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Narrative
In an Erlenmeyer flask, 2,6-di-tert-butylhydroquinone is dissolved in dichloromethane. Solid potassium permanganate is added, but the purple inorganic salt does not dissolve in the nonpolar dichloromethane. Addition of the cyclic crown ether dibenzo-18-crown-6 causes the potassium permanganate to dissolve and make a purple solution. The color changes to a reddish-brown as a quinone is formed.

Discussion
The cyclic crown ether dibenzo-18-crown-6 complexes with potassium ions, causing the potassium permanganate to dissolve and make a purple solution. The dissolved permanganate oxidizes 2,6-di-tert-butylhydroquinone to reddish-brown 2,6-di-tert-butyl-p-quinone.