Triflic acid, trifluoromethanesulfonic acid, is one of the strongest acids; called super acid.
It is about 1000 times stronger than sulfuric acid. Triflic acid is a clear
hygroscopic liquid; completely miscible with water; soluble in polar solvents.
When contacted with moist in air, it forms a hydrated solid. Triflate
(trifluoromethanesulfonate) is the conjugate base
of triflic acid. The parent acid and triflate are versatile reactants and solvents in many organic chemistry. The
most characteristic properties are thermal stability and chemical resistance to oxidation and reduction reactions.
They do not split off fluorine ions, even in a condition of the attack by
strong nucleophiles. Triflic acid does not sulfonate substrates.
Triflic acid, its salts, acid halides, anhydrides and esters are
used as a catalyst for the reactions
of:
- condensation of alcohols
and carboxylic acids
- reaction of aromatic compounds with sulfonyl
chlorides
- cracking of alkanes, alkylation of
alkenes, isomerisation
of alkanes and trans-alkylation of aromatics
- trans-bromination and other
Friedel-Crafts reactions.
Substituted trifluoroborates are alternatives to boronic acids in C-C bond
forming (rhodium catalyzed) and Suzuki reactions. These salts are stable in air
and water. They are excellent leaving groups. They usually don't require adding
either additional ligands or base for cross coupling. They do not form
cyclic anhydrides which boronic acids do readily. Alkyl triflates are very sensitive
to nucleophiles ( SN2 reactions), they must be stored in
dried conditions without water.
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