Ethyl Chloroformate CAS 541-41-3
Chelora Chemicals is a supplier of high-purity Ethyl Chloroformate, shipping worldwide to API manufacturers, peptide and fine chemical producers and agrochemical plants. Every consignment leaves with a batch-specific COA, the current SDS and full dangerous-goods documentation.
Also known as: ECF · Ethyl carbonochloridate · Chloroformic acid ethyl ester · Ethyl chlorocarbonate · Carbethoxy chloride
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Price, lead time and a sample COA for Ethyl Chloroformate, 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 1182)
- Certificate of origin
What is Ethyl Chloroformate?
Ethyl chloroformate is ClCOOC2H5 — the ethyl ester of chloroformic acid, and effectively a tamed, liquid substitute for phosgene in one specific job: attaching an ethoxycarbonyl group. It reacts with amines to give carbamates, with alcohols to give carbonates, and with carboxylate salts to give mixed anhydrides.
It is a clear, colourless liquid boiling at 93–95 °C, with a sharp, suffocating odour and strong lachrymatory action. It is flammable, acutely toxic by inhalation, and hydrolyses on contact with water — a combination of hazards that places it in Packing Group I and shapes how it is shipped and handled.
Its most distinctive role is in peptide and amide coupling. Treating a carboxylic acid salt with ethyl chloroformate gives a mixed anhydride that is reactive enough to acylate an amine but selective enough to do so without the racemisation problems of harsher activating methods. That makes it a staple of fine chemical and API synthesis.
Commercially it is a specialty reagent rather than a bulk chemical. Demand comes from pharmaceutical synthesis, peptide chemistry, carbamate and carbonate manufacture, agrochemical intermediates, and analytical derivatisation, where it is used at laboratory scale to make amino acids and amines volatile enough for gas chromatography.
Why ethyl chloroformate specifically
- Mixed anhydride coupling with low racemisation. Activating a carboxylic acid as the mixed carbonic anhydride is mild enough to preserve stereochemistry, which is exactly what peptide and chiral API work needs.
- Clean by-products. The mixed anhydride route releases carbon dioxide and ethanol on coupling — nothing to filter out, unlike carbodiimide methods that leave a urea behind.
- A liquid stand-in for phosgene. It delivers the carbonyl in carbamate and carbonate chemistry without handling a toxic gas, which is why many plants chose it decades ago and never moved.
- Reliable ethoxycarbonyl protection. Protects an amine as the carbamate, stable through a range of conditions and removable when the route calls for it.
How ECF is Manufactured
Ethyl chloroformate is made by reacting ethanol with phosgene. There is no commercially significant alternative route, which is one reason the product carries the regulatory attention it does.
- Phosgenation of ethanol. Ethanol is reacted with phosgene under controlled conditions, giving ethyl chloroformate and hydrogen chloride. Temperature and feed ratio control the extent of over-reaction to diethyl carbonate.
- Hydrogen chloride removal. The by-product hydrogen chloride is stripped and scrubbed. Residual HCl in the product is a specification item because it catalyses further decomposition.
- By-product control. Diethyl carbonate and residual phosgene are the characteristic impurities. Residual phosgene in particular is controlled tightly, because it is far more hazardous than the product itself.
- Fractional distillation. Purified by distillation under dry conditions and filled with moisture excluded, since hydrolysis both degrades the product and raises its acidity.
Typical Commercial Specification
Figures below are representative of standard commercial grade. Pharmaceutical grades with tighter phosgene and acidity limits are available — send us the specification you work to and we will quote against it.
