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Ethyl P-Toluenesulfonate (CAS 80-40-0): A Complete Technical & Industry Guide
Ethyl p-toluenesulfonate — known industrially as EtOTs — is one of the most versatile sulfonate ester intermediates in modern organic chemistry. From pharmaceutical synthesis to specialty polymer production, its role as a powerful yet controllable alkylating agent makes it indispensable across multiple sectors. This guide examines its chemical identity, physical and reactivity profile, manufacturing considerations, regulatory requirements, and key sourcing factors.
1. Chemical Identity & Molecular Profile
Ethyl p-toluenesulfonate (EtOTs) is the ethyl ester of para-toluenesulfonic acid. It belongs to the sulfonate ester family — compounds renowned for their superior leaving-group ability relative to simple halides. The compound is registered under CAS Number 80-40-0 and carries the IUPAC name ethyl 4-methylbenzenesulfonate.
Quick Reference — Chemical Identity
The structure consists of a para-methylphenyl (tosyl) group attached via a sulfonate bridge to an ethyl chain. The sulfonyl oxygen atoms draw electron density toward sulfur, creating a strongly electrophilic carbon at the ethyl terminus — the origin of EtOTs's alkylating power.
2. Physical & Chemical Properties
At ambient conditions, EtOTs is typically encountered as a colorless to light yellow liquid. The compound solidifies near its melting point, meaning temperature management during storage and processing is important. The table below summarizes the key physical parameters as specified in Jinli Chemical's product documentation:
| Parameter | Unit | Specification | Significance |
|---|---|---|---|
| Appearance | — | Colorless to light yellow liquid | Visual quality indicator |
| Purity (min) | % w/w | ≥ 98 | Reaction selectivity & yield |
| Melting Point (min) | °C | ≥ 32 | Storage temperature guideline |
| Water Content (max) | % w/w | ≤ 0.30 | Hydrolysis prevention |
| PTSA (max) | % w/w | ≤ 0.20 | By-product control |
| PTSC (max) | % w/w | ≤ 0.20 | By-product control |
| Ash (max) | % w/w | ≤ 0.05 | Inorganic impurity control |
| Molecular Weight | g/mol | 200.25 | Stoichiometric calculations |
Reactivity Characteristics
EtOTs is a selective electrophile. Its leaving group — the tosylate anion (TsO⁻) — is among the weakest bases in organic chemistry, which translates into one of the highest leaving group abilities achievable without highly activated substrates. This property enables clean SN2 displacement at the ethyl carbon under mild conditions and reduces competing E2 elimination pathways relative to primary alkyl halides.
The compound also undergoes hydrolysis in the presence of water, regenerating ethanol and p-toluenesulfonic acid. This sensitivity underpins the strict ≤ 0.30% water limit in the specification and informs storage requirements.
3. Synthesis Routes & Manufacturing
The standard industrial route involves esterification of p-toluenesulfonic acid (or its sodium salt) with ethanol under acid catalysis, or — more reliably for high purity — reaction of p-toluenesulfonyl chloride (PTSC) with ethanol in the presence of a base (such as pyridine or triethylamine) that scavenges the liberated hydrogen chloride:
Jinli Chemical manufactures both P-Toluene Sulfonyl Chloride (PTSC) and EtOTs in-house, giving the company control over upstream raw material quality — a critical advantage for batch-to-batch consistency.
| Method | Reagents | Typical Yield | Key Advantage | Key Limitation |
|---|---|---|---|---|
| Acid-catalyzed esterification | PTSA + EtOH + H⁺ catalyst | Moderate (70–80%) | Low-cost reagents | Equilibrium-limited; higher PTSA residuals |
| Acid chloride + alcohol | PTSC + EtOH + base | High (85–95%) | High purity; fast reaction | Requires base neutralisation step |
| Sodium tosylate + alkyl halide | NaOTs + EtBr | Moderate–high | Avoids HCl generation | Alkyl halide handling & disposal |
4. Industrial Applications
EtOTs is a multi-sector intermediate. Its primary value lies in transferring an ethyl group to a nucleophile — a transformation needed across pharmaceuticals, agrochemicals, dyes, and specialty materials.
| Sector | Role of EtOTs | Example Targets |
|---|---|---|
| Pharmaceutical Synthesis | O-alkylation, N-alkylation, S-alkylation of APIs and intermediates | Ethyl ethers of phenolic drugs; N-ethyl amino-compounds |
| Agrochemicals | Synthesis of herbicide & fungicide intermediates | Ethylated triazines; ethyl sulfonyl herbicide precursors |
| Dyes & Pigments | N-ethylation of amine-containing chromophores | Cationic dye intermediates |
| Polymer Additives | Chain-end modification; initiator synthesis | Ethyl-capped oligomers; controlled radical polymerisation |
| Fragrance & Flavor | Selective etherification of aroma compounds | Aromatic ethyl ethers with characteristic scent profiles |
| Academic / Research | Mechanistic studies; reaction method development | Model SN2 substrate; isotope labelling |
Pharmaceutical & Fine Chemical Synthesis
In pharmaceutical manufacturing, EtOTs excels where ethyl iodide or diethyl sulfate would require more aggressive conditions or leave more hazardous residuals. Regulatory agencies increasingly scrutinise mutagenic impurities (the ICH M7 guideline), and switching from dialkyl sulfates to sulfonate esters of defined purity is one strategy chemists use to maintain acceptable thresholds while retaining reactivity.
