Synthesis & Preparation
Industrial and laboratory routes · CAS 540-63-6
C₂H₆S₂ · MW 94.19 g/mol
Abstract
This review summarises the principal routes to 1,2-ethanedithiol, from the high-volume industrial reaction of 1,2-dichloroethane with sodium hydrosulfide to the classical laboratory thiourea method. Catalytic and phase-transfer variants, oligomerisation behaviour and derivatisation chemistry are also considered.
Industrial Synthesis
The industrial route reacts 1,2-dichloroethane with sodium hydrosulfide in aqueous or alcoholic solution. Hydrosulfide is a strong nucleophile, so substitution takes place at both carbon centres, and the dithiol is isolated by distillation (boiling point 144–146 °C) after the sodium chloride by-product has been removed (Housecroft & Sharpe, 2018; NIST, 2024).
Yields are governed by the excess of hydrosulfide used, the reaction temperature and the efficiency of product separation. Excess reagent drives the second substitution to completion, while side reactions lower the isolated yield: the intermediate 2-chloroethanethiol can cyclise to thiirane, and partly substituted material can combine into oligomeric sulfides.
ClCH₂CH₂Cl + 2 NaSH → HSCH₂CH₂SH + 2 NaCl
Laboratory Synthesis (Thiourea Method)
2.1Reaction sequence and isolation
The classical laboratory procedure treats 1,2-dibromoethane with thiourea to form the bis(isothiouronium) salt. Aqueous base hydrolyses the isothiouronium groups to urea, releasing the dithiolate, which is then acidified to give the free dithiol.
The method is valued for its reproducibility at laboratory scale: the intermediate salt is a stable solid that can be isolated and stored before use, and the final acidification is monitored so that the product is not held under strongly acidic conditions longer than necessary.
BrCH₂CH₂Br + 2 (H₂N)₂C=S → (H₂N)₂C⁺–S–CH₂CH₂–S–C⁺(NH₂)₂ · 2 Br⁻
+ 4 NaOH → NaS–CH₂CH₂–SNa + 2 (H₂N)₂C=O + 2 H₂O + 2 NaBr
+ 2 H₃O⁺ → HSCH₂CH₂SH + 2 H₂O + 2 Na⁺
Alternative & Catalytic Routes
Later work describes catalytic and phase-transfer-assisted variants that shorten reaction time and improve selectivity toward the linear dithiol. In one tri-phase protocol, 1,2-dibromoethane was treated with aqueous sodium hydrosulfide (molar ratio 1 : 2.2) over a polymer-supported quaternary ammonium catalyst in toluene at 75 °C for 5.5 h, giving the dithiol in 50–55% yield at high conversion of the dibromide (Xing et al., 2010).
Routes through ethylene oxide or ethylene sulfide derivatives, and through thioacetate intermediates that are hydrolysed in a final step, are also used where a milder sulfur source is required.
Oligomerization & Derivatization
Under oxidising conditions EDT is converted into oligomeric and polymeric disulfides, and in strongly alkaline media the thiolate oxidises more readily still. Inert-atmosphere handling and reducing agents suppress these pathways, while deliberate oxidation is used to build sulfur-rich chains and cyclic derivatives.
Related reference pages: Molecule Profile|Safety & Regulatory|Product & Inquiry
References
- Housecroft, C. E., & Sharpe, A. G. (2018). Inorganic chemistry (5th ed.). Pearson.
- NIST. (2024). 1,2-Ethanedithiol. NIST Chemistry WebBook, SRD 69. https://webbook.nist.gov
- Xing, J., Zhang, Y., & Wang, Z. (2010). Synthesis of 1,2-ethanedithiol with tri-phase phase transfer catalysis method. Chemical Industry and Engineering Progress, 29(1).