# A pharmaceutical company is developing a new painkiller. A chemist uses mass spectrometry and infrared spectroscopy to identify the structure of an unknown organic compound isolated during the synthesis process. The mass spectrum shows a molecular ion peak at m/z = 46, and the infrared spectrum shows a broad absorption in the range 2500–3300 cm⁻¹. Explain how mass spectrometry and infrared spectroscopy are used together to identify the unknown compound, and identify the functional group present in the compound.

> Edexcel A-Level Chemistry (9CH0) — 7.1 Mass spectrometry and infrared · Explain · 5 marks

> The unknown compound has a molecular ion peak at m/z = 46 in its mass spectrum. Its infrared spectrum shows a broad absorption in the range 2500–3300 cm⁻¹.

## Mark scheme (5 marks)

1. The molecular ion peak in the mass spectrum gives the relative molecular mass of the compound
2. Fragmentation peaks in the mass spectrum can be used to identify fragments / parts of the molecule
3. Infrared spectroscopy identifies functional groups by matching absorptions to a reference / data table of known absorptions
4. The broad absorption at 2500–3300 cm⁻¹ indicates the presence of an O–H bond in a carboxylic acid / the functional group is a carboxylic acid (–COOH)
5. Using both techniques together provides more complete / reliable identification than either technique alone

## Key terms

- [mass spectrometry](https://www.gradenine.co.uk/glossary/mass-spectrometry)
- [molecular ion peak](https://www.gradenine.co.uk/glossary/molecular-ion-peak)
- [infrared spectroscopy](https://www.gradenine.co.uk/glossary/infrared-spectroscopy)
- [functional group](https://www.gradenine.co.uk/glossary/functional-group)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-pharmaceutical-company-is-developing-a-ab9a5fb5) · Published by Druglandscape Ltd.