| Parameter | Typical Value |
|---|---|
| Appearance | Clear colourless liquid |
| Assay (GC) | 99.0% min |
| Diethyl carbonate | 0.5% max |
| Residual phosgene | 50 ppm max |
| Free HCl / acidity | 0.1% max |
| Ethanol | 0.2% max |
| Colour (APHA) | 20 max |
| Non-volatile residue | 0.01% max |
| Water (Karl Fischer) | 0.05% max |
| Boiling range | 92 – 96 °C |
| Density at 20 °C | 1.130 – 1.140 g/cm³ |
Physical & Chemical Properties
| Property | Value |
|---|---|
| Molecular formula | ClCOOC2H5 |
| Molecular weight | 108.52 g/mol |
| Appearance | Clear colourless liquid |
| Odour | Sharp, suffocating; strongly lachrymatory |
| Melting point | approx. −81 °C |
| Boiling point | approx. 93 – 95 °C at 760 mmHg |
| Flash point | approx. 16 °C (closed cup) — flammable |
| Relative density | approx. 1.135 g/cm³ at 20 °C |
| Vapour density | Heavier than air; vapour accumulates at low level |
| Reaction with water | Hydrolyses to ethanol, carbon dioxide and hydrogen chloride |
| Solubility | Miscible with most dry aprotic organic solvents; reacts with water and alcohols |
| Thermal stability | Decomposes on heating; avoid temperatures approaching the boiling point in storage |
| Incompatibilities | Water, alcohols, amines, strong bases, oxidising agents, dimethyl sulphoxide |
| Decomposition products | Hydrogen chloride, carbon monoxide, carbon dioxide, phosgene |
Reactivity in practice
A chloroformate delivers an alkoxycarbonyl group to whatever nucleophile it meets. Which product you get depends entirely on what you offer it:
- Amines to carbamates. Primary and secondary amines give ethyl carbamates — both as products in their own right and as protecting groups.
- Carboxylates to mixed anhydrides. A carboxylic acid salt gives the mixed carbonic anhydride, which then acylates an amine with low racemisation. The peptide chemist's standard move.
- Alcohols to carbonates. Alcohols give carbonate esters, used as intermediates and solvents.
- Analytical derivatisation. Converts amino acids and amines to volatile derivatives for gas chromatography — a small-scale but persistent use.
- Hydrolysis. Water gives ethanol, carbon dioxide and hydrogen chloride. Unwanted in process, and the reason dry handling discipline matters.
Ethyl Chloroformate vs the Other Chloroformates and Coupling Reagents
Chloroformates differ by their alkyl group, and coupling reagents differ by what they leave behind. Both comparisons matter when choosing between them.
| Reagent | CAS | What it delivers & when it is used |
|---|---|---|
| Ethyl Chloroformate | 541-41-3 | Ethoxycarbonyl — mixed anhydride coupling, carbamates, carbonates, GC derivatisation |
| Methyl Chloroformate | 79-22-1 | Methoxycarbonyl — similar chemistry with a smaller, more volatile reagent |
| Isobutyl Chloroformate | 543-27-1 | Isobutoxycarbonyl — often preferred for mixed anhydride peptide coupling, with a bulkier group |
| Benzyl Chloroformate | 501-53-1 | Cbz protection — the classic removable amine protecting group in peptide synthesis |
| Thionyl Chloride | 7719-09-7 | Not a chloroformate — converts acids to acid chlorides, a harsher activation route |
Stated plainly: within the chloroformate family the alkyl group decides steric bulk, volatility and whether the resulting carbamate is meant to stay or be removed later. Between families, the choice is about activation strategy — a mixed anhydride is milder and cleaner than an acid chloride, and leaves no urea behind the way a carbodiimide does.
Industries We Supply ECF To
The same clear liquid goes to a peptide plant, an API works and an analytical laboratory. What changes between them is the grade, the phosgene limit and the dangerous-goods paperwork each destination expects.
Where ECF is Used
Ethyl chloroformate is a reagent rather than a building block, and it is bought for three distinct jobs. These are the end uses our customers buy it for.
In mixed anhydride coupling
The sequence is standard across fine chemical synthesis: form the carboxylate salt with a tertiary base, add ethyl chloroformate at low temperature to give the mixed carbonic anhydride, then add the amine. The anhydride collapses on attack to release carbon dioxide and ethanol, leaving the amide. Its appeal over harsher activation is stereochemical — the method is mild enough to preserve chiral centres that an acid chloride route would compromise, and it leaves no urea by-product to filter out.
