# Halogenoalkanes are formed when alkanes react with halogens. Explain why alkanes react with halogens to form halogenoalkanes, and describe what happens to the halogen atom in the product. Include in your answer the type of reaction taking place and the condition required for the reaction to occur.

> AQA A-Level Chemistry (7405) — 3.3.3 Halogenoalkanes · Explain · 5 marks

> Methane reacts with chlorine to form chloromethane (a halogenoalkane) and hydrogen chloride. The reaction can be represented as: CH₄ + Cl₂ → CH₃Cl + HCl

## Mark scheme (5 marks)

1. A hydrogen atom in the alkane is replaced by a halogen atom
2. The reaction is called substitution (or a substitution reaction)
3. Ultraviolet (UV) light is required as the condition for the reaction
4. Alkanes are saturated / contain only single carbon–carbon bonds, so addition reactions cannot occur
5. The halogenoalkane product contains a halogen atom bonded to a carbon atom (in place of the hydrogen)

## Key terms

- [halogenoalkane](https://www.gradenine.co.uk/glossary/halogenoalkane)
- [alkane](https://www.gradenine.co.uk/glossary/alkane)

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/halogenoalkanes-are-formed-when-alkanes-react-fa2f2c7f) · Published by Druglandscape Ltd.