[16222-66-5] · O12S3Tl2 · Thallium(III) Sulfate · (MW 696.97)
Physical Data: mp 102-105 °C.
Solubility: sol water, organic solvents.
Form Supplied in: generally prepared in situ; commercially available.
Handling, Storage, and Precautions: all thallium compounds are extremely toxic to inhalation, skin contact, and ingestion. Toxicity is cumulative. Extreme caution should be used when handling these materials. Use in a fume hood.
Thallium(III) sulfate is a versatile oxidant, although most reports have been in kinetic and mechanistic studies of thallium(III) salts in general. The reagent is usually formed in situ by dissolving another thallium compound (e.g. Thallium(I) Hydroxide or Tl2O3) in sulfuric acid. Thus formed, thallium(III) sulfate has been used to oxidize both alkenes and aliphatic ketones. In the latter case, a-hydroxy ketones result.2 The oxidation of alkenes can result in either vicinal diols or carbonyl compounds. Oxidation of ethylene by thallium(III) sulfate has been investigated3 from a mechanistic viewpoint. In a kinetic study,4 the oxidation of methylpentenes with this reagent was reported (eq 1). Good yields of a mixture of the carbonyl product and the vicinal diol were obtained.
The oxidation of cyclohexenes with thallium sulfate has also been studied.5 Thus thallium(III) sulfate oxidation of t-butylcyclohexene provides primarily the trans-diol (1) with lesser amounts of the isomeric byproducts shown (eq 2).
An interesting variation of alkene oxidation by thallium(III) sulfate has been demonstrated in a preparation of 3-chromanols (eq 3).6 The alkylthallium salt postulated as an intermediate in the oxidation is susceptible to intramolecular attack by the aromatic ring, thus forming the ether. In the case of R = NO2, the aromatic ring was sufficiently deactivated by the nitro group to prevent cyclization, resulting in a mixture of the methyl ketone (2) and the diol (3) (eq 4).
Mukund P. Sibi
North Dakota State University, Fargo, ND, USA
Nancy E. Carpenter
University of Minnesota, Morris, MN, USA