Ethane, C₂H₆, reacts with chlorine in sunlight. State the type of this reaction and the name of the mechanism by which it occurs.

Formulate equations for the two propagation steps and one termination step in the formation of chloroethane from ethane.

One possible product, X, of the reaction of ethane with chlorine has the following composition by mass:

carbon: 24.27%, hydrogen: 4.08%, chlorine: 71.65%

Determine the empirical formula of the product.

The mass and ¹H\(\,\)NMR spectra of product X are shown below. Deduce, giving your reasons, its structural formula and hence the name of the compound.

Chloroethene, C₂H₃Cl, can undergo polymerization. Draw a section of the polymer with three repeating units.

substitution AND «free-»radical
OR
substitution AND chain

Award [1] for “«free-»radical substitution” or “S_R” written anywhere in the answer.

[1 mark]

Two propagation steps:
C₂H₆ + •Cl → C₂H₅• + HCl

C₂H₅• + Cl₂ → C₂H₅Cl + •Cl

One termination step:
C₂H₅• + C₂H₅• → C₄H₁₀
OR
C₂H₅• + •Cl → C₂H₅Cl
OR
•Cl + •Cl → Cl₂

Accept radical without • if consistent throughout.

Allow ECF from incorrect radicals produced in propagation step for M3.

[3 marks]

\({\text{C}} = \frac{{24.27}}{{12.01}}\) = 2.021 AND \({\text{H}} = \frac{{4.08}}{{1.01}}\) = 4.04 AND \({\text{Cl}} = \frac{{71.65}}{{35.45}} = 2.021\)

«hence» CH₂Cl

Accept \(\frac{{24.27}}{{12.01}}\) : \(\frac{{4.08}}{{1.01}}\) : \(\frac{{71.65}}{{35.45}}.\)

Do not accept C₂H₄Cl₂. 

Award [2] for correct final answer.

[2 marks]

molecular ion peak(s) «about» m/z 100 AND «so» C₂H₄Cl₂ «isotopes of Cl»

two signals «in ¹H\(\,\)NMR spectrum» AND «so» CH₃CHCl₂
OR
«signals in» 3:1 ratio «in ¹H\(\,\)NMR spectrum» AND «so» CH₃CHCl₂
OR
one doublet and one quartet «in 1H\(\,\)NMR spectrum» AND «so» CH₃CHCl₂

1,1-dichloroethane

Accept “peaks” for “signals”.

Allow ECF for a correct name for M3 if an incorrect chlorohydrocarbon is identified

[3 marks]

Continuation bonds must be shown.

Ignore square brackets and “n”.

Accept     .

Accept other versions of the polymer, such as head to head and head to tail.

Accept condensed structure provided all C to C bonds are shown (as single).

[1 mark]