# Benzaldehyde is an aromatic carbonyl compound used in food flavouring. It contains a benzene ring attached to an aldehyde functional group. Explain how you could distinguish between benzaldehyde and benzene using chemical tests, and describe what you would observe in each case.

> OCR A-Level Chemistry B: Salters (H433) — 6.1 Aromatic compounds, carbonyls and acids · Explain · 5 marks

> Benzaldehyde is an aromatic compound with the molecular formula C₇H₆O. It has a benzene ring bonded directly to a –CHO (aldehyde) group. Benzene itself contains only carbon and hydrogen and has no carbonyl functional group.

## Mark scheme (5 marks)

1. Fehling's solution (or Tollens' reagent) can be used to test for the aldehyde group
2. Benzaldehyde gives a positive result with Fehling's solution — a brick-red/orange precipitate forms (or silver mirror with Tollens')
3. Benzene gives no reaction / no colour change with Fehling's solution (or Tollens' reagent) because it has no aldehyde functional group
4. The aldehyde group (–CHO) in benzaldehyde is oxidised during the test
5. Benzene does not react because it lacks a functional group that can be oxidised under these conditions / it is relatively unreactive

## Key terms

- [aldehyde](https://www.gradenine.co.uk/glossary/aldehyde)
- [functional group](https://www.gradenine.co.uk/glossary/functional-group)

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](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/benzaldehyde-is-an-aromatic-carbonyl-compound-94494e85) · Published by Druglandscape Ltd.