In the laboratory, triflic acid is useful in protonations because the conjugate base of triflic acid is nonnucleophilic. It is also used as an acidic titrant in nonaqueous acid-base titration because it behaves as a strong acid in many solvents (acetonitrile, acetic acid, etc.) where common mineral acids (such as HCl or HSO) are only moderately strong.
With a K = , pK = , triflic acid qualifies as a superacid. It owes many of its useful properties to its great thermal and chemical stability. Both the acid and its conjugate base CFSO, known as triflate, resist oxidation/reduction reactions, whereas many strong acids are oxidizing, such as perchloric or nitric acid. Further recommending its use, triflic acid does not sulfonate substrates, which can be a problem with sulfuric acid, fluorosulfuric acid, and chlorosulfonic acid. Below is a prototypical sulfonation, which triflic acid does not undergo:
Triflic acid fumes in moist air and forms a stable solid monohydrate, CFSOH·HO, melting point 34 °C.