Oxidation of Alkyl Benzene

In this video we want to discuss the oxidation of alkyl benzene using KMnO4 in dilute H2SO4, heat under reflux.

oxidation of alkylbenzene reaction reagents and conditions

The criteria for alkylbenzene to be oxidised to benzoic acid is the alpha carbon (carbon directly bonded to benzene) must have minimum 1 H.

The observation for this reaction will be the decolourisation of purple KMnO4 and formation of white precipitate benzoic acid.

In A Level Chemistry Syllabus, the rest of the groups attached to alpha carbon are usually discarded and we do not need to determine what they are oxidised to, unless it is one carbon then it'll be oxidised to CO2.

Let's take a look at a few examples:

oxidation of alkylbenzene methylbenzene


oxidation of alkylbenzene ethylbenzene

oxidation of alkylbenzene alpha carbon with no hydrogen

Notice for the last example, there is no oxidation since the alpha carbon has no hydrogen attached to it.

Quiz: Oxidation using Different Oxidising Agents

Take a look at this compound.

oxidation of alkylbenzene quiz time

If the above compound is subjected to the following oxidising agents, would they form the same product?

either K2Cr2O7, dilute H2SO4, heat
or KMnO4, dilute H2SO4, heat

Test yourself first and check out this video to find out if you got this correct!

Topic: Benzene, Organic Chemistry, A Level Chemistry, Singapore

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