haloform reaction

chemistry

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

June 29, 2026

Quick Summary

The haloform reaction is a chemical process involving aldehydes with at least one alpha-hydrogen. When treated with halogens like chlorine, bromine, or iodine, under either acidic or basic conditions, the alpha-hydrogen can be replaced by a halogen atom.

If there are three alpha-hydrogens on the same carbon, the reaction proceeds further, cleaving an X₃C^- ion (where X is a halogen). This ion then reacts to form a haloform, which is a compound with the general formula CHX₃, such as chloroform (CHCl₃). This reaction is named the haloform reaction because of the production of these haloform compounds.12

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

2 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

aldehyde
α-Halogenation
This reaction is called the haloform reaction, because X₃C⁻ ions react with water or another acid present in the system to produce compounds of the form X₃CH, which are called haloforms (e.g., CHCl₃ is called chloroform).
Read More
This reaction is called the haloform reaction, because X₃C⁻ ions react with water or another acid present in the system to produce compounds of the form X₃CH, which are called haloforms (e.g., CHCl₃ is called chloroform).
Read More