Chemistry 9701 · AS & A Level · Carbonyl compounds

Carbonyl compounds — practice question

Alkenes react by addition with a $1{:}1$ blend of $ ext{CO}$ and $ ext{H}_2$ to give aldehydes. Fig. 3.1 illustrates the reaction of propene with a $1{:}1$ blend of $ ext{CO}$ and $ ext{H}_2$.
(a(i))[1]

Define what is meant by addition reaction.

(a(ii))[1]

Aldehydes $A$ and $B$ are structural isomers. State the type of structural isomerism shown by $A$ and $B$.

(a(iii))[1]

Name compound $A$.

(a(iv))[1]

The complete reaction of propene with a $1{:}1$ mixture of $ ext{CO}$ and $ ext{H}_2$ gives only $A$ and $B$. The product mixture is made up of $96\%$ $A$ and $4\%$ $B$. Calculate the mass of $A$ produced in this reaction when $5.00 \times 10^3\,\text{kg}$ of propene is used.

(b(i))[4]

$A$ undergoes a nucleophilic addition reaction with a mixture of $ ext{HCN}$ and $ ext{KCN}$, forming compound $C$. Complete the diagram to show the mechanism for this reaction. Include charges, dipoles, lone pairs of electrons and curly arrows, where needed. Draw the structure of the organic intermediate.

(b(ii))[3]

Table 3.1 gives information about three experiments involving $B$. Complete Table 3.1.

(b(iii))[1]

$B$, $ ext{C}_4 ext{H}_8 ext{O}$, is oxidised by acidified potassium manganate(VII). Complete the equation for this reaction. Use $[\text{O}]$ to represent one atom of oxygen from the oxidising agent. $\text{C}_4\text{H}_8\text{O} + \ldots$

(b(iv))[1]

$C$ is a chiral molecule. Circle any chiral centres in the structure of $C$ shown in Fig. 3.2.

(c)[2]

When propene reacts with $ ext{CO}$ and an excess of $ ext{H}_2$, an alkane and a mixture of alcohols are formed instead. The alcohols are isomers of one another. Suggest the molecular formula of the alkane and the alcohols formed under these conditions.

(d(i))[2]

The reaction of ethene, $ ext{C}_2 ext{H}_4$, with a $1{:}1$ mixture of $ ext{CO}$ and $ ext{H}_2$ is shown in equation 1. Equation 1: $\text{C}_2\text{H}_4(g) + \text{CO}(g) + \text{H}_2(g) \rightleftharpoons \text{CH}_3\text{CH}_2\text{CHO}(g)$ At atmospheric pressure a cobalt-based catalyst is used in this reaction. State and explain the effect of using a catalyst on this reaction.

(d(ii))[1]

Explain why the yield of $\text{CH}_3\text{CH}_2\text{CHO(g)}$ increases when the overall pressure of the reaction mixture is increased.

(d(iii))[2]

Use the information in Table 3.2 to calculate the enthalpy change, $\Delta H_r$, of the reaction in equation 1. equation 1: $\text{C}_2\text{H}_4\text{(g)} + \text{CO(g)} + \text{H}_2\text{(g)} \rightleftharpoons \text{CH}_3\text{CH}_2\text{CHO(g)}$

(d(iv))[1]

The reaction mixture is cooled so that $\text{CH}_3\text{CH}_2\text{CHO}$ can be collected as a liquid. Identify all types of van der Waals’ forces present between molecules of $\text{CH}_3\text{CH}_2\text{CHO}$.

Worked solution & mark scheme

This 21-mark question has a full step-by-step worked solution and mark scheme. One marking point: A reaction in which two or more reagents join to produce only one product

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