| Popis: |
The deterioration of solutions of dithizone in organic solvents is reviewed and shown to be due to a multiplicity of photochemical and oxidative reactions. Bis-1,5-diphenylformazan-3-yl disulphide has been isolated and characterised as a product of the action ( inter alia ) of aqueous iodine upon dithizone or silver dithizonate. Its spontaneous thermal cleavage to give an equimolar mixture of a meso-ionic compound 2,3-diphenyl-2,3-dihydrotetrazolium-5-thiolate and dithizone is shown to explain the partial regeneration of deteriorated solutions of dithizone when treated with reducing agents. The reactions of the disulphide towards a variety of reducing agents and to cleavage by metal cations is reported. The identity of Fischer's diphenylthiocarbazide, Bamberger's tetrazolium betaine and Ogilvie and Corwin's dehydrodithizone with the orange meso-ionic compound obtained from dithizone by using such oxidants as hydrogen peroxide, potassium permanganate, iodobenzenedichloride and iron (III) or thallium (III) was established by ultimate analysis and visual and infrared spectrometry. The behaviour of S-methyldithizone, dithizone, and its known oxidation products towards thin-layer chromatography with a range of solvents is described and the significance of the R F values discussed. |