Comparison: EtOTs vs. Common Ethylating Agents
| Reagent | Leaving Group Ability | Selectivity | Safety Profile | Preferred Use Case |
|---|---|---|---|---|
| EtOTs (this product) | Excellent | High SN2 | Moderate; irritant/alkylating | Fine chemical, pharma |
| Ethyl iodide (EtI) | Very high | High | Volatile; lachrymatory | Lab scale |
| Diethyl sulfate (Et₂SO₄) | High | Moderate | Carcinogen (IARC Group 2A) | Bulk industrial |
| Ethyl bromide (EtBr) | Good | High | Volatile; narcotic | Lab scale |
| Triethyl oxonium tetrafluoroborate | Excellent | Very high | Moisture-sensitive; costly | Speciality/research |
5. Handling, Storage & Safety
Hazard Summary
As a sulfonate ester, EtOTs can react with DNA and biological macromolecules through the same mechanism that makes it useful synthetically. Prolonged or repeated skin contact and inhalation of vapour should be avoided. Appropriate personal protective equipment — including chemical-resistant gloves, safety goggles, and in enclosed spaces a suitable respirator — is required.
| Parameter | Requirement | Rationale |
|---|---|---|
| Temperature | Store below 30 °C (cool, dry location) | Prevent liquefaction / thermal decomposition |
| Moisture | Seal containers tightly; use desiccant where possible | Hydrolysis yields p-toluenesulfonic acid |
| Light | Protect from direct sunlight | Photo-oxidation can cause yellowing & impurity formation |
| Incompatibilities | Strong bases, oxidisers, water | Violent or exothermic reactions possible |
| Ventilation | Handle in fume cupboard or well-ventilated area | Reduce vapour inhalation risk |
| Container | HDPE or glass; avoid reactive metals | Prevent contamination via sulfonate corrosion |
6. Regulatory & Quality Considerations
Globally, sulfonate esters fall within the scope of ICH M7 ("Assessment and Control of DNA Reactive (Mutagenic) Impurities in Pharmaceuticals"), which requires pharmaceutical manufacturers to evaluate EtOTs either as a potential impurity in drug substances or as an intermediate warranting control. Companies sourcing EtOTs for GMP processes should request CoA (Certificate of Analysis) documentation and ideally a qualified impurity profile.
Jinli Chemical operates from the Jiaxing Port Area Chemical Park, a regulated industrial zone in Zhejiang Province, China — a region with significant chemical manufacturing infrastructure and compliance oversight. The company offers documentation support for customers requiring quality traceability.
7. About Jiaxing Jinli Chemical Co., Ltd.
Jiaxing Jinli Chemical Co., Ltd. is a manufacturer and supplier of sulfonates, intermediates, plasticizers, blowing agents, and disinfectants based at the Intersection of Pinghai Road and Binhai Avenue, Jiaxing Port Area Chemical Park, China. The company supplies both domestic and international markets, offering a technically grounded product portfolio centred on toluenesulfonate chemistry.
Ethyl p-toluenesulfonate is positioned within Jinli's Intermediates Series — a product line that includes closely related compounds such as:
Beyond intermediates, Jinli Chemical's portfolio spans plasticiser series products (including sulfonamide-based plasticisers for nylon and engineering thermoplastics) and forming & blowing agents widely used in foam rubber, EVA, and thermoplastic elastomers.
The company's R&D and technology direction can be explored via their Technology page, while procurement and sample enquiries can be directed through the Contact page.
8. Market Outlook
Demand for high-purity sulfonate esters like EtOTs continues to grow alongside expansion in generic pharmaceutical manufacturing, particularly in India and China, and the rising need for mutagenic-impurity-compliant synthetic pathways in regulated markets. As diethyl sulfate faces intensified regulatory scrutiny (IARC Group 2A classification), formulators in pharmaceutical, agrochemical, and specialty chemical sectors are increasingly evaluating EtOTs and related sulfonate esters as safer, structurally equivalent alternatives.
Supply concentration in established chemical parks — such as Jiaxing, Zhejiang — offers manufacturers co-location advantages, including shared infrastructure and access to upstream toluenesulfonic acid and sulfonyl chloride streams, supporting competitive pricing and supply reliability.