Ethanethiol (CAS No. 75-08-1)

Ethanethiol, also known as ethyl mercaptan. With the chemical formula C₂H₆S, it is a colorless to pale yellow liquid at room temperature, exhibiting high volatility and flammability. This organosulfur reagent serves as a critical intermediate in the synthesis of pharmaceuticals, agrochemicals, and polymers, while also functioning as a gas odorant for natural gas and LPG detection. Its low boiling point and sulfur-donating capability make it indispensable for odorization and derivatization processes requiring precise sensory alerting.

CAS Number: 75-08-1 Molecular Weight: 62.13 g/mol Synonyms: Ethyl mercaptan, Ethanethiol, Mercaptoethane

Key Properties

Ethanethiol provides well-defined physical and chemical characteristics that align with its role in odorization and synthetic applications. The table below summarizes essential specifications:

Property Value/Description
Appearance Colorless to pale yellow liquid
Purity ≥98.0% (GC)
Density (20°C) 0.839 g/cm³
Boiling Point 35-37°C
Melting Point -123.6°C
Flash Point -17°C (closed cup)
Refractive Index (20°C) 1.442
Solubility in Water 0.6 g/100 mL at 20°C (slightly soluble)
Vapor Pressure (20°C) 442 mmHg

These properties underscore its extreme volatility and low ignition energy, necessitating careful handling in ventilated environments.

Applications and Uses

Ethanethiol’s mercapto group enables nucleophilic substitutions and its odor serves as a safety indicator, supporting diverse industrial and research uses:

  • Gas Odorants: Added at trace levels (ppm) to natural gas, propane, and butane for leak detection, providing a garlic-like alert at concentrations below 1% of the lower explosive limit.
  • Organic Synthesis: Acts as a thiolating agent in the preparation of thioethers, sulfides, and mercaptans for pharmaceutical intermediates like ranitidine and in agrochemicals such as insecticides.
  • Polymer Additives: Incorporated as a chain transfer agent in free radical polymerization of styrene and acrylates, controlling molecular weight and enhancing processability.
  • Flavor and Fragrance: Used in trace amounts to impart skunky or garlic notes in food flavorings and perfumery, mimicking natural sulfur compounds.
  • Analytical Chemistry: Serves as a reference standard for gas chromatography and as a reagent in derivatization for trace sulfur analysis.

Its biodegradability under aerobic conditions promotes environmentally responsible use in odorization systems.

Safety and Handling

Ethanethiol is highly flammable, toxic, and malodorous, causing severe irritation to eyes, skin, and respiratory system. Inhalation can lead to pulmonary edema, and it poses asphyxiation risks in confined spaces due to displacement of oxygen. Primary guidelines include:

  • Storage: Store in cool, well-ventilated areas below 15°C in explosion-proof containers made of stainless steel or Teflon; keep away from ignition sources, oxidizers, and alkalis.
  • Handling: Use full PPE including chemical-resistant gloves, goggles, respirators with organic vapor cartridges, and self-contained breathing apparatus. Work in fume hoods; neutralize spills with sodium hypochlorite solution.
  • Environmental Impact: Toxic to aquatic organisms and persistent in groundwater; implement vapor recovery and spill containment to prevent atmospheric or soil release.
  • Regulatory Compliance: UN 2363 (Class 3, PG I); complies with GHS (H225: Highly flammable; H330: Fatal if inhaled; H314: Causes severe burns) and REACH/TSCA for toxic gases.

Consult the Safety Data Sheet (SDS) for odor threshold and exposure limits.

Frequently Asked Questions (FAQs)

What is the primary use of Ethanethiol?

Ethanethiol is mainly used as a warning agent in natural gas and LPG odorization, allowing detection of leaks at safe concentrations before ignition risks arise.

Is Ethanethiol safe for industrial odorization?

It is highly toxic and flammable, requiring specialized handling and ventilation, but effective at low doses (1-10 ppm) for safety without significant health risks in diluted form.

What is the shelf life of Ethanethiol?

Stored in sealed, stabilized containers below 15°C, Ethanethiol remains stable for 12-18 months, though volatility may reduce yield—monitor pressure in storage vessels.

Can Ethanethiol be shipped internationally?

Yes, it is shipped globally under UN 2363 regulations, in pressurized cylinders or drums with safety valves, for quantities from 1 L to bulk tankers.

How does Ethanethiol compare to propanethiol as an odorant?

Ethanethiol has a lower boiling point (35°C vs. 67°C) and more pungent garlic odor than propanethiol’s cabbage scent, making it preferable for low-temperature gas applications.

Is Ethanethiol soluble in water?

It has limited water solubility (0.6 g/100 mL), but is highly miscible with alcohols, ethers, and hydrocarbons, aiding in formulation for gas blending.

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