Chemistry 9701 · AS & A Level · Hydrocarbons

Hydrocarbons — practice question

Long-chain alkanes, for example 4-methylheptane, may be ‘cracked’ to form hydrocarbons with shorter chains.
(a(i))[1]

State the conditions needed for this reaction to proceed.

(a(ii))[1]

Suggest a structure for $B$ ($\text{C}_3\text{H}_8$).

(a(iii))[3]

Compounds $C$, $D$ and $E$ are isomers with molecular formula $ ext{C}_5 ext{H}_{10}$. When heated with concentrated acidified $ ext{KMnO}_4$, compound $C$ yields $ ext{CO}_2$ and compound $F$ ($ ext{C}_4 ext{H}_8 ext{O}_2$). $D$ and $E$ each produce an equal mixture of compounds $G$ ($ ext{C}_2 ext{H}_4 ext{O}_2$) and $H$ ($ ext{C}_3 ext{H}_6 ext{O}_2$). Suggest structures for compounds $C$-$H$.

(a(iv))[1]

Name the isomerism type seen between $D$ and $E$.

(b(i))[1]

Propene, $\text{CH}_3\text{CH}=\text{CH}_2$, reacts with bromine to form 1,2-dibromopropane. How is this reaction usually carried out?

(b(ii))[1]

State what type of reaction is taking place here.

(b(iii))[2]

Draw the mechanism for this reaction, showing the structures of any intermediates as well as any dipoles, lone pairs and curly arrows needed to track electron movement.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: heat with a catalyst, or $\mathrm{Al_2O_3/SiO_2}$

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