4.9.5 Oxidation

When an alkyne is treated with cold, aqueous potassium permanganate under neutral conditions, the formation of diketone is observed (Scheme 16).

Scheme 16

Terminal alkynes give a keto-aldehyde that quickly oxidizes to an acid (Scheme 17).

Scheme 17

If the reaction mixture becomes warm or too basic, the diketone undergoes oxidative cleavage to carboxylic acids (Scheme 18).

Scheme 18

Ozonolysis of an alkyne cleaves the triple bond to give two carboxylic acids (Scheme 19). This process can be used to determine the position of the triple bond in an unknown alkyne.