Frémy's salt

Frémy's salt, also known as potassium nitrosodisulfonate, is an inorganic compound with the chemical formula K₂[(NO)(SO₃)₂]. It is a red-colored salt used primarily in the field of chemistry for the generation of free radicals in synthetic applications. This compound is named after the French chemist Edmond Frémy, who first synthesized it in the 19th century. Frémy's salt is notable for its stability as a solid, which allows it to be stored and used as a convenient source of radicals.

Properties

Frémy's salt is characterized by its deep red color and high solubility in water. It decomposes in the presence of water, releasing nitrogen gas, sulfate, and hydroxyl radicals. This decomposition is often catalyzed by heat or light, making it a useful reagent in photochemical reactions and thermal initiation processes.

Synthesis

The synthesis of Frémy's salt involves the oxidation of phenylhydrazine with potassium nitrite in the presence of sulfuric acid. The reaction proceeds through the formation of a nitroso compound, which then reacts with bisulfite to form the nitrosodisulfonate ion, a key component of Frémy's salt.

Applications

Frémy's salt has found applications in various areas of chemistry. It is particularly valued in organic synthesis for the generation of radicals, which can initiate polymerization reactions or be used in the synthesis of complex organic molecules. Additionally, its ability to generate radicals under controlled conditions makes it a useful tool in the study of radical-mediated processes and mechanisms.

Safety

Handling Frémy's salt requires caution due to its potential to decompose explosively under certain conditions. It is recommended to store the compound in a cool, dry place and handle it with protective equipment to minimize exposure to its decomposition products.

See also

• Free radical
• Organic synthesis
• Photochemistry