# Putrescine is a diamine produced when proteins decompose. It has an unpleasant smell and is responsible for the odour of rotting meat. Putrescine contains two amine groups. When putrescine dissolves in water, the solution formed is alkaline. Explain why the solution is alkaline, and describe what would be observed if a sample of this solution were tested with universal indicator solution.

> WJEC A-Level Chemistry (Wales) — 4.6 Amines · Explain · 5 marks

> Putrescine is a diamine produced when proteins decompose. It has an unpleasant smell and is responsible for the odour of rotting meat. Putrescine contains two amine groups.

## Mark scheme (5 marks)

1. Amines contain a lone pair of electrons on the nitrogen atom
2. The lone pair accepts a proton / H⁺ from water
3. This produces hydroxide ions (OH⁻) in solution
4. Excess hydroxide ions make the solution alkaline / raise pH above 7
5. Universal indicator turns blue / blue-green / violet, indicating an alkaline solution

## Key terms

- [amine](https://www.gradenine.co.uk/glossary/amine)
- [alkaline](https://www.gradenine.co.uk/glossary/alkaline)
- [universal indicator](https://www.gradenine.co.uk/glossary/universal-indicator)

## Related

- [Revision notes for WJEC A-Level Chemistry (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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