--- title: "Nucleophilic Substitution in Haloalkanes" description: "A carbon-halogen bond is polar, so the carbon can be attacked by a species carrying a lone pair. Which halogen is present decides the rate, because bond strength turns out to matter more than polarity" canonical: https://lightmysky.com/learn/science/nucleophilic-substitution-in-haloalkanes-mt_QG-nKlnVvW source: https://lightmysky.com/learn/science/nucleophilic-substitution-in-haloalkanes-mt_QG-nKlnVvW.md retrieved: 2026-09-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Nucleophilic Substitution in Haloalkanes A carbon-halogen bond is polar, so the carbon can be attacked by a species carrying a lone pair. Which halogen is present decides the rate, because bond strength turns out to matter more than polarity. Subject: Science · Area: Chemistry · Ages 16 to 18 Page: https://lightmysky.com/learn/science/nucleophilic-substitution-in-haloalkanes-mt_QG-nKlnVvW ## Ready when they can - Draws the mechanism for hydroxide, for cyanide and for ammonia attacking a haloalkane - Explains why the carbon carries a partial positive charge in the first place - Ranks chloro, bromo and iodo compounds by rate and justifies the order using bond enthalpy - Names the product family for each nucleophile and says why the cyanide route lengthens the carbon chain ## Lesson: Why nucleophiles pick on haloalkanes A carbon-halogen bond is polar because the halogen pulls the shared electrons toward itself. That leaves the carbon electron poor with a partial positive charge. A nucleophile is an electron rich species that donates a pair of electrons to form a new bond, so it heads for exactly that carbon. Every arrow you draw in substitution starts from this one idea. Chloro compounds react slowest, bromo faster, and iodo fastest. The carbon to iodine bond is the weakest and breaks most easily, so bond strength decides the rate. This surprises many learners: the carbon-chlorine bond is the most polar, yet polarity matters less here than how easily the bond breaks. **Example.** Three nucleophiles give three product families. Hydroxide replaces the halogen with an OH group and makes an alcohol in one clean swap. Cyanide bonds through its carbon to make a nitrile, which lengthens the carbon chain by one. Ammonia bonds through nitrogen, and losing a proton leaves an amine behind. **Tip.** The cyanide route is prized in synthesis because it grows the chain. To name any substitution product, find which atom of the nucleophile bonds to carbon: oxygen means alcohol, carbon means nitrile, nitrogen means amine. Rate questions always turn on bond enthalpy, so quote weakest bond first. **Recap.** Polar bond invites the nucleophile, weakest bond wins the race. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Electrophilic Addition to Alkenes](https://lightmysky.com/learn/science/electrophilic-addition-to-alkenes-mt_1RB5nj8zR8) - [Rate Equations and Orders of Reaction](https://lightmysky.com/learn/science/rate-equations-and-orders-of-reaction-mt_1x3ogDKGxC) - [Bond Energies and the Overall Energy Change](https://lightmysky.com/learn/science/bond-energies-and-the-overall-energy-change-mt_VI0_1ogIOy) ## Opens up - [SN1 and SN2: Kinetics, Stereochemistry and What Decides the Route](https://lightmysky.com/learn/science/sn1-and-sn2-kinetics-stereochemistry-and-what-decides-the-route-mt_BiCjJw2eJF) - [Aldehydes and Ketones: Nucleophilic Addition and the Tests That Separate Them](https://lightmysky.com/learn/science/aldehydes-and-ketones-nucleophilic-addition-and-the-tests-that-separate-them-mt_bVcJ0UaXk6) - [Curly Arrows as the Language of Mechanism](https://lightmysky.com/learn/science/curly-arrows-as-the-language-of-mechanism-mt_C0bq2Mu8HT) - [Amines and Amides: Basicity and the Nitrogen Functional Groups](https://lightmysky.com/learn/science/amines-and-amides-basicity-and-the-nitrogen-functional-groups-mt_cGP3ZJ8S6h) - [Elimination and Choosing Between Two Pathways](https://lightmysky.com/learn/science/elimination-and-choosing-between-two-pathways-mt_tRj_kiSS51)