# 3,4-DIHYDROXY-THIOPHENE-2,5-DICARBOXYLIC ACID DIETHYL ESTER (CAS 1822-66-8)

**CAS:** 1822-66-8  
**PubChem CID:** [245503](https://pubchem.ncbi.nlm.nih.gov/compound/245503)  
**Molecular formula:** C10H12O6S  
**Molar mass:** 260.27 g/mol  
**IUPAC:** diethyl 3,4-dihydroxythiophene-2,5-dicarboxylate  
**SMILES:** `CCOC(=O)C1=C(C(=C(S1)C(=O)OCC)O)O`  
**InChIKey:** `YOKOBAHUBJPMGP-UHFFFAOYSA-N`  
**InChI:** `InChI=1S/C10H12O6S/c1-3-15-9(13)7-5(11)6(12)8(17-7)10(14)16-4-2/h11-12H,3-4H2,1-2H3`  

## Physicochemical properties

| Parameter | Value |
|---|---|
| logP (XLogP3) | 3.1 |
| PSA | 121 Ų |
| Hydrogen bond donors | 2 |
| Hydrogen bond acceptors | 7 |
| Rotatable bonds | 6 |
| Heavy atoms | 17 |

## GHS classification

**Signal word:** Warning

**Pictograms:** GHS07

### Hazard statements (H)

- **H315** — Causes skin irritation
- **H319** — Causes serious eye irritation
- **H335** — May cause respiratory irritation

### Precautionary statements (P)

- **P261** — Avoid breathing dust/fume/gas/mist/vapours/spray

## Available in the shop

[3,4-DIHYDROXY-THIOPHENE-2,5-DICARBOXYLIC ACID DIETHYL ESTER (CAS 1822-66-8) — Beijing Tong Guang](https://molgod.org/sds-cards/34-dihydroxy-thiophene-25-dicarboxylic-acid-diethyl-ester-cas-1822-66-8-beijing-tong-guang/)

## Regulatory compliance checklist

Status based on: ADR 2025 (Table A), REACH Annex XVII, CLP Annex VI (harmonised classification), hazard class from the m14-spill DB, SVHC, GIS and the Polish OEL list. Principle: no data = no claim (we do NOT declare "no restrictions" without a basis).

4 required / 12 items

### SDS (Safety Data Sheet) available

- **required** (required / sds)
- How to comply: Requirement: current SDS compliant with Reg. 1907/2006 (REACH) Annex II, 16-section format.
- [Source / form](https://echa.europa.eu/information-on-chemicals)

### Compliant CLP label (pictograms + signal word + H/P)

- **required** (required / clp_label)
- How to comply: The label must include: GHS pictograms, the signal word (Danger/Warning), hazard (H) and precautionary (P) statements, and manufacturer details. Required since 2010 (substances) and 2015 (mixtures).
- [Source / form](https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32008R1272)

### Chemical OSH training (substance-specific)

- **required** (required / bhp_training)
- How to comply: Laboratory staff: initial training (general induction + job-specific) + refresher training every 5 years (or every 3 for engineering/technical positions). Documentation kept in personnel files.
- [Source / form](https://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=WDU20040180169)

### BDO registration (Polish Waste Database)

- **not applicable** (not_applicable / bdo_registration)
- How to comply: The verified GHS classification does not indicate classes resulting in hazardous waste — BDO registration for this substance is not required. Verify the EWC code for the specific waste form.
- [Source / form](https://bdo.mos.gov.pl/)

### ADR transport (international agreement)

- **to be verified** (unknown / adr_transport)
- How to comply: No ADR data in the MOL-GOD dataset for this CAS number. Do NOT assume there are no restrictions — before shipping, verify the transport classification in ADR 2025 (Table A) and in section 14 of the safety data sheet (SDS).
- [Source / form](https://unece.org/transport/dangerous-goods/adr-2025-files)

### REACH registration (>1 t/year EU import)

- **conditional** (conditional / reach_registration)
- How to comply: Importers/manufacturers ≥1 tonne/year must register the substance with ECHA (technical dossier + Chemical Safety Report if ≥10 t). Check the ECHA Annex VI / registered substances list.
- [Source / form](https://echa.europa.eu/regulations/reach/registration)

### SVHC notification (Substances of Very High Concern)

- **to be verified** (unknown / svhc_declaration)
- How to comply: SVHC status not verified against the available dataset — check the current ECHA candidate list; do not assume the absence of an entry.
- [Source / form](https://echa.europa.eu/candidate-list-table)

### REACH Annex XIV (authorisation list)

- **to be verified** (unknown / reach_annex_xiv)
- How to comply: Not verified against the ECHA Authorisation List — check REACH Annex XIV.
- [Source / form](https://echa.europa.eu/authorisation-list)

### REACH Annex XVII (use/marketing restrictions)

- **to be verified** (unknown / reach_annex_xvii)
- [Source / form](https://echa.europa.eu/substances-restricted-under-reach)

### OEL — Occupational Exposure Limit in the working environment

- **to be verified** (unknown / nds_workplace)
- How to comply: No NDS data in the MOL-GOD dataset (incomplete set — ~41 of ~600 substances in the list). Absence does NOT mean there is no NDS — check the full list in Dz.U. 2024 poz. 1017 (Regulation of the Ministry of Family and Social Policy of 4 September 2024), and where none exists apply the OEL from EU directives or values recommended by NIOSH/ACGIH.
- [Source / form](https://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=WDU20240001017)

### GIS register (precursors / psychotropics)

- **to be verified** (unknown / gis_register)
- How to comply: Does not appear in the available working set of precursors (list incomplete). Absence is NOT a confirmation — verify against Annex I of Reg. (EC) 273/2004 and the GIS list before placing on the market.
- [Source / form](https://www.gov.pl/web/gis)

### Safety Data Sheet in Polish

- **required** (required / sds_pl)
- How to comply: Requirement: SDS in Polish for trade in PL (Art. 31 REACH + Chemical Substances Act Art. 17).
- [Source / form](https://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=WDU20012112135)


## Data sources

- [PubChem CID 245503](https://pubchem.ncbi.nlm.nih.gov/compound/245503)
- [NIST WebBook](https://webbook.nist.gov/cgi/cbook.cgi?ID=1822-66-8)
- [ChEMBL](https://www.ebi.ac.uk/chembl/g/#search_results/all/query=1822-66-8)

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*Last updated: 2026-09-02 · Generator: MOL-GOD v3.12.33*