Question

An unsaturated hydrocarbon ‘A’ adds two molecules of H₂ and on reductive ozonolysis gives butane-1,4-dial, ethanal and propanone. Give the structure of ‘A’, write its IUPAC name and explain the reactions involved.

Answer 1

Two molecules of hydrogen add on ‘A’ this shows that ‘A’ is either an alkadiene or an alkyne.

On reductive ozonolysis ‘A’ gives three fragments, one of which is dialdehyde. Hence, the molecule has broken down at two sites. Therefore, ‘A’ has two double bonds. It gives the following three fragments:

OHC – CH₂ – CH₂ – CHO, CH₃CHO and CH₃ – CO – CH₃

Hence, its structure as deduced from the three fragments must be

\[\begin{array}{cc}
\ce{CH3 - CH = CH - CH2 - CH2 - CH = C - CH3}\\
\phantom{.................................}|\\
\phantom{...................................}\ce{CH3}
\end{array}\]
                                           (A)

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