What Is Fluoroacetic Acid?
Fluoroacetic acid is an organic compound with the formula C2H3FO2.
Known as monofluoroacetic acid in IUPAC nomenclature, its CAS number is 144-49-0. The molecular weight is 78.04, and it has a melting point of 95.3 °F (35.2 ℃) and a boiling point of 329 °F (165 ℃). At room temperature, it is a colorless, odorless solid with needle-shaped crystals. Its density is 1.37 g/cm³, and the pKa is 2.586, indicating its acidity. Fluoroacetic acid is soluble in water and ethanol.
Due to its high toxicity, it is classified as a specific poisonous substance.
Uses of Fluoroacetic Acid
Fluoroacetic acid, known for its extreme toxicity, is used in insecticides and rat poison. In humans, it causes convulsions and heart damage, with a lethal dose of 2-5 mg/kg.
Related substances include sodium monofluoroacetate, used in rat poison, and amide monofluoroacetate, used as an insecticide.
Principle of Fluoroacetic Acid
Below is an explanation of fluoroacetic acid’s synthesis method and its toxicity.
1. Synthesis of Fluoroacetic Acid
Fluoroacetic acid esters can be obtained by heating methyl iodoacetate with copper fluoride or mercury fluoride, or by heating methyl chloroacetic acid with potassium fluoride. Fluoroacetic acid is synthesized by hydrolyzing these esters.
Naturally occurring in certain plants, monofluoroacetates (potassium salts) are found in toxic plants, mainly in the southern hemisphere, including the “diphtheria” plant in South Africa.
2. Biotoxicity of Fluoroacetic Acid
Fluoroacetic acid, where one hydrogen atom of acetic acid is replaced with fluorine, exhibits significantly higher toxicity. Its small atomic radius allows it to be mistaken for acetic acid, interfering with the aerobic metabolic pathway. Metabolized to fluorocitric acid, it disrupts the citric acid cycle, a crucial energy production pathway in cells, leading to cell death. It is lethal to any organism with a citric acid cycle in its metabolism, with a human lethal dose of 2-5 mg/kg.
Trifluoroacetic acid, while similarly named, is less toxic and used as a laboratory acid. It should not be confused with fluoroacetic acid (monofluoroacetic acid).
3. Chemical Properties of Fluoroacetic Acid
Upon heating, fluoroacetic acid decomposes, releasing highly toxic fluoride vapors. It reacts with many chemicals to produce toxic and flammable gases. Mixing with strong oxidizers and bases is hazardous and should be avoided.
Types of Fluoroacetic Acid
Due to its extreme toxicity, fluoroacetic acid is rarely used.
Sodium monofluoroacetate, its salt, is sold for research and development but is also regulated due to its toxicity. Trifluoroacetic acid, which replaces all hydrogen atoms in the methyl group of acetic acid with fluorine, is a widely used strong acid in various applications, including HPLC. Despite their similar names, fluoroacetic acid (monofluoroacetic acid) is far more toxic, necessitating caution to avoid confusion between the two.