In carbamate and protecting group chemistry
Amines react directly to give ethyl carbamates. Sometimes the carbamate is the target — several agrochemical and pharmaceutical actives contain one — and sometimes it is a protecting group installed to let chemistry happen elsewhere on the molecule. Either way the step is clean and the reagent is cheap relative to the specialist protecting-group reagents.
In analytical and laboratory use
Derivatisation with ethyl chloroformate converts amino acids, amines and related polar compounds into volatile derivatives suitable for gas chromatography. The quantities are small and the specification demanding, because an impurity invisible in a production vessel will show up as a peak in a chromatogram.
Need ethyl chloroformate to a low-phosgene specification?
Tell us the assay, residual phosgene and acidity 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 6.1 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 — gas chromatography quantifying diethyl carbonate and ethanol alongside the main component.
- Residual phosgene — tested specifically, because its significance is a safety question rather than a yield one.
- Free acidity — titration. It predicts how the material will behave over the next few months, not just how it tests today.
- Water content — Karl Fischer titration, since hydrolysis is the principal degradation route.
- Colour and non-volatile residue — handling history and the residue your vessel will see after stripping.
- Boiling range and density — quick identity and purity confirmations.
Common Process Problems & Likely Causes
When ethyl chloroformate 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 |
|---|---|---|
| Coupling yield below the qualification batch | Water in the substrate or solvent hydrolysing the reagent | Karl Fischer on the substrate and solvent; acidity on the reagent |
| Acidity above the certificate | Moisture ingress after the drum was opened, or extended warm storage | Seal discipline, headspace, storage temperature, time since opening |
| Racemisation higher than expected | Mixed anhydride held too long or at too high a temperature before the amine is added | Addition temperature, hold time and base choice against your qualification run |
| Carbonate by-product in the product stream | Diethyl carbonate in the reagent, or over-reaction with an alcohol co-solvent | Diethyl carbonate figure on the COA; solvent system |
| Vigorous gassing on opening a drum | Hydrolysis inside the container generating HCl and carbon dioxide | Vent carefully in a controlled area; check seal and liner before use |
| Material degrading faster than expected in store | Elevated free acidity catalysing further breakdown | Acidity on receipt; store cool and use older stock first |
| Vapour accumulating at floor level | Heavier-than-air flammable vapour collecting in pits and low areas | Ventilation design, ignition source control, low-level extraction |
Packaging, Storage & Shipping
- Standard packing. 200 kg net in lined MS drums, with ISO tank containers arranged where volumes and routings permit.
- Flammability. The flash point near 16 °C means the vapour is flammable at ordinary ambient temperature. Earth and bond during transfer, control ignition sources and use flameproof equipment.
- Vapour behaviour. The vapour is heavier than air and collects in pits, sumps and low-lying areas. Design ventilation for that, not just for general room air changes.
- Moisture exclusion. Hydrolysis is the main degradation route and the source of the acidity that accelerates further breakdown. Keep drums sealed and transfer lines dry and nitrogen-purged.
- Storage. Cool, dry, well-ventilated and bunded, out of direct sun, away from water, alcohols, amines, bases and oxidising agents. Cool storage materially extends usable life.
- Materials of construction. Dry mild steel, glass-lined equipment or suitable fluoropolymer-lined systems with PTFE seals. Avoid rubber and most elastomers.
- Shelf life. Typically 12 months in unopened original packing under those conditions, shorter if stored warm. Re-test assay and acidity rather than assume.
- Transport classification. Shipped under UN 1182, Ethyl chloroformate, Class 6.1 with subsidiary risks 3 and 8, Packing Group I. Confirm against the current SDS and the shipper's declaration for your destination and mode.
