Chemistry 9701 · AS & A Level · Hydrocarbons

Hydrocarbons — practice question

The hydrocarbons A, $\text{C}_4\text{H}_{10}$, and B, $\text{C}_4\text{H}_8$, are both unbranched. A does not decolourise bromine, whereas B decolourises bromine and also shows geometrical isomerism.
(a(i))[1]

Draw the skeletal formula for A.

(a(ii))[2]

The hydrocarbon A, $\text{C}_4\text{H}_{10}$, has a branched isomer. Suggest why unbranched A has a higher boiling point than its branched isomer.

(a(iii))[1]

Give the structural formula for B.

(a(iv))[2]

Explain why B shows geometrical isomerism.

(a(v))[4]

Draw the mechanism for the reaction of B with bromine, $\text{Br}_2$. Include all necessary charges, dipoles, lone pairs and curly arrows.

(a(vi))[1]

Explain the origin of the dipole on $\text{Br}_2$ in this mechanism.

(b(i))[3]

Identify compounds C, D and E.

(b(ii))[1]

Write the equation for the reaction between E and aqueous sodium carbonate.

(c(i))[1]

Name the yellow precipitate produced by the reaction between F and alkaline aqueous iodine.

(c(ii))[2]

Give the structural formulas of F and G.

(c(iii))[1]

Explain what is meant by the term chiral centre.

(d(i))[2]

Identify the bonds responsible for the main peaks above $1500\,\text{cm}^{-1}$ in each spectrum.\n\nSpectrum H.\n\nSpectrum I.

(d(ii))[2]

Name compounds H and I.

Worked solution & mark scheme

This 23-mark question has a full step-by-step worked solution and mark scheme. One marking point: The correct structural formula for the straight-chain isomer of A

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