What is Haloform reaction?
The haloform reaction is a chemical reaction that involves the transformation of a methyl ketone into a haloform, which is a compound with the formula CHX3 (where X is a halogen atom). This reaction was first reported by Justus von Liebig in 1834, and has since become a widely studied reaction in the field of chemistry..
The haloform reaction is a three-step process that involves the following steps:
- The methyl ketone is treated with excess base and halogenated solvent, forming a halogenated intermediate..
- The halogenated intermediate is then treated with a dehydrating agent, such as phosphorus pentoxide, forming a halonium ion..
- The halonium ion is then hydrolyzed to form the haloform..
The haloform reaction has a wide range of applications in the synthesis of a variety of compounds, including pharmaceuticals, dyes, and fragrances. For example, it has been used to synthesize the anti-inflammatory drug celecoxib, as well as other compounds that have potential medicinal applications..
Summary
The haloform reaction is an important tool in the synthesis of haloforms and has a wide range of applications in the field of chemistry..
Example
The Haloform reaction is a chemical reaction in which a haloform (CHX3, X = Cl, Br, or I) is formed from a methyl ketone or a secondary alcohol. An example of the Haloform reaction is the reaction between acetone and chlorine:
Acetone is treated with chlorine in the presence of a base such as sodium hydroxide..
The chlorine atom attacks the carbonyl carbon of the acetone, forming a tetrahedral intermediate..
The intermediate collapses and a molecule of HCl is eliminated, forming the haloform, CHCl3 (chloroform)
The haloform can then be hydrolyzed by water to form an acid and a halide salt..
Mechanism of reaction
The Haloform reaction is a chemical reaction in which a haloform (CHX3, X = Cl, Br, or I) is formed from a methyl ketone or a secondary alcohol. The mechanism of the reaction can be broken down into the following steps:
The methyl ketone or secondary alcohol is treated with a base, such as sodium hydroxide, to form an enolate ion..
A halogen, such as chlorine or bromine, is then added to the enolate ion, forming a tetrahedral intermediate which collapses to form a haloform and regenerate the base..
The haloform can then be hydrolyzed to form an acid and a halide salt..
