Why is CHCl₃ unsuitable as an NMR solvent?

It contains a hydrogen atom, so it would give its own ¹H peak.

What does the number of peaks in a ¹H spectrum tell you?

The number of different proton environments.

What does the area under a ¹H NMR peak show?

The relative number of protons in that environment.

How do you use integration data with a molecular formula?

Find the ratio of the areas, then scale it so the total equals the number of H atoms in the formula.

State the n + 1 rule.

A proton with n adjacent non-equivalent protons gives a signal split into n + 1 peaks.

What splitting pattern do the protons of an ethyl group –CH₂CH₃ show?

The CH₂ is a quartet and the CH₃ is a triplet.

Which ¹H signal comes from the 12 hydrogens in 2,2-dimethylpropane?

One singlet, because all 12 protons are equivalent with no adjacent protons.

Proton NMRAQA A-Level Chemistry: Flashcards

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Which solvents are used for ¹H NMR?

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Which solvents are used for ¹H NMR?: Deuterated solvents (such as CDCl₃) or CCl₄, which contain no ¹H atoms.
Why is CHCl₃ unsuitable as an NMR solvent?: It contains a hydrogen atom, so it would give its own ¹H peak.
What does the number of peaks in a ¹H spectrum tell you?: The number of different proton environments.
What does the area under a ¹H NMR peak show?: The relative number of protons in that environment.
How do you use integration data with a molecular formula?: Find the ratio of the areas, then scale it so the total equals the number of H atoms in the formula.
State the n + 1 rule.: A proton with n adjacent non-equivalent protons gives a signal split into n + 1 peaks.
How many adjacent protons give a doublet?: One.
How many adjacent protons give a triplet?: Two.
How many adjacent protons give a quartet?: Three.
What splitting pattern do the protons of an ethyl group –CH₂CH₃ show?: The CH₂ is a quartet and the CH₃ is a triplet.
What is the ¹H shift range for R–CH₃?: 0.7–1.2 ppm.
What is the ¹H shift range for CH₃ or CH₂ next to C=O?: 2.1–2.6 ppm.
Which ¹H signal comes from the 12 hydrogens in 2,2-dimethylpropane?: One singlet, because all 12 protons are equivalent with no adjacent protons.

Exam questions on Proton NMR

A chemist records ¹H NMR spectra of organic compounds to find how many hydrogen atoms are in each environment. The sample for each spectrum is dissolved in a solvent, and tetramethylsilane (TMS) is added as the standard.
The integration values for the three peaks in the spectrum of an ester, C₄H₈O₂, are 6.0, 4.0 and 6.0 (arbitrary units). Explain how these data are used to work out the relative numbers of equivalent protons.2 marks
The ¹H NMR spectra of aliphatic compounds show splitting of peaks by hydrogen atoms on adjacent carbon atoms. A student is predicting the splitting patterns for 1,1-dichloroethane, CH₃CHCl₂, using the n + 1 rule.
Use the n + 1 rule to explain why the signal from the CH₃ protons in 1,1-dichloroethane is split in the way you chose in part (a).2 marks
Compound R has the molecular formula C₄H₈O₂. Its ¹H NMR spectrum has three peaks: δ = 1.2 (triplet, relative area 3), δ = 2.1 (singlet, relative area 3) and δ = 4.1 (quartet, relative area 2). Shift data (δ / ppm): R–CH₃ 0.7–1.2; CH₃ next to C=O 2.1–2.6; CH₂ bonded to the O of an ester 3.7–4.1.
Explain how the splitting patterns in the spectrum of R show that it contains an ethyl group, –CH₂CH₃, attached to an atom with no hydrogen atoms.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).