Hazards & Safe Handling
Ethyl chloroformate is fatal or toxic if inhaled, causes severe skin burns and eye damage, is strongly lachrymatory and is a flammable liquid. It is among the more hazardous products in this range and must be handled in a closed system by trained personnel under a proper risk assessment — the current SDS supplied with your consignment is the governing document.
- Inhalation is the critical hazard. Acute inhalation toxicity is what puts this product in Packing Group I. Handle in a closed system under local exhaust ventilation with vent scrubbing, never in open vessels.
- Flammability. With a flash point near 16 °C the vapour is flammable at ordinary room temperature. Earth and bond transfer equipment, eliminate ignition sources and use flameproof electrical equipment in the handling area.
- Heavier-than-air vapour. Vapour accumulates at low level and can travel to a distant ignition source. Low-level ventilation and attention to pits and sumps matter more here than general room ventilation.
- Skin and eye contact. Causes severe burns. Chemical-resistant gloves rated for chloroformates, chemical goggles with a face shield, and chemical-resistant clothing.
- Residual phosgene. Commercial material contains trace phosgene, and decomposition can generate more. This is a further reason the product belongs in a closed, extracted system rather than an open one.
- Incompatibilities. Water, alcohols, amines, strong bases, oxidising agents and dimethyl sulphoxide.
- Spill response. Evacuate and ventilate, eliminate ignition sources, then contain and absorb with dry inert non-combustible material and collect in a dry labelled container. Do not use water.
- First aid. Move to fresh air and get immediate medical attention after any inhalation exposure, even if symptoms seem mild, because respiratory effects can be delayed. Remove contaminated clothing, wash skin with plenty of water and flush eyes for at least 15 minutes, with the SDS to hand.
Regulatory & Compliance Notes
Ethyl chloroformate is an established industrial chemical, a Packing Group I dangerous good, and a phosgene derivative subject to additional scrutiny in several territories. 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.
- Dangerous goods. UN 1182, Class 6.1 with subsidiary risks 3 and 8, Packing Group I. The packing group restricts package sizes, tank options and routings, and raises the documentation burden substantially.
- Phosgene derivative status. As a product made from phosgene and containing trace residual phosgene, it attracts additional regulatory and end-use scrutiny in several jurisdictions.
- Inventory status. Listed on the principal chemical inventories in the major importing regions. Ask us for the inventory confirmation relevant to your destination country.
- Import licensing. Several territories require a specific import licence or permit 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.
- 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 ECF Worldwide
Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Ethyl Chloroformate 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 1182 dangerous-goods declaration with any end-user certificate required issued as a complete set.
- Flexible volumes. A single drum for laboratory qualification, through to tank quantities on a supply contract, subject to the routing restrictions that apply to Packing Group I.
- 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 ECF from Chelora
We are an independent sourcing and supply partner. For ethyl chloroformate that means settling two things at enquiry: the residual phosgene and acidity limits your process requires, and the destination country, because Packing Group I routing and import licensing drive the lead time.
- Documentation on every lot. Batch-specific COA including residual phosgene, diethyl carbonate, acidity and water, current SDS and TDS.
- Samples before commitment. Trial quantities for process qualification ahead of a commercial order, packed cold and dry.
- Quantities. From a single 200 kg drum through to tank quantities on contract supply.
- Regulatory handling. End-user certificates, import licence guidance and Packing Group I routing advice for your destination.
- Export experience. Class 6.1 dangerous-goods documentation, packing and labelling handled for sea and road freight.
- Related reagents. Thionyl chloride, chloroacetyl chloride 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.
Ethyl Chloroformate — Common Questions
The questions our technical desk is asked most often about ECF. If yours isn't here, call or email and you will reach someone who knows the chemistry.
What is the CAS number of Ethyl Chloroformate?
The CAS number for Ethyl Chloroformate is 541-41-3, and its EC number is 208-778-5. It is also listed as ethyl carbonochloridate, ethyl chlorocarbonate and chloroformic acid ethyl ester. The formula is ClCOOC2H5 with a molecular weight of 108.52 g/mol.
