Solvation, potassium permanganate

Stability and metal ion salt solubilities of the sila-crowns have not been quantitatively evaluated. The sila-17-crown-6 materials offer simple qualitative evidence of complex formation. Potassium permanganate is mixed with chlorobenzene. The salt rapidly settles and no coloration of the chlorobenzene is observed. The addition of 1-2% of the silacrown produces the characteristic deep purple color of solvated potassium permanganate. After 1 hour vinylsilacrown solutions turn brown and a fine percipitate is observed, presumbly due to silacrown promoted oxidation of its own vinyl group. 

In aqueous media the highest yields of alkanediols are obtained using potassium permanganate in very basic solutions". Alternatively, in the presence of phase transfer catalysts such as quaternary ammonium and phosphonium salts100, dimethyl polyethylene glycols101, or crown ethers 102 (Table 10), solvation of the permanganate ion in apolar organic media is also possible ... 

Purple cloud of potassium permanganate diffusing outward as a solid piece dissolves in a beaker of water, seen from above. The solid piece (black) takes up much less space than the solution of potassium permanganate ions. This demonstrates the principle of diffusion, where a liquid or gas will spread out to fill the available space. This in turn demonstrates the fundamental differences between a solid and a gas or liquid. A solid is a rigid, constrained structure, which contrasts with the fluid, chaotic nature of a liquid or gas. The molecules of a solid are bonded, but solvation or melting breaks the bonds between the molecules. (Courtesy of Andrew Lambert Photography/Science Photo Library)... 

The crown ethers and cryptates are able to complex the alkaU metals very strongly (38). AppHcations of these agents depend on the appreciable solubihty of the chelates in a wide range of solvents and the increase in activity of the co-anion in nonaqueous systems. For example, potassium hydroxide or permanganate can be solubiHzed in benzene [71 -43-2] hy dicyclohexano-[18]-crown-6 [16069-36-6]. In nonpolar solvents the anions are neither extensively solvated nor strongly paired with the complexed cation, and they behave as naked or bare anions with enhanced activity. Small amounts of the macrocycHc compounds can serve as phase-transfer agents, and they may be more effective than tetrabutylammonium ion for the purpose. The cost of these macrocycHc agents limits industrial use. 

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