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1. What Is Ethyl P-Toluenesulfonate
Ethyl p-toluenesulfonate (also called ethyl tosylate or p-toluenesulfonic acid ethyl ester) is the ethyl ester of p-toluenesulfonic acid. It belongs to the sulfonate ester family and is widely used as an ethylating (alkylating) reagent in organic synthesis, taking advantage of the tosylate group's strong leaving-group character in nucleophilic substitution reactions.
| Product Name | Ethyl p-Toluenesulfonate |
|---|---|
| Synonyms | Ethyl tosylate; p-Toluenesulfonic acid ethyl ester; Ethyl 4-methylbenzenesulfonate |
| CAS Number | 80-40-0 |
| Molecular Formula | C9H12O3S |
| Molecular Weight | 200.25 g/mol |
| EC Number | 201-276-7 |
2. Physical & Chemical Properties
At room temperature ethyl p-toluenesulfonate typically appears as a colorless to pale yellow liquid or low-melting solid, depending on ambient temperature and purity. Reported literature values are summarized below; batch-specific figures should always be confirmed on the Certificate of Analysis (COA).
| Property | Typical Value |
|---|---|
| Appearance | Colorless to light yellow liquid / low-melting solid |
| Melting Point | Approx. 29–33 °C (lit.) |
| Boiling Point | Approx. 158–162 °C at 10 mmHg (lit.) |
| Density | Approx. 1.17 g/mL at 25 °C |
| Refractive Index | n20/D ≈ 1.511 |
| Solubility | Soluble in ethanol, ether and most organic solvents; limited solubility in water |
| Flash Point | Approx. 157 °C |
3. Production Method
Ethyl p-toluenesulfonate is generally produced by the esterification of p-toluenesulfonic acid (PTSA) or p-toluenesulfonyl chloride (PTSC) with ethanol, followed by neutralization, phase separation, washing and vacuum distillation or crystallization to remove residual acid, water and salts. Reaction temperature, ethanol excess and catalyst control directly affect the finished purity and residual PTSA/PTSC content, which is why these parameters are tracked as key in-process quality checkpoints.
4. Applications
As an efficient ethylating agent, ethyl p-toluenesulfonate is used across fine chemical, agrochemical and pharmaceutical intermediate synthesis. The table below compares it with its closest analog, methyl p-toluenesulfonate, to help formulators choose the correct alkylating reagent.
| Use Case | Ethyl p-Toluenesulfonate | Methyl p-Toluenesulfonate |
|---|---|---|
| Alkyl group transferred | Ethyl (–C₂H₅) | Methyl (–CH₃) |
| Typical role | Ethylating reagent, intermediate for sensitizing materials | Methylating reagent |
| Common industry use | Organic synthesis; cellulose acetate flexibilizer | Organic synthesis intermediate |
Ethyl p-toluenesulfonate also has documented use as an analytical reference standard: it has been used to develop headspace and solid-phase microextraction GC/MS methods for monitoring residual alkyl sulfonate genotoxic impurities in active pharmaceutical ingredients (see references below).
5. Quality Specifications
A representative commercial specification for industrial-grade material is shown below. Contact [Your Company Name] for the current Certificate of Analysis and lot-specific data.
| Check Point | Unit | Specification |
|---|---|---|
| Appearance | – | Colorless to light yellow liquid |
| Purity | % min | 98 |
| Melting Point | °C min | 32 |
| Water Content | % max | 0.3 |
| Residual PTSA | % max | 0.2 |
| Residual PTSC | % max | 0.2 |
| Ash | % max | 0.05 |
6. Safety, Handling & Storage
Ethyl p-toluenesulfonate is classified as an irritant to skin and eyes and should be handled with chemical-resistant gloves, goggles and adequate ventilation or local exhaust. Because alkyl sulfonate esters of this type can act as alkylating agents, some regulatory and pharmacopoeial guidance treats residues of this class as potential genotoxic impurities in drug substances, so downstream users in pharmaceutical manufacturing should verify control limits appropriate to their process.
- Store in a cool, dry, well-ventilated area away from strong oxidizers and heat sources.
- Keep containers tightly sealed to minimize moisture uptake, which can affect purity and melting point.
- Use appropriate personal protective equipment (gloves, goggles, lab coat) during handling and sampling.
- Consult the current Safety Data Sheet (SDS) before use, transport or disposal.
7. Frequently Asked Questions
Is ethyl p-toluenesulfonate the same as ethyl tosylate?
Yes, "ethyl tosylate" is a common shorthand name for ethyl p-toluenesulfonate (CAS 80-40-0).
What is the difference between ethyl and methyl p-toluenesulfonate?
They differ only in the alkyl group transferred during a reaction — ethyl versus methyl — which affects which
alkylated product is formed and the reagent's reactivity and volatility.
What packaging is available for bulk orders?
[Your Company Name] can advise on drum, IBC or customized packaging based on order volume and shipping
destination — see the contact section below.