Chemistry 9701 · AS & A Level · Atoms, molecules and stoichiometry

Atoms, molecules and stoichiometry — practice question

Allyl chloride is a significant chemical employed in making plastics, pharmaceuticals and pesticides.
(a)[1]

Give the systematic name for allyl chloride.

(b)

Allyl chloride may be made by several different routes. The usual method is chlorination of propene, which occurs by a free-radical substitution mechanism.

(b(i))[1]

In the initiation step of this reaction, chlorine radicals ($\text{Cl}^\bullet$) are generated from $\text{Cl}_2$ molecules. State the conditions needed to start this reaction.

(b(ii))[1]

The propenyl radical, $\text{CH}_2{=}\text{CHCH}_2^\bullet$, is produced in the first propagation stage of the reaction. Write an equation to show how $\text{CH}_2{=}\text{CHCH}_2^\bullet$ is formed in this propagation step.

(b(iii))[1]

Explain why the free-radical substitution reaction produces only a low yield of allyl chloride.

(b(iv))[1]

Allyl chloride can also be made by the substitution reaction below. Suggest the identity of reagent X.

(c)

A sequence of reactions beginning with allyl chloride is shown.

(c(i))[1]

Suggest a reagent that may be used in reaction 1.

(c(ii))[2]

In reaction 2, the organic product from reaction 1 is combined with concentrated $\text{H}_2\text{SO}_4$ and an organic acid, then heated under reflux. State the function of the concentrated $\text{H}_2\text{SO}_4$. Identify the organic acid that is used.

(c(iii))[1]

State the name of the mechanism taking place in reaction 3.

(c(iv))[2]

The organic product from reaction 3 is Y. Y may be hydrolysed with excess aqueous $\text{H}_2\text{SO}_4$ to give Z. The molecular formula of Z is $\text{C}_4\text{H}_8\text{O}_4$. Draw the structure of Z.

(d)[2]

$2$-bromo-$1$-chloropropane, $\text{CH}_3\text{CHBrCH}_2\text{Cl}$, is the main product formed when allyl chloride reacts with $\text{HBr}$. Explain why $2$-bromo-$1$-chloropropane is the major product of this reaction.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: 3-chloroprop-1-ene

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