilation with caustic vent scrubbing, with gloves, goggles, face shield and chemical-resistant clothing, and with safety shower and eyewash within immediate reach. Always work from the current SDS.
How is it classified for transport?
Under UN 1836, Thionyl chloride, Class 8 corrosive, Packing Group II. We prepare the packing, marking, labelling and declarations for sea and road freight; air freight is generally impractical for this product. Confirm the classification against the current SDS for your destination and mode.
What packing sizes and order quantities are available?
Standard packing is 250 kg net in lined MS drums, with ISO tank containers arranged where volumes justify them. Orders run from a single drum for trial work up to tank quantities on contract supply.
Ready to source Thionyl Chloride?
Send us your specification, grade and annual volume. You will get a price, a realistic lead time and a sample COA from someone who understands what the material has to do in your process — delivered anywhere in the world.