Chemistry 9701 · AS & A Level · Hydrocarbons

Hydrocarbons — practice question

As shown in Fig. 4.1, compounds C and D are alkenes that have the same molecular formula, $\mathrm{C_5H_{10}}$.
(a(i))[1]

State the systematic name of D.

(a(ii))[1]

Explain why C and D do not exhibit geometrical (cis/trans) isomerism.

(a(iii))[1]

Draw the structure of a molecule that is a positional isomer of C and D.

(a(iv))[1]

Give the structural formula of the compound produced when D reacts with $\mathrm{H_2(g)}$ in the presence of a Pt catalyst.

(a(v))[1]

C can form an addition polymer. Draw the structure of one repeat unit of this addition polymer.

(b)[2]

The mass spectrum of C has a molecular ion peak at $m/e = 70$. This peak has a relative intensity of $48.7$. The relative intensity of the $[\mathrm{M+1}]$ peak is $2.7$. Show that these data are consistent with the molecular formula of C.

(c(i))[3]

C reacts with HBr to make E. Complete Fig. 4.2 to show the mechanism for this reaction. Draw the organic intermediate, and include charges, dipoles, lone pairs of electrons and curly arrows where needed.

(c(ii))[1]

D reacts with HBr to give F, which is a chiral bromoalkane. Draw the structure of F.

(c(iii))[2]

Explain why reacting HBr with C and D gives different major products.

(d)[3]

C can be used to make H.\n\nOne possible route to H is shown in Fig. 4.5. Reactions 1 and 3 use different parts of C. Some of the products are then combined to form H.\n\nFig. 4.5 does not show any inorganic products from the reactions.\n\nComplete Table 4.1 with the reagents and conditions required for each of the reactions shown in Fig. 4.5.

Worked solution & mark scheme

This 16-mark question has a full step-by-step worked solution and mark scheme. One marking point: 3-methylbut-1-ene is the correct name.

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