page_title: 3,4-Ethylenedioxythiophene
section_title: Synthesis and polymerization
hierarchical_section_title: 3,4-Ethylenedioxythiophene / Synthesis and polymerization
caption_attribution_description: English: scheme for synthesis of ethylenedioxythiophene
context_page_description: 3,4-Ethylenedioxythiophene is the organosulfur compound with the formula C₂H₄O₂C₄H₂S. The molecule consists of thiophene, substituted at the 3 and 4 positions with an ethylene glycolyl unit. It is a colorless viscous liquid.
  EDOT is the precursor to the polymer PEDOT, which is found in electrochromic displays, photovoltaics, electroluminescent displays, printed wiring, and sensors.
context_section_description: The original synthesis proceeded via the diester of 3,4-dihydroxythiophene-2,5-dicarboxylate.
  EDOT is often prepared from C4 precursors such as butanediol and butadiene via routes that produce the thiophene and dioxane rings in separate steps.  Representative is the reaction of 2,3-butanedione, trimethylorthoformate, and ethylene glycol to form the dioxane.  Sulfidization with elemental sulfur gives the bicyclic target.
  EDOT is converted into the conducting polymer PEDOT by oxidation.  The mechanism for this conversion begins with production of the radical cation [EDOT]⁺, which attacks a neutral EDOT molecule followed by deprotonation.  Further similar steps result in the dehydropolymerization.  The idealized conversion using peroxydisulfate is shown
  n C₂H₄O₂C₄H₂S + n (OSO₃)₂²⁻   →  [C₂H₄O₂C₄S]ₙ  +  2n HOSO₃⁻
  For commercial purposes, the polymerization is conducted in the presence of polystyrenesulfonate.
caption: One synthesis of EDOT.
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