Question

An alkene 'A' on ozonolysis gives a mixture of ethanal and pentan-3-one. Write structure and IUPAC name of 'A'.

Answer 1

Given:

An alkene A on ozonolysis gives:

• Ethanal (CH₃CHO)
• Pentan-3-one (CH₃–CH₂–CO–CH₂–CH₃)

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Concept used:

Ozonolysis cleaves the C=C double bond of an alkene, converting each double-bonded carbon into a carbonyl group.

• An aldehyde indicates that the corresponding alkene carbon had at least one hydrogen.
• A ketone indicates that the corresponding alkene carbon was bonded to two alkyl groups.

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Reconstruction of the alkene:

Ethanal corresponds to the fragment:

CH₃–CH=

Pentan-3-one corresponds to the fragment:

=C(CH₂CH₃)₂

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Structure of alkene A:

CH₃–CH = C(CH₂CH₃)₂

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IUPAC name of alkene A:

The longest chain containing the double bond has six carbon atoms.

Double bond position = 2
Ethyl substituent at carbon 3

IUPAC name: 3-Ethylhex-2-ene

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Final Answer:

Structure: CH₃–CH = C(CH₂CH₃)₂
IUPAC name: 3-Ethylhex-2-ene