Molar mass 174.24 g/mol | ||
Appearance Dark red, slightly viscous liquid or yellow crystalline powder | ||
Sodium tetrasulfide is an inorganic compound with the formula Na2S4. It is a yellow-orange solid that dissolved with hydrolysis in water. They are precursors to some specialty polymers and intermediates in prototypes of the sodium-sulfur battery.
Contents
Synthesis and structure
It is produced through the reaction between elemental sulfur and sodium hydrosulfide in alcoholic solution:
2NaSH + 4 S → Na2S4 + H2SThe polysulfide anions adopt zig-zag chains of sulfur atoms. The S-S distances are about 2.05 Å and the S-S-S-S dihedral angles are around 90°.
Reactions and applications
Upon treatment with acid, it is converted to hydrogen sulfide and elemental sulfur. Treatment with alkylating agents gives organic polysulfides. In one commercial application, it is used to produce the cross-linking agent bis(triethoxysilylpropyl)tetrasulfide:
Na2S4 + 2 ClC3H6Si(OEt)3 → S4[C3H6Si(OEt)3]2 + 2 NaClSometimes as a mixture with other polysulfides, sodium tetrasulfide is used to produce the polymer called thiokol. The reaction involves alkylation with ethylene chloride:
Na2S4 + C2H4Cl2 → 1/n (C2H4)Sx]n + 2 NaClThese materials, which have the approximate formula (C2H4)Sx]n (x ~ 4), are highly resistant to degradation by solvents and acids.