Triflic acid

Trifluoromethanesulfonic acid

Names
IUPAC name Trifluoromethanesulfonic acid
Other names Triflic acid
Identifiers
CAS Number	1493-13-6 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:48511 Y
ChemSpider	56192 Y
ECHA InfoCard	100.014.625
PubChem CID	62406
InChI InChI=1S/CHF3O3S/c2-1(3,4)8(5,6)7/h(H,5,6,7) Y Key: ITMCEJHCFYSIIV-UHFFFAOYSA-N Y InChI=1/CHF3O3S/c2-1(3,4)8(5,6)7/h(H,5,6,7) Key: ITMCEJHCFYSIIV-UHFFFAOYAW
SMILES C(F)(F)(F)S(=O)(=O)O
Properties
Chemical formula	CF3SO3H
Molar mass	150.08 g/mol
Appearance	Colorless liquid
Density	1.696 g/mL
Melting point	−40 °C (−40 °F; 233 K)
Boiling point	162 °C (324 °F; 435 K)
Solubility in water	Miscible
Acidity (pKa)	-14.7 (±2.0)
Hazards
Main hazards	Corrosive, eye irritant
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Trifluoromethanesulfonic acid, also known as triflic acid, TFMS, TFSA, HOTf or TfOH, is a sulfonic acid with the chemical formula CF₃SO₃H. It is one of the strongest acids. Triflic acid is mainly used in research as a catalyst for esterification. It is a hygroscopic, colorless, slightly viscous liquid and is soluble in polar solvents.

Trifluoromethanesulfonic acid is produced industrially by electrochemical fluorination (ECF) of methanesulfonic acid:

The resulting CF₃SO₂F is hydrolyzed, and the resulting triflate salt is preprotonated. Alternatively, trifluoromethanesulfonic acid arises by oxidation of trifluoromethylsulfenyl chloride:

Triflic acid is purified by distillation from triflic anhydride.

Trifluoromethanesulfonic acid was first synthesized in 1954 by Haszeldine and Kidd by the following reaction:

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 H₂SO₄) are only moderately strong.

With a K_a = 5 × 10¹⁴, pK_a −14.7 (±2.0), 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 CF₃SO−
3, known as triflate, resist oxidation/reduction reactions, whereas many strong acids are oxidizing, e.g. 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 HOTf does not undergo: