Ethanethiol

Description

Ethane thiol, commonly known as ethyl mercaptan, is a colorless gas or clear liquid with a distinct odor. It is an organosulfur compound with the formula CH₃CH₂SH. Abbreviated EtSH, it consists of an ethyl group (Et), CH₃CH₂, attached to a thiol group, SH. Its structure parallels that of ethanol, but with S instead of O. The odor of EtSH is infamous. Ethanethiol is more volatile than ethanol due to a diminished ability to engage in hydrogen bonding. Ethanethiol is toxic. It occurs naturally as a minor component of petroleum, and may be added to other wise odorless gaseous products such as liquefied petroleum gas (LPG) to help warn of gas leaks. At these concentrations, ethanethiol is not harmful.

Description

Ethanethiol, or ethyl mercaptan, is best known as the smell of a natural gas leak. It has been added to natural gas supplied to many areas because it can be identified by humans at the extremely low concentration of ~8.7 ppt. It is also used to treat petroleum processing catalysts, and as a precursor for herbicides and pesticides.

Chemical properties

A yellowish liquid (or a colorless gas above the BP). fruity, sulfur aroma. Strong, sharp odor of garlic or skunklike odor.

Physical properties

Colorless liquid with a strong, disagreeable, skunk-like or rotten egg odor. Extremely flammable liquid or gas. An experimentally determined odor threshold concentration of 1 ppb_v was reported by Leonardos et al. (1969). Katz and Talbert (1930) reported experimental detection odor threshold concentrations in the range 0.66–7.6 μg/m³ (0.26 to 3.0 ppb_v).

The Uses of Ethanethiol

Ethanethiol is used as an intermediate inthe manufacture of insecticides, plastics, andantioxidants; and as an additive to natural gasto give odor. It occurs in illuminating gas andin petroleum distillates.

The Uses of Ethanethiol

LPG odorant, adhesive, stabilizer, chemical intermediate.

The Uses of Ethanethiol

Stenching agent for liquefied petroleum gases; adhesive stabilizer; manufacture of plastics, insecticides, and antioxidants

Preparation

Ethanethiol is prepared by the reaction of ethylene with hydrogen sulfide over a catalyst. The various producers utilize different catalysts in this process. It is also be prepared commercially by the reaction of ethanol with hydrogen sulfide gas over an acidic solid catalyst, such as alumina.
Ethanethiol was originally reported by Zeiss in 1834 . Zeise treated calcium ethyl sulfate with a suspension of barium sulfide saturated with hydrogen sulfide. He is credited with naming the C₂H₅S- group as mercaptum.
Ethanethiol can also be prepared by a halide displacement reaction, where ethyl halide is reacted with aqueous sodium bisulfide. This conversion was demonstrated as early as 1840 by Henri Victor Regnault.

Production Methods

Ethyl mercaptan is prepared by distilling ethyl potassium sulfate with potassium hydrogen sulfide. Additional mercaptans can be prepared in a similar manner with the corresponding proper ingredients.

Definition

ChEBI: Ethanethiol is an alkanethiol that is ethane substituted by a thiol group at position 1. It is added to odorless gaseous products such as liquefied petroleum gas (LPG) to provide a garlic scent which helps warn of gas leaks. It has a role as a rodenticide.

What are the applications of Application

Ethanethiol can be used as a reactant for the synthesis of:
Functionalized oxazolidinones by conjugated nucleophilic addition- electrophilic amination reaction.
Ethyl phenyl sulfide by C-S coupling with iodobenzene.
Chain transfer agent in the RAFT polymerization of N-isopropylacrylamide.

Reactions

Ethane thiol is a valued reagent in organic synthesis. In the presence of sodium hydroxide, it gives the powerful nucleophile SEt-. The salt can be generated quantitatively by reaction with sodium hydride.
Ethane thiol can be oxidized to ethyl sulfonic acid, using bleach and related strong aqueous oxidants. Weaker oxidants, such as ferric oxide give the disulfide, diethyl disulfide :
2 EtSH + H₂O₂ → EtS-SEt + 2 H₂O
Like other thiols, it behaves comparably to hydrogen sulfide. For example, it binds, concomitant with deprotonation to "soft" transition metal cations, such as Hg²⁺, Cu⁺, and Ni²⁺ to give polymeric thiolato complexes, Hg(SEt)₂, CuSEt, and Ni(SEt)₂, respectively.

Aroma threshold values

High strength odor, sulfurous fruity type; recommend smelling in a 0.01% solution or less.

General Description

A clear colorless low-boiling liquid (boiling point 97°F) with an overpowering, garlic-like/skunk-like odor. Flash point -55°F. Less dense than water and very slightly soluble in water. Vapors are heavier than air. Vapors may irritate nose and throat. May be toxic if swallowed, by inhalation or by contact. Added to natural gas as an odorant. Used as a stabilizer for adhesives.

