Chemistry 9701 · AS & A Level · Hydrocarbons

Hydrocarbons — practice question

Bromoalkanes have many industrial uses, but worries about their effect on the environment are growing. Fig. 4.1 presents a reaction scheme involving 1,2-dibromoethane.
(a)[3]

Complete Fig. 4.2 to show how 1,2-dibromoethane is formed in reaction 1. Include charges, dipoles, lone pairs of electrons and curly arrows as appropriate.

(b)[1]

For reaction 1, $\\Delta H_r$ is $-90.0\\,\\text{kJ mol}^{-1}$. For ethene, $\\Delta H_f$ is $+52.2\\,\\text{kJ mol}^{-1}$. Calculate the enthalpy change of formation of 1,2-dibromoethane.

(c(i))[2]

Complete Fig. 4.1 by drawing the structure of compound A and giving the name of compound B.

(c(ii))[1]

Draw one repeat unit of polymer C in the box.

(c(iii))[1]

In reaction 5, compound B reacts with an excess of NaOH dissolved in ethanol. The products are HBr, H$_2$O and an unsaturated hydrocarbon D. Suggest the identity of D.

(d(i))[1]

Compound E is the sole isomer of 1,2-dibromoethane. Identify the type of isomerism shown by E and 1,2-dibromoethane.

(d(ii))[1]

Name the homologous series to which F belongs.

(d(iii))[3]

Complete Table 4.1 to state the observations when F reacts with the reagents listed: 2,4-dinitrophenylhydrazine (2,4-DNPH reagent), Tollens’ reagent, and alkaline I$_2$(aq).

(e(i))[3]

H also has a molecular ion peak at $m/e = 60$ in its mass spectrum. Use the information in (e), Fig. 4.3 and Table 4.2 to deduce the structure of H. Explain your answer fully.

(e(ii))[1]

Suggest the function of reagent G.

Worked solution & mark scheme

This 17-mark question has a full step-by-step worked solution and mark scheme. One marking point: Dipole induced within $\\mathrm{Br}_2$

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