Potassium permanganate, decomposition additives

This is known as the Prout—Tompkins equation and has found application to many systems, in addition to the thermal decomposition of potassium permanganate [465] with which it is often associated. The kinetic behaviour of silver permanganate was somewhat different and in a variation of... 

Decomposition was initiated by the addition of a concentrated aqueous solution of calcium and sodium permanganate to the hydrogen peroxide. The use of potassium permanganate proved ineffective since KMn04 is insufficiently soluble in water and the solution contains inadequate MnO -ions for rapid initiation of the reaction. 

Phenyl -tolyl selenide in aqueous suspension is boiled with potassium permanganate for several hours. The manganese mud is dissolved and the 4-carboxydiphenyl selenoxide precipitated by passing in sulphur dioxide. After filtration the precipitate is macerated with dilute sodium carbonate solution, the products of oxidation being separated in this manner into phenyl p-tolyl selenoxide and 4-carboxydiphenyl selenoxide. Addition of dilute sulphuric acid to the sodium carbonate extract causes the separation of 4-carboxydiphenyl selenoxide, which is crystallised from alcohol. The product is a microcrystalline powder, melting with decomposition at 253° to 255° C. Attempts to resolve it into optically active forms have failed the l-menthylamine salt melts at 220° to 222° C. with decomposition, and the d-a-phenyl-ethylamine salt forms feathery needles, M.pt. 194° to 195° C. with decomposition.3... 

Extension of the scope of the methodology to a full stereocontrol in the addition sequence A in order to obtain either, Z-anti- or l,2-ry -diol units was hampered by the inherent //-selectivity of the addition of 2-TST to a,/3-dialkoxy aldehydes. Control of the selectivity by the use of Lewis acids acting as chelating agents was also foiled by substantial decomposition of 2-TST. This limitation was overcome by conversion of the 7 //-adduct into the syn-isomer via an oxidation-reduction sequence <1989JOC702>. The secondary (Rj-alcohol 457 was oxidized to ketone 461 with potassium permanganate partly solubilized with TDA-1 (tris[2-(2-methoxyethoxy)ethyl]amine). It was proved that under these neutral nonaqueous oxidation conditions no appreciable racemization occurred via exchange... 

The addition of reagents X-Y to carbon-carbon ir-bonds may also proceed via a concerted mechanism in which each new a-bond is formed simultaneously on the same face of the ir-bond. The stereochemistry of such reactions is necessarily syn. For example, the reaction of potassium permanganate, which is purple, with an alkene such as cyclohexene proceeds via si/H-addition of permanganate ion across the ir-bond to give 39, which is colorless. Subsequent decomposition of 39 gives a ds-l,2-diol and manganese dioxide, the brown precipitate that is observed as the other product of the reaction (Eq. 10.19). This decoloration of potassium permanganate by alkenes forms the basis of the Baeyer qualitative test for the presence of carbon-carbon ir-bonds (Sec. 25.8B). 

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