Organic Disulfides and Polysulfides

Further support for un branched structures in hydrogen polysulfides and polysulfur dichlorides comes from molar volumes, refractions, and viscosities these are discussed in Section V on organic disulfides and polysulfides. 

In the case of hydrogen disulfide, the S—S bond length as determined by Stevenson and Beach (211) from electron diffraction indicates that branching does not occur. Electron diffraction studies by Palmer (184) and Guthrie (188) on disulfur dichloride show an unbranched, nonplanar structure. Smyth (206) has discussed the dipole moments of hydrogen disulfide, disulfur dichloride, and diselenium dichloride on the same basis and Hooge and Ketelaar (145), the vibrational spectra of hydrogen disulfide and disulfur difluoride, dichloride, and dibromide. 

These make up the largest class and display a wide variety of terminal groups, from simple and substituted alkyls and aryls to acyls and amino acid residues. Disulfides are usually quite stable polysulfides are less stable but can, like the disulfides, be obtained in a variety of ways. Schoberl and Wagner (198) have recently reviewed preparative methods for tri-, tetra-, and pentasulfides. Only a few hexasulfides are known for example, dimethyl, diethyl, and dibenzyl hexasulfides which were prepared by Bohme and Zinner (84) from the alkyl hydrogen trisulfides by oxidation with iodine they are yellow oils at room temperature. The bis(thiocarbamyl)-hexasulfides studied by Levi (164) and Blake (28) are crystalline and apparently stable. 

The sulfur-sulfur bond in di- and polysulfides is easily cleaved, particularly by nucleophilic reagents. The reactions lead to interconversions and desulfurations and have often been taken to indicate branching of the sulfur chains, but are actually consistent with unbranched structures (87, 97). 

The literature on structure of organic di- and polysulfides is quite extensive. In the last decade convincing evidence has accumulated in favor of unbranched sulfur chain structures, as contrasted with branched, coordinated ones. 

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Arretz, E., Lopez, F. Method for preparing organic disulfides and polysulfides from mercaptans and sulfur in the presence of heterogeneous styrene-divinylbenzene copolymer catalysts having pendant guanidine or amidine groups. 1996, WO 9721673. 

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