Ethyl Mercaptan (CAS No. 75-08-1)

Ethyl mercaptan, also known as ethanethiol. With the chemical formula C₂H₆S, it is a clear, colorless low-boiling liquid exhibiting an overpowering garlic-like or skunk-like odor detectable at very low concentrations. 

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

Key Properties

Ethyl mercaptan demonstrates well-defined physical and chemical attributes that align with its odorant and synthetic roles. The table below summarizes essential specifications:

Property Value/Description
Appearance Clear, colorless liquid
Purity ≥99.0% (GC)
Density (20°C) 0.826 g/cm³
Boiling Point 35-36°C
Melting Point -148°C
Flash Point -48°C (closed cup)
Refractive Index (20°C) 1.425
Solubility in Water 0.7% at 20°C (slightly soluble)
Vapor Pressure (20°C) 442 mmHg

Applications and Uses

Ethyl mercaptan’s potent odor and chemical reactivity enable its targeted deployment across energy, agriculture, and food sectors:

  • Gas Odorants: Added at 1-10 ppm to odorless natural gas, propane, and LPG. This imparts a warning scent for leak detection, boosting safety in homes and industry.
  • Chemical Intermediates: Serves as a building block in the synthesis of methionine (an essential amino acid), pesticides, and pharmaceuticals through thiol-disulfide exchange and alkylation reactions.
  • Flavor and Fragrance: Utilized in trace amounts to impart savory, roasted, or garlic notes in food products like cheeses, meats, and beverages, mimicking natural sulfur compounds.
  • Petrochemical Additives: Incorporated in fuel formulations for odor masking and as a scavenger for mercaptans in refining processes to prevent corrosion.
  • Research Applications: Employed in biochemical studies of thiol metabolism and as a reagent in organic synthesis for introducing sulfur functionalities.

Its biodegradability under aerobic conditions supports environmentally conscious use in odorization and synthesis.

Safety and Handling

Ethyl mercaptan is highly flammable, toxic, and irritating, with vapors heavier than air that can travel to ignition sources. It causes severe skin/eye irritation, respiratory distress, and central nervous system effects upon exposure. it is very toxic to aquatic life. Primary guidelines include:

  • Storage: Store in a cool, dry, well-ventilated area below 15°C in grounded. stainless steel or aluminum containers with inhibitors to prevent polymerization. Keep away from oxidizers and heat.
  • Handling: Use PPE including chemical-resistant gloves, goggles, full-face respirators with organic vapor cartridges.And flame-retardant clothing. Work in explosion-proof fume hoods; avoid inhalation due to low odor threshold (0.001 ppm).
  • Environmental Impact: Persistent in groundwater; implement spill containment with inert absorbents and neutralize with bleach solutions before disposal to mitigate ecological harm.
  • Regulatory Compliance: UN 2363 (Class 3, PG I); complies with GHS (H225: Extremely flammable; H301+H331: Toxic if swallowed/inhaled; H314: Causes severe burns; H400: Very toxic to aquatic life) and REACH/TSCA for thiols.

Consult the Safety Data Sheet (SDS) for detailed exposure limits (PEL 0.5 ppm) and emergency procedures.

Frequently Asked Questions (FAQs)

What is the primary use of Ethyl mercaptan?

It is mainly used as an odorant additive for natural gas and LPG, providing a skunk-like smell at trace levels to alert users to dangerous leaks.

Is Ethyl mercaptan safe for industrial applications?

It is highly flammable and toxic, requiring strict ventilation, PPE, and ignition controls, but is safely managed in odorization facilities with automated dosing systems.

What is the shelf life of Ethyl mercaptan?

Stored stabilized below 15°C in sealed containers, it remains stable for 1-2 years; monitor for discoloration or odor changes indicating oxidation.

Can Ethyl mercaptan be shipped internationally?

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

How does Ethyl mercaptan compare to methyl mercaptan as an odorant?

It offers a milder, less pungent odor than methyl mercaptan, making it preferable for residential gas applications while providing similar detection sensitivity.

Is Ethyl mercaptan soluble in water?

It has low water solubility (0.7%), but is highly miscible with alcohols and hydrocarbons, facilitating easy blending into fuels without phase separation.

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