CF3SO2H

CF₃SO₂H, commonly known as triflic acid, is a strong superacid with the chemical formula CH₃F₃O₃S. It is a colorless, hygroscopic liquid that is highly soluble in water and many organic solvents. Triflic acid is notable for its exceptional acidity, surpassing that of sulfuric acid (H₂SO₄) and other common strong acids. Its acidity is attributed to the strong electron-withdrawing effect of the trifluoromethyl group (CF₃), which stabilizes the conjugate base (CF₃SO₂O⁻) through inductive and resonance effects.

Synthesized industrially, triflic acid is typically produced by the reaction of trifluoromethanesulfonyl fluoride (triflic fluoride) with water or an alcohol. It is widely used in organic synthesis as a catalyst for various reactions, including Friedel-Crafts alkylations, esterifications, and sulfonations. Its ability to generate highly reactive intermediates, such as triflate anions (CF₃SO₂O⁻), makes it valuable in the preparation of triflates, which are useful in cross-coupling reactions like the Suzuki and Stille couplings.

Beyond organic chemistry, triflic acid finds applications in materials science, electrochemistry, and as a solvent for certain reactions. It is also employed in analytical chemistry for derivatization techniques. Due to its corrosive and hygroscopic nature, handling triflic acid requires appropriate safety precautions, including the use of protective equipment and controlled environments.

The physical properties of triflic acid include a boiling point of approximately 162°C and a melting point of −35°C. Its high thermal stability and low volatility contribute to its utility in various chemical processes. Research into triflic acid continues, exploring its potential in emerging fields such as catalysis and sustainable chemistry.