Cleavage of disulfide polymers. III. By disulfides

AbstractA study was made of the cleavage of polymeric disulfide by organic disulfides of different structures in the presence and absence of sodium disulfide. While aliphatic disulfides will cleave polymeric disulfides only in the presence of sodium disulfide, hydroxyethyl disulfide and aromatic disulfides will cause partial cleavage in the absence of inorganic disulfide. It is believed that cleavage results not from a disulfide–disulfide interchange, but from cleavage of the organic disulfide by water to form a RS− anion. Other salts known to cleave disulfide groups promote the cleavage of polymer by butyl disulfide, sodium sulfoxylateformaldehyde being particularly active. Benzothiazyl disulfide and tetraalkylthiuram disulfides reacted to cleave in the absence of sodium disulfide but had no effect when sodium disulfide was present. By carrying out the reaction stepwise, it was found that sodium disulfide reversed the softening action of the disulfide reforming the cleaved linkages. When the disulfide polymer contained terminal thiol groups, tetramethylthiuram disulfide would reform the high polymer by converting thiol terminals to disulfide links. In spite of the known ability of these complex disulfides to dissociate homolytically into radicals and initiate vinyl polymerization, no evidence was found that the cleavage of polymeric disulfides involved RS·radicals.