Chemistry 9701 · AS & A Level · Carbonyl compounds
Carbonyl compounds — practice question
Seven structural isomers share the molecular formula $\text{C}_5\text{H}_{10}\text{O}$, and all of them are carbonyl compounds. Of these, four are aldehydes. These four aldehydes, $A$, $B$, $C$ and $D$, have the following features: aldehyde $A$ has a straight-chain structure, whereas $B$, $C$ and $D$ are branched. Aldehyde $B$ is the only one of the four isomers with a chiral centre, so it occurs as a pair of optical isomers. Aldehyde $C$ contains two methyl groups in its structure, while $D$ contains three.
(a(i))[4]
Give the structural formulae of the four isomers.
(a(ii))[2]
Draw the three-dimensional structures of the two optical isomers of $B$.
(b(i))[3]
Describe a chemical test that would allow you to distinguish any of the four isomers $A$ to $D$ from each of the other three structural isomers of $\text{C}_5\text{H}_{10}\text{O}$ that are carbonyl compounds. In your answer, include any reagents and conditions required and explain what you would observe in each case.
(b(ii))[2]
Describe a test that would produce the same outcome for all seven carbonyl isomers of $\text{C}_5\text{H}_{10}\text{O}$.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The structure of $A$ is $CH_3CH_2CH_2CH_2CHO$.” …