2,2′-Thiodisuccinic acid is a thio-ether bis-acid in which two succinic acid units are linked through the central sulfur atom. The molecule contains two stereogenic centers; commercial material is supplied as the racemic mixture (meso : (R,R)/(S,S) ≈ 1 : 1). The compound is freely soluble in water (≥200 g L⁻¹ at 25 °C), sparingly soluble in acetone and ethanol, and practically insoluble in non-polar solvents such as hexane or toluene. It is thermally stable up to 220 °C and shows excellent hydrolytic stability between pH 2 and 10.
Key Physicochemical Data:
Melting point (dec.): 210–213 °C (lit.)
pKₐ (25 °C, H₂O): pKₐ1 3.35, pKₐ2 4.52 (first carboxyl pair); pKₐ3 5.05, pKₐ4 6.18 (second carboxyl pair)
Density: 1.64 g cm⁻³ (20 °C, solid)
Log P (octanol/water, ion-corrected): –1.9 (predicted)
Vapor pressure: <10⁻⁸ mmHg (25 °C)
Typical Uses:
Eco-friendly complexing/seques-tering agent for Fe³⁺, Cu²⁺ and Ca²⁺ in alkaline peroxide bleaching of pulp, textile pretreatment and industrial cleaners.
Building block for biodegradable chelating polymers (polyaspartates, polyitaconates) and sulfur-containing polyester elastomers.
Model ligand for mechanistic studies on metal-catalyzed desulfurization and on thio-ether-directed C–H activation.
Quality Specification (Commercial Grade):
Purity (HPLC, anhydrous): ≥98 %
Water content (KF): ≤0.5 %
Chloride (Cl⁻): ≤100 ppm
Heavy metals (as Pb): ≤20 ppm
Residue on ignition: ≤0.1 %
Hazard Statement:
Non-hazardous under GHS criteria. Dust may cause mechanical irritation to eyes and respiratory tract. Wear dust mask and safety glasses during handling. Store in tightly closed containers in a cool, dry place away from strong oxidizers. SDS available on request.
