NMR spectroscopy is one of the most powerful analytical tools for determining molecular structure.

The ¹H NMR spectrum, including the integration trace, of a ketone with relative molecular mass 86 is shown below.

[Source: SDBS web: www.sdbs.riodb.aist.go.jp (National Institute of

Advanced Industrial Science and Technology, 2014)]

Deduce the structural formula of the compound, justifying your choice.

CH₃CH₂COCH₂CH₃;

Accept full or condensed structural formula.

Any two for [2 max] from:

two H (atom)/proton environments;

3:2/2:3 ratio of atoms in these environments;

one environment an alkyl group / one environment next to a carbonyl;

Accept –CH₃ (0.9–1.0 ppm) / –CO–CH₂– (2.2–2.7 ppm)

Many candidates did elicit the correct structure although the most common error was the incorrect positioning of the carbonyl group. The number of H environments was often established but the ratios of atoms was not seen very often. Many did score a mark for stating a correct shift associated with the methyl group.