Butan-2-ol and 2-methylpropan-2-ol are isomers with the formula .
(a)
Deduce the number of peaks in the ¹³C NMR spectrum of butan-2-ol.
[1 mark](b)
Explain why 2-methylpropan-2-ol gives only 2 peaks.
[1 mark]Practice · AQA 7405 · Organic analysis
A-level Chemistry NMR questions: interpret spectra with worked answers
Five exam-style questions, from counting environments to deducing a structure from a spectrum.
1 of 5
Chloroethane, , is analysed by ¹H NMR.
(a)
Describe the two signals, giving the splitting and relative integration of each.
[2 marks](b)
In which δ range does the signal appear (data booklet)?
[1 mark]Tetramethylsilane, TMS, , is added to NMR samples.
Give two reasons why TMS is a suitable reference.
[2 marks]An ester has the molecular formula . The diagram shows its H NMR spectrum. The relative integration is shown above each peak.
(a)
Deduce a structural formula for the ester.
[1 mark](b)
Explain how each of the two signals supports your structure.
[2 marks]Compound X, , gives the ¹H NMR spectrum shown. The number above each peak is its relative integration.
(a)
Deduce a structural formula for X.
[2 marks](b)
Deduce the number of peaks in the ¹³C NMR spectrum of this ketone.
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- NMR and structure deductionLesson in A-level Chemistry Pro
Questions people ask
What does the n+1 rule tell you?
A peak from protons with n hydrogens on adjacent carbons splits into n + 1 lines: a CH₃ next to a CH₂ gives a triplet, and the CH₂ next to the CH₃ gives a quartet.
What does the integration of a peak show?
The relative number of hydrogens in that environment, so peaks in the ratio 3 : 2 could be a CH₃ and a CH₂.
Why is TMS used in NMR?
Tetramethylsilane gives one strong peak, set at δ = 0 as the reference, because all 12 of its hydrogens are in the same environment. It is inert and volatile, so it is easy to remove.