# Halogenoalkanes are a family of organic compounds. Explain why chloroalkanes, bromoalkanes and iodoalkanes show different rates of hydrolysis when reacted with warm aqueous sodium hydroxide solution, and describe the trend in reactivity across this series.

> Edexcel A-Level Chemistry (9CH0) — 6.4 Halogenoalkanes · Explain · 5 marks

> Chloroalkanes, bromoalkanes and iodoalkanes all undergo nucleophilic substitution reactions when warmed with aqueous sodium hydroxide solution. The rate at which each type of halogenoalkane reacts differs due to the nature of the carbon–halogen bond.

## Mark scheme (5 marks)

1. The carbon–halogen bond must be broken during hydrolysis
2. Bond strength decreases going from C–Cl to C–Br to C–I
3. A weaker bond is broken more easily, so the reaction is faster
4. Iodoalkanes hydrolyse fastest and chloroalkanes hydrolyse slowest
5. The halide ion (Cl⁻, Br⁻ or I⁻) is released as a product of hydrolysis / the OH⁻ acts as the nucleophile replacing the halogen

## Key terms

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

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