Chemistry 9701 · AS & A Level · 6.1

6.1 — practice question

Fig. 4.1 illustrates how propane, $\mathrm{C_3H_8}$, may be changed into propanoic acid, $\mathrm{CH_3CH_2COOH}$. In reaction 1, sunlight is needed: $\mathrm{C_3H_8 + Cl_2 \rightarrow CH_3CH_2CH_2Cl + HCl}$. This reaction proceeds through initiation, propagation and termination stages.
(a(i))[1]

Name the mechanism represented in reaction 1.

(a(ii))[3]

Complete the mechanism for reaction 1. Write equations to show the stages of the mechanism. Initiation: $\mathrm{Cl_2 \rightarrow 2Cl\bullet}$. Complete propagation 1, propagation 2 and a termination step that produces $\mathrm{CH_3CH_2CH_2Cl}$.

(a(iii))[1]

Reaction 1 begins with the bond fission of $\mathrm{Cl_2}$. State the type of bond fission shown in the initiation stage.

(a(iv))[1]

Compound Q is a by-product of reaction 1. The displayed structure of Q is shown. Name Q.

(a(v))[2]

The molecular formula of Q is $\text{C}_3\text{H}_6\text{Cl}_2$. Identify the types of structural isomerism and stereoisomerism that a molecule with molecular formula $\text{C}_3\text{H}_6\text{Cl}_2$ can show.

(b)[1]

State the reagent and solvent required for reaction 2.

(c(i))[1]

Reaction 3 takes place when $\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}$ is heated under reflux with acidified potassium dichromate(VI) solution. State the colour change that takes place in the reaction mixture.

(c(ii))[1]

Construct an equation to represent reaction 3. Use $[\text{O}]$ to represent an atom of oxygen from the oxidising agent.

(d(i))[1]

$\text{CH}_3\text{CH}_2\text{COOH}$ reacts with an unsaturated alcohol R to form unsaturated ester S. State the type of reaction that forms S.

(d(ii))[3]

The infrared spectrum of S is shown in Fig. 4.2. Three absorptions in the infrared spectrum confirm that S is an ester and is unsaturated. Write 1, 2 or 3 on Fig. 4.2 against each of these three absorptions. Complete Table 4.1 to show which bond is responsible for each absorption that you have identified in Fig. 4.2.

(d(iii))[1]

The mass spectrum of S shows the peaks in Table 4.3. Use Table 4.3 to calculate the number of carbon atoms in S.

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