Trifluoromethanesulfonic acid

• TfOH
• TFMSS
• TFMSA
• TFSA

Colorless, pungent-smelling, hygroscopic liquid

Liquid

1.71 g · cm -3 ( 20 ° C)

162 ° C

10 hPa ( 55 ° C)

-20

Soluble in water

Attention

1605 mg · kg -1 ( LD50, rat, oral)

Template: Infobox chemical / molecular formula search available

The triflic acid CF3SO3H is a so-called super acid and plays an important role in organic chemistry. Her anion trifluoromethanesulfonate CF3SO3 -, triflate usually called, is of importance. As a conjugate base of a super acid, it is a very stable anion. Trifluoromethylsulfonic finds many uses in organic chemistry, the triflyl is often used as a leaving group and its salts are catalysts. For the triflyl is in specialist publications mostly the abbreviation " OTf " is used; the abbreviation " Tf " is the trifluoromethanesulfonyl - SO2CF3.

• 3.1 salt formation
• 3.2 Reactions in Organic Chemistry

Properties

Physical Properties

Trifluoromethanesulfonic acid is a clear case of standard conditions, colorless liquid with a boiling point of 162 ° C. The connection fumes in the air, with the stable monohydrate (actually Oxoniumtrifluormethylsulfonat ) forms, which has a melting point of 34 ° C and is highly hygroscopic.

Chemical Properties

Trifluoromethanesulfonic acid is soluble in all polar solvents. However, be assumed in esters, ethers, alcohols or ketones are not always that triflic acid is inert to the solvent. Both the acid and the conjugate base, the triflate anion, are most resistant to oxidising and reducing agents, while many other strong acids, oxidizing action, such as perchloric acid or nitric acid. The triflate anion can withstand even strong nucleophiles. In addition, the trifluoromethanesulfonic acid sulfonated not substrates, which can happen with sulfuric quite.

Production and representation

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

Further synthetic options are the electrochemical fluorination ( ECF):

Or the oxidation of Methyltrifluormethylsulfid:

The industrial production is done by electrochemical fluorination of methanesulfonyl chloride. This synthesis is expensive, so alternatives are sought. For example, it is possible to produce trifluoromethanesulfonic of trifluoromethane in strongly acidic or strongly basic solution. It is a radical reaction, such as SO3 or SO2Cl2. However, the yields are low. After favorable syntheses continue to be sought.

Use

Triflic acid and triflate (see below) are used widely in organic chemistry, the acid itself. Primarily as a catalyst in the polymer, fuel, pharmaceutical and sugar industries Protonation of the acid is particularly suitable, as the conjugate base, the triflate, does not react further.

Salt formation

Trifluoromethanesulfonic acid reacts with metal carbonates, among others, and hydroxides in aqueous solution under exothermic formation of the triflate salts. As an example the synthesis of copper (II) triflate, copper (II ) carbonate may be mentioned:

Reactions in organic chemistry,

The reaction of this compound are various and can be displayed only to a small extent here. For more information, please refer to the literature.

From trifluoromethanesulfonic acid mixed anhydrides can be obtained by addition of acid anhydrides or chlorides. They are strong acylating reagents, and can be used, for example, in Friedel- Crafts acylation:

Trifluoromethanesulfonic acid catalyzes the reaction of aromatic compounds with sulfonyl chlorides, probably also through an intermediate anhydride.

In acid-catalyzed dehydration, addition of triflic acid causes an immediate isomerization of alkenes formed in favor of the thermodynamically more stable alkene.

Triflates

The triflate group finds widespread use as a leaving group in organic chemistry. This is due to the extreme stability of the Triflatanions, on the one hand by mesomeric distribution of the negative charge over the three oxygen atoms and sulfur:

In addition, this charge is stabilized by the strong electron-withdrawing effect ( high electronegativity of the three fluorine atoms ) of the trifluoromethyl group. Triflate thus is a better leaving group than for example the related tosylate and mesylate nucleofugal.

Triflate salts are thermally often very stable; the melting points of the anhydrous salts are partially above 350 ° C (Na, Ba, Ag salts). As mentioned above, they can be obtained directly from the reaction of the acid with metal hydroxides or metal in aqueous solution. Triflate salts are increased in recent years and successfully used as Lewis acids in many reactions. The advantage of such salts is their stability in water, which is not the case for many conventional Lewis acids such as AlCl3. Especially suitable are the type Lanthanoidsalze Ln ( OTf ) 3, in particular the scandium Sc (OTf ) 3 This connection can be used for a wide range of reactions as aldol and Diels -Alder reactions ( see further reactions name reaction or Lewis acid).

Safety

Trifluoromethanesulfonic acid is a fuming liquid is corrosive and must be handled with care accordingly. Work under the hood is absolutely necessary.