CAIE A-Level Chemistry 37.3.2 Predicting Carbon-13 NMR Peaks

Practise predicting carbon-13 NMR peak counts by grouping equivalent carbons through molecular symmetry.

Exam points

label every carbon in the structure and group carbons related by molecular symmetry into one environment
count one 13C peak per distinct environment, not one per carbon atom or carbon type name
compare isomers by finding the symmetry change that makes their predicted peak counts different

[Maximum number: 1]

Asparagine is an amino acid that contains a chiral carbon atom and displays stereoisomerism.

Separate samples of asparagine are dissolved in $\mathrm{CDCl}_{3}$ and analysed using carbon-13 and proton $\left({ }^{1} \mathrm{H}\right)$ NMR spectroscopy.

Fig. 6.1

Predict the number of peaks seen in the carbon-13 and proton ( ${ }^{1} \mathrm{H}$ ) NMR spectra of asparagine.

Table for Question 37.3.2—Carbon-13 NMR peak count question 1 — CAIE A-Level Chemistry A2

& carbon-13 NMR & proton NMR

number of peaks in $\mathrm{CDCl}_{3}$ & 4 & 5

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37.3.2—Carbon-13 NMR peak count question 1