Date | May 2017 | Marks available | 1 | Reference code | 17M.2.sl.TZ1.5 |
Level | SL | Paper | 2 | Time zone | TZ1 |
Command term | Draw | Question number | 5 | Adapted from | N/A |
Question
This question is about carbon and chlorine compounds.
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.
Markscheme
substitution AND «free-»radical
OR
substitution AND chain
Award [1] for “«free-»radical substitution” or “SR” 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]