Bromoalkanes are used widely in industry, although there is increasing concern about their environmental impact. Fig. 4.1 shows a reaction scheme involving 1,2-dibromoethane. [Figure 4.1]

1. (a)Complete Fig. 4.2 to show the mechanism for the formation of 1,2-dibromoethane in reaction 1. Include charges, dipoles, lone pairs of electrons and curly arrows as appropriate. [Figure 4.2][3]
2. (b)The enthalpy change of reaction 1, ΔH = −90.0 kJ mol⁻¹. The enthalpy change of formation of ethene, ΔH = +52.2 kJ mol⁻¹. Calculate the enthalpy change of formation of 1,2-dibromoethane.[1]
3. (c)(i)Complete Fig. 4.1 to: • draw the structure of compound A • name compound B.[2]
4. (c)(ii)Draw the structure of one repeat unit of polymer C in the box.[1]
5. (c)(iii)In reaction 5, compound B reacts with an excess of NaOH dissolved in ethanol. The products are HBr, H₂O and an unsaturated hydrocarbon D. Suggest the identity of D.[1]
6. (d)Compound E is the only isomer of 1,2-dibromoethane. Alkaline hydrolysis of E gives compound F. [Figure of E and F]
7. (d)(i)Identify the type of isomerism shown by E and 1,2-dibromoethane.[1]
8. (d)(ii)Name the homologous series that F belongs to.[1]
9. (d)(iii)Complete Table 4.1 to state what is observed when F reacts with the reagents listed. Table 4.1 | reagent | observation with F | |---|---| | 2,4-dinitrophenylhydrazine (2,4-DNPH reagent) | | | Tollens' reagent | | | alkaline I₂(aq) | |[3]
10. (e)Compound F reacts with reagent G to form compound H. [Figure of F, G, H]. The infrared spectrum of H is shown in Fig. 4.3. [Figure 4.3]. Table 4.2 [Table 4.2]. H also shows a molecular ion peak at m/e = 60 in its mass spectrum.
11. (e)(i)Use the information in (e), Fig. 4.3 and Table 4.2 to deduce the structure of H. Explain your answer fully. [Structure H box][3]
12. (e)(ii)Suggest the role of reagent G.[1]

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