Air & Water Reactions

Highly flammable. A very dangerous fire hazard. Very slightly soluble in water.

Reactivity Profile

Ethanethiol reacts violently with calcium hypochlorite, May react vigorously with other oxidizing reagents. On contact with strong acids or when heated to decomposition Ethanethiol emits highly toxic fumes of sulfur oxides [Sax, 9th ed., 1996, p. 1575].

Hazard

Toxic by ingestion and inhalation. Flammable, dangerous fire risk.

Health Hazard

Inhalation of vapor causes muscular weakness, convulsions, respiratory paralysis. High concentrations may cause pulmonary irritation. Liquid irritates eyes and skin. Ingestion causes nausea and irritation of mouth and stomach.

Health Hazard

The inhalation toxicity of ethanethiol islower than that of methanethiol. Intraperitoneal administration in rats at sublethaldoses caused deep sedation, followed bylethargy, restlessness, lack of muscular coordination, and skeletal muscle paralysis.Higher doses produced cyanosis, kidney andliver damage, respiratory depression, coma,and death. The intraperitoneal LD50 value inrats was 450 mg/kg (ACGIH 1986).
Ethanethiol is metabolized to inorganicsulfate and ethyl methyl sulfone, and excreted. The oral LD50 value in rats is 680 mg/kg.
In humans, repeated exposures to itsvapors at about 5 ppm concentration canproduce irritation of the nose and throat,headache, fatigue, and nausea.

Chemical Reactivity

Reactivity with Water No reaction; Reactivity with Common Materials: No reaction; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Not pertinent; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent.

Safety Profile

Moderately toxic by ingestion, inhalation, and intraperitoneal routes. A skin and eye irritant. Inhalation causes central nervous system effects in humans. A very dangerous fire hazard when exposed to heat or flame; can react vigorously with oxidizing materials. A moderate explosion hazard when exposed to spark or flame. Violent reaction with Ca(OCl)2. Will react with water or steam to produce toxic and flammable vapors. To fight fire, use CO2, dry chemical. When heated to decomposition or on contact with acid or acid fumes it emits hghly toxic fumes of SOx. See also MERCAPTANS.

Potential Exposure

This material is used as a warning odorant for liquefied petroleum gases. It is used as an intermediate in the manufacture of many pesticides and other organic chemicals

Environmental Fate

Biological. Ethyl mercaptan did not degrade in anaerobic sediments and sludges nor in anaerobic freshwater conditions (van Leerdam et al., 2006).
Photolytic. A second-order rate constant of 1.21 x 10^-12 cm³/molecule?sec was reported for the reaction of ethyl mercaptan and NO3 radicals in the atmosphere at 297 K (Atkinson, 1991).
Chemical/Physical. In the presence of nitric oxide, ethyl mercaptan reacted with OH radicals forming ethyl thionitrite. The rate constant for this reaction is 2.7 x 10^-11 at 20 °C (MacLeod et al., 1984).

Shipping

UN2363 Ethyl mercaptan, Hazard Class: 3; Labels: 3-Flammable liquid

Purification Methods

Dissolve the thiol in aqueous 20% NaOH, extract it with a small amount of *benzene and then steam distil until clear. After cooling, the alkaline solution is acidified slightly with 15% H2SO4 and the thiol is distilled off, dried with CaSO4, CaCl2 or 4A molecular sieves, and fractionally distilled under nitrogen [Ellis & Reid J Am Chem Soc 54 1674 1932]. It has a foul odour. [Beilstein 1 IV 1390.]

Incompatibilities

May form explosive mixture with air. Slowly forms peroxides. This material is a weak acid. Reacts with oxidizers, causing fire and explosion hazard. Reacts with strong acids evolving toxic and flammable hydrogen sulfide. May accumulate static electrical charges, and may cause ignition of its vapors. Attacks some forms of plastics, coatings and rubber. Aldehydes are frequently involved in self-condensation or polymerization reactions. These reactions are exothermic; they are often catalyzed by acid. Aldehydes are readily oxidized to give carboxylic acids. Flammable and/or toxic gases are generated by the combination of aldehydes with azo, diazo compounds, dithiocarbamates, nitrides, and strong reducing agents. Aldehydes can react with air to give first peroxo acids, and ultimately carboxylic acids. These autoxidation reactions are activated by light, catalyzed by salts of transition metals, and are autocatalytic (catalyzed by the products of the reaction). The addition of stabilizers (antioxidants) to shipments of aldehydes retards autoxidation

Waste Disposal

Incineration (1093℃) followed by scrubbing with a caustic solution