The 13C NMR spectrum of a molecule shows 5 peaks. What does this tell you about the molecule?
[1 mark]
Total for this question: 1
Chemistry
NMR spectroscopy
AQA 3.3.15
A-level Chemistry (7405) · exam-style practice, examiner-report intelligence and the tools that drill it.
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The topic on one screen
- 13C NMR: the number of peaks = the number of different carbon environments in the molecule.
- 1H NMR: the number of peaks = the number of different proton (hydrogen) environments.
- Chemical shift (delta, in ppm) places each peak; read the fragment it corresponds to straight off the data booklet.
- Integration (1H only): the ratio of peak areas = the ratio of the numbers of H atoms in each environment.
- Splitting (n+1 rule): a peak split into (n+1) lines means n equivalent H atoms on the ADJACENT carbon. A singlet means no H on the neighbouring carbon.
- TMS is the reference (0 ppm): one sharp peak, inert, non-toxic, volatile; the sample is run in a solvent with no 1H (e.g. CDCl3).
Where students actually lose marks
Only about two-thirds linked the number of 13C peaks to the number of carbon environments. It is the most reliable mark in the topic — count the environments, count the peaks, match them.
June 2023 Paper 2 examiner report (Q05.2)
Explaining why a peak is a singlet was well known (M2), but the corresponding structure was harder. Tie the two together: a singlet = no H on the adjacent carbon, and build the structure to fit.
June 2024 Paper 2 examiner report (Q06.4)
The best structure-determination answers analyse each signal systematically; weaker ones reach the right structure but lose marks for not showing how each spectrum feature supports it. Show your reasoning per peak.
June 2022 Paper 2 examiner report (Q06)
Try it — exam-style
Easy
ORIGINAL · after June 2023 Paper 2 Q05.2
Medium
ORIGINAL
A peak in a 1H NMR spectrum is split into a quartet (4 lines). What does this tell you about the hydrogens on the adjacent carbon?
[1 mark]
Total for this question: 1
Medium
ORIGINAL · after June 2024 Paper 2 Q06.4
In the 1H NMR spectrum of methyl ethanoate (CH3COOCH3) both peaks are singlets. Explain why.
[2 marks]
Total for this question: 2
Medium
ORIGINAL · after June 2024 Paper 2 Q06.3
A 1H NMR spectrum has three peaks with an integration ratio of 3 : 2 : 1. State what this ratio represents and suggest which fragment gives the peak integrating to 3.
[2 marks]
Total for this question: 2
Easy
ORIGINAL
State two reasons TMS is used as the reference standard in NMR spectroscopy.
[2 marks]
Total for this question: 2
Questions are written in the style of past AQA papers (source shown on each) — never copied from them.
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