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Other names
bis[3-(triethoxysilyl)propyl]tetrasulfide, bis(3-triethoxysilylpropyl)tetrasulfane, Si-69
3D model (JSmol)
ECHA InfoCard 100.049.888
EC Number 254-896-5
Molar mass 538.95
Appearance yellow syrup
Density 1.08 g/cm3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Bis(triethoxysilylpropyl)tetrasulfide is an organosulfur compound with the formula S4[C3H6Si(OEt)3]2 (Et = C2H5). The molecule consists of two trialkoxysilyl propyl groups linked with a polysulfide. It is often sold as a mixture with the trisulfide. The compound is a colorless viscous liquid that is soluble in ordinary organic solvents such as toluene. Commercial samples often are yellowish. The compound is added to rubber compositions that contain silica filler.[1][2]

Synthesis and reactivity[edit]

The compound was first prepared by the reaction of 3-(triethoxysilyl)propyl chloride with sodium tetrasulfide:[3]

Na2S4 + 2 ClC3H6Si(OEt)3 → S4[C3H6Si(OEt)3]2 + 2 NaCl

Bis(triethoxysilylpropyl)tetrasulfide is a bifunctional molecule in that it contains two kinds of reactive functional groups. The tetrasulfide group is a polysulfide, which means that it consists of a chain of sulfur atoms. S-S bonds are susceptible to reduction (to thiols), attachment to metals (e.g., for protection against corrosion), and vulcanization. The triethoxysilyl groups are susceptible to hydrolysis, resulting in cross-linking via sol-gel condensation. In the usual application of this chemical, the hydrolyzed siloxy groups attach to silica particles and the polysufide groups link to the organic polymer.


  1. ^ Kohjiya, Shinzo; Ikeda, Yuko (2000). "Reinforcement of general-purpose grade rubbers by silica generated in situ". Rubber Chemistry and Technology. 73: 534–550. doi:10.5254/1.3547604.
  2. ^ Wolff, Siegfried (1996). "Chemical aspects of rubber reinforcement by fillers". Rubber Chemistry and Technology. 69: 325–346. doi:10.5254/1.3538376.
  3. ^ Thurn, Friedrich; Meyer-Simon, Eugen; Michel, Rudolf "Verfahren zur Herstellung von Organosiliziumverbindungen (Continuous manufacture of bis[3-(triethoxysilyl)propyl] tetrasulfide)" Ger. Offen. (1973), DE 2212239 A1 19731004.