Question

Write down the products of ozonolysis of 1,2-dimethylbenzene (o-xylene). How does the result support Kekulé structure for benzene?

Answer 1

Question:

Write down the products of ozonolysis of 1,2-dimethylbenzene (o-xylene).
How does the result support the Kekulé structure for benzene?

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Step 1: Structure of o-xylene

o-Xylene is 1,2-dimethylbenzene, having two adjacent methyl groups on a benzene ring.

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Step 2: Ozonolysis of o-xylene

Ozonolysis breaks the double bonds present in the benzene ring. Each carbon of the double bond gets converted into a carbonyl group.

On ozonolysis, o-xylene gives the following products:

• Glyoxal (CHO–CHO)
• Methylglyoxal (CH₃–CO–CHO)
• Diacetyl (CH₃–CO–CO–CH₃)

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Step 3: Support for Kekulé structure of benzene

According to Kekulé structure, benzene contains three alternate double bonds.

Ozonolysis cleaves these three double bonds to form three dicarbonyl fragments.

The formation of:
• one molecule of glyoxal,
• one molecule of methylglyoxal, and
• one molecule of diacetyl

clearly indicates the presence of three alternating double bonds in the benzene ring.

Thus, the ozonolysis products of o-xylene support the Kekulé structure of benzene.

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Final Answer:

Ozonolysis of o-xylene gives glyoxal, methylglyoxal, and diacetyl. The formation of these products confirms the presence of three alternate double bonds in benzene, supporting the Kekulé structure.