3,4-Ethylenedioxythiophene

3,4-Ethylenedioxythiophene

Names
Preferred IUPAC name 2,3-Dihydrothieno[3,4-b][1,4]dioxine
Identifiers
CAS Number	126213-50-1
3D model (JSmol)	Interactive image
Beilstein Reference	7126466
ChemSpider	3622202
ECHA InfoCard	100.122.178
EC Number	603-128-0
PubChem CID	4421864
UNII	8SEC7Q2K7G Y
CompTox Dashboard (EPA)	DTXSID301047399 DTXSID40888925, DTXSID301047399
InChI InChI=1S/C6H6O2S/c1-2-8-6-4-9-3-5(6)7-1/h3-4H,1-2H2 Key: GKWLILHTTGWKLQ-UHFFFAOYSA-N
SMILES C1COC2=CSC=C2O1
Properties
Chemical formula	C6H6O2S
Molar mass	142.17 g·mol−1
Appearance	colorless liquid
Density	1.34 g/cm3[1]
Melting point	10.5 °C (50.9 °F; 283.6 K)[1]
Boiling point	225 °C (437 °F; 498 K)[1]
Solubility in water	2.1 g/L[1]
Viscosity	11 mPa·s[1]
Hazards
GHS labelling:[2]
Pictograms
Signal word	Danger
Hazard statements	H302, H311, H312, H319, H412
Precautionary statements	P262, P264, P264+P265, P270, P273, P280, P301+P317, P302+P352, P305+P351+P338, P316, P317, P321, P330, P337+P317, P361+P364, P362+P364, P405, P501
Flash point	104 °C (219 °F; 377 K)[1]
Autoignition temperature	360 °C (680 °F; 633 K)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

3,4-Ethylenedioxythiophene (EDOT) is an 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.^[3]

EDOT is the precursor to the polymer PEDOT, which is found in electrochromic displays, photovoltaics, electroluminescent displays, printed wiring, and sensors.^[4][5]

Synthesis and polymerization

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, trimethyl orthoformate, and ethylene glycol to form the dioxane. Sulfidization with elemental sulfur gives the bicyclic target.^[6]

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.^[5]

References