Rearrangements and decompositions of thiobisphenols

Article abstract of DOI:10.1016/S0040-4020(01)83001-5

2,2′-, 2,4′- and 4,4′-Monothiobisphenol separately rearrange in phenol at 180° in the presence of sodium hydroxide to give similar mixtures containing only 2,2′-, 2,4′- and 4,4′-monothiobisphenol in the approximate ratio, 45:45:10. The rearrangements appear to be intermolecular and they are interpreted in terms of polar processes which lead initially to the formation of o- and p-monothiobenzoquinones. 2,2′-Dithiobisphenol, 4,4′-dithiobisphenol and 4,4′-trithiobisphenol under similar conditions are desulphurated with the evolution of hydrogen sulphide also to give mixtures containing only 2,2 - 2,4′- and 4,4′-monothiobisphenol whilst 3,3′-dithiobisphenol is stable in alkaline phenol even after long periods at 180°. Similar initial heterolyses to o- and p-monothiobenzoquinones are suggested as sources of the monothiobisphenols and displacements of sulphide- or hydrosulphide-ions from intermediate benzeneperthiolate ions by carbanions derived from phenol are suggested as sources of the hydrogen sulphide.