4,4'-Dimethyl diphenyl disulfide is the simplest aromatic–aliphatic disulfide, consisting of two p-tolyl (4-methylphenyl) groups linked by an –S–S– bridge. It is essentially odourless, stable under ambient conditions, freely soluble in hot ethanol, ethyl acetate, dichloromethane and toluene, and practically insoluble in water. Commercial material is supplied ≥99 % pure.
Key physicochemical data:
Melting point: 47–49 °C (lit.)
Boiling point: 297 °C / 20 mmHg; 405 °C / 760 mmHg (predicted)
Density: 1.15 g cm⁻³ (50 °C, solid)
Refractive index: 1.633 (70 °C, melt)
Flash point: 168 °C (closed cup)
Vapour pressure: <0.01 mmHg (25 °C)
Log P (octanol/water): 4.9 (predicted)
Typical uses:
High-temperature lubricant antioxidant and extreme-pressure (EP) anti-wear additive for gear oils and greases.
Slow-release sulfur donor for vulcanising polar rubbers (NR, NBR) and for producing tolyl-based pharmaceutical intermediates.
Model substrate for mechanistic studies on C–S bond activation, radical thiol–disulfide exchange and tolyl-radical chemistry.
Quality specification (commercial grade):
Purity (GC): ≥99 % (dried basis)
Water content (KF): ≤0.2 %
Free thiol (as p-tolyl-SH): ≤0.1 %
Residue on ignition: ≤0.1 %
Heavy metals: ≤20 ppm
Hazard statement:
Causes skin and eye irritation (H315 + H319). Avoid inhalation of dust; use gloves, goggles and adequate ventilation. Store in a cool, dry place away from oxidants and reducing agents. SDS available on request.