What is ethyl chloroformate used for?
Three main jobs. It activates carboxylic acids as mixed carbonic anhydrides for amide and peptide coupling; it converts amines to ethyl carbamates, both as products and as protecting groups; and it reacts with alcohols to give carbonate esters. It is also widely used at laboratory scale to derivatise amino acids and amines for gas chromatography.
Do you supply ethyl chloroformate worldwide?
Yes, subject to the routing restrictions that come with Packing Group I and to any import licensing at destination. We supply across Asia Pacific, Europe, the Middle East, Africa and the Americas as well as throughout India, and handle the full export, dangerous-goods and end-use document set.
Why use a mixed anhydride instead of an acid chloride?
Stereochemistry and cleanliness. The mixed carbonic anhydride is reactive enough to acylate an amine but mild enough to preserve chiral centres that an acid chloride route would put at risk, and when it collapses it releases only carbon dioxide and ethanol — no urea by-product to filter out, as a carbodiimide coupling would leave.
Why does residual phosgene matter?
Because it is a safety specification rather than a yield one. Ethyl chloroformate is made from phosgene and retains traces of it, and decomposition can generate more. Ask for the residual phosgene figure by name — a certificate that omits it is not a complete certificate for this product.
How is ethyl chloroformate manufactured?
By reacting ethanol with phosgene under controlled conditions, with the by-product hydrogen chloride stripped and scrubbed. There is no commercially significant alternative route, which is part of why the product carries the regulatory attention it does. Diethyl carbonate and residual phosgene are the characteristic impurities.
What purity does Chelora supply, and can you meet a tighter specification?
Standard commercial grade is 99.0% minimum assay by GC, with diethyl carbonate held to 0.5%, residual phosgene to 50 ppm, free acidity to 0.1% and water to 0.05% maximum. Pharmaceutical grades with tighter phosgene and acidity limits are available — send us the specification you work to.
Why does my material degrade faster than expected?
Because the degradation is autocatalytic. Hydrolysis produces hydrogen chloride, and that acid catalyses further hydrolysis, so a drum that has picked up moisture or sat warm is on a steeper downward curve than it was on arrival. Store cold, keep it sealed, and use older stock first.
Is it flammable?
Yes, and that is easy to underestimate alongside its toxicity. The flash point is around 16 °C, so the vapour is flammable at ordinary room temperature, and the vapour is heavier than air so it collects in pits and low areas and can travel to a distant ignition source. Earth and bond during transfer and design ventilation for low-level extraction.
How should ethyl chloroformate 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, in an area with ignition sources controlled. Cool storage materially extends usable life. Unopened original packing typically carries a 12-month shelf life, shorter if stored warm.
What are the hazards of handling it?
It is toxic or fatal if inhaled, highly flammable, causes severe skin burns and serious eye damage, and is strongly lachrymatory. Inhalation is the critical route, so it belongs in a closed system under local exhaust ventilation with vent scrubbing and full PPE. Seek medical attention after any inhalation exposure even if symptoms seem mild, because effects can be delayed.
How is it classified for transport?
Under UN 1182, Ethyl chloroformate, Class 6.1 toxic with subsidiary risks 3 flammable and 8 corrosive, Packing Group I. We prepare the packing, marking, labelling and declarations for sea and road freight. Confirm the classification against the current SDS for your destination and mode.
How does it compare with methyl, isobutyl and benzyl chloroformate?
The alkyl group is the variable. Methyl chloroformate is smaller and more volatile; isobutyl chloroformate is bulkier and often preferred for mixed anhydride peptide coupling; benzyl chloroformate installs the removable Cbz protecting group. Ethyl sits in the middle and is the economical general-purpose choice.
What packing sizes and order quantities are available?
Standard packing is 200 kg net in lined MS drums, with ISO tank containers arranged where volumes and routings permit. Orders run from a single drum for trial work up to tank quantities on contract supply, within the constraints that Packing Group I imposes.
Ready to source Ethyl Chloroformate?
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.