We”ll look at the reaction with ethene. Other alkenes react in just the same way. Manganate(VII) ions are a strong oxidizing agent, and in the first instance oxidize ethene to ethane-1,2-diol (old name: ethylene glycol). Looking at the equation purely from the point of view of the organic reaction:
The products are known as carbonyl compounds because they contain the carbonyl group, C=O. Carbonyl compounds can also react with potassium manganate(VII), but how they react depends on what is attached to the carbon-oxygen double bond. So we need to work through all the possible combinations.
If both attached R groups in the products are alkyl groups
Carbonyl compounds which have two hydrocarbon groups attached to the carbonyl group are called ketones. Ketones aren”t that easy to oxidize, and so there is no further action. (But see note in red below.) If the groups attached either side of the original carbon-carbon double bond were the same, then you would end up with a single ketone. If they were different, then you would end up with a mixture of two. For example:
If a product has one hydrocarbon group and one hydrogen
For example, suppose the first stage of the reaction was: