2-Chloro-5-(methylthio)benzoic acid is a bifunctional aromatic compound that combines a carboxylic acid group with a chlorine atom and a lipophilic methylthio group on the same benzene ring. The chlorine is ortho to the acid, while the methylthio substituent is meta to both the acid and the chlorine, giving the molecule a unique electronic and steric profile.
The compound is freely soluble in polar organic solvents (acetone, ethyl acetate, THF, hot ethanol) and only sparingly soluble in water (≈ 20 mg L⁻¹ at 25 °C).
Key physical data:
Melting point: 165–168 °C
Predicted b.p.: 365 °C (760 mmHg)
Predicted pKa (carboxylic): 3.8
Predicted log P: 3.2
Flash point: >150 °C
The material is thermally robust and can be stored at room temperature in a tightly closed, light-resistant container for at least 24 months without detectable degradation.
Typical uses:
Central building block for the synthesis of benzothiazine-1,1-dioxide COX-2 inhibitors (analogues of rofecoxib) via intramolecular cyclisation after oxidation of the thio-ether to sulfone.
Precursor to 2-chloro-5-(methylsulfonyl)benzoic acid, a key intermediate for the herbicide chloransulam-methyl and other acetolactate-synthase inhibitors.
Ligand scaffold for Pd-catalysed C–H activation chemistry and for the preparation of atropisomeric catalysts exploiting the steric hindrance between the ortho-chloro and meta-thioether substituents.
Quality specification (commercial grade):
Purity (HPLC, area %): ≥98 %
Water content (KF): ≤0.3 %
Residue on ignition: ≤0.1 %
Heavy metals (ICP-MS): ≤10 ppm
Particle size: D₉₀ ≤ 150 µm (micronised grade on request)
Hazard statement:
Causes skin and eye irritation (H315 + H319). May cause respiratory irritation (H335). Avoid breathing dust; wear P2 or better particulate filter, safety goggles and nitrile gloves. SDS available on request.
