Triflic Acid - Wikipedia

Triflic acid

Names
IUPAC name Trifluoromethanesulfonic acid
Other names Triflic acid
Identifiers
CAS Number	1493-13-6 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:48511 Y
ChemSpider	56192 Y
ECHA InfoCard	100.014.625
PubChem CID	62406
UNII	JE2SY203E8 Y
CompTox Dashboard (EPA)	DTXSID70892979 DTXSID2044397, DTXSID70892979
InChI InChI=1S/CHF3O3S/c2-1(3,4)8(5,6)7/h(H,5,6,7) YKey: 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	150.07121 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	1600 g/L
Vapor pressure	3.2
Acidity (pKa)	−14.7±2.0[1]
Conjugate base	Triflate anion
Viscosity	1.864–1.881 mm2/s at 20 °C
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Causes severe acid burns
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H290, H302, H314, H335, H402
Precautionary statements	P234, P261, P264, P270, P271, P273, P280, P301+P312+P330, P301+P330+P331, P303+P361+P353, P304+P340+P310, P305+P351+P338+P310, P363, P390, P403+P233, P405, P501
NFPA 704 (fire diamond)	4 0 2ACID
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Chemical compound

Triflic acid, the short name for trifluoromethanesulfonic acid, TFMS, TFSA, HOTf or TfOH, is a sulfonic acid with the chemical formula CF3SO3H. It is one of the strongest known acids. Triflic acid is mainly used in research as a catalyst for esterification.[2][3] It is a hygroscopic, colorless, slightly viscous liquid and is soluble in polar solvents.

Synthesis

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

CH 3 SO 3 H + 4 HF ⟶ CF 3 SO 2 F + H 2 O + 3 H 2 {\displaystyle {\ce {CH3SO3H + 4 HF ->CF3SO2F + H2O + 3 H2}}}

The resulting CF3SO2F is hydrolyzed, and the resulting triflate salt is reprotonated. Alternatively, trifluoromethanesulfonic acid arises by oxidation of trifluoromethylsulfenyl chloride:[4]

CF 3 SCl + 2 Cl 2 + 3 H 2 O ⟶ CF 3 SO 3 H + 5 HCl {\displaystyle {\ce {CF3SCl + 2 Cl2 + 3 H2O -> CF3SO3H + 5 HCl}}}

Triflic acid is purified by distillation from triflic anhydride.[3]

Historical

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Trifluoromethanesulfonic acid was first synthesized in 1954 by Robert Haszeldine and Kidd by the following reaction:[5]

Reactions

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As an acid

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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 Ka = 5×1014, pKa = −14.7±2.0,[1] 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, 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:

C 6 H 6 + H 2 SO 4 → SO 3 C 6 H 5 ( SO 3 H ) + H 2 O {\displaystyle {\ce {C6H6 + H2SO4 ->[{\ce {SO3}}] C6H5(SO3H) + H2O}}}

Triflic acid fumes in moist air and forms a stable solid monohydrate, CF3SO3H·H2O, melting point 34 °C.

Salt and complex formation

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The triflate ligand is labile, reflecting its low basicity. Trifluoromethanesulfonic acid reacts exothermically with metal carbonates, hydroxides, and oxides. Illustrative is the synthesis of Cu(OTf)2.[6]

Cu 2 CO 3 ( OH ) 2 + 4 CF 3 SO 3 H ⟶ 2 Cu ( O 3 SCF 3 ) 2 + 3 H 2 O + CO 2 {\displaystyle {\ce {Cu2CO3(OH)2 + 4 CF3SO3H -> 2 Cu(O3SCF3)2 + 3 H2O + CO2}}}

Chloride ligands can be converted to the corresponding triflates:

3 CF 3 SO 3 H + [ Co ( NH 3 ) 5 Cl ] Cl 2 ⟶ [ Co ( NH 3 ) 5 O 3 SCF 3 ] ( O 3 SCF 3 ) 2 + 3 HCl {\displaystyle {\ce {3 CF3SO3H + [Co(NH3)5Cl]Cl2 -> [Co(NH3)5O3SCF3](O3SCF3)2 + 3 HCl}}}

This conversion is conducted in neat HOTf at 100 °C, followed by precipitation of the salt upon the addition of ether.

Organic chemistry

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Triflic acid reacts with acyl halides to give mixed triflate anhydrides, which are strong acylating agents, e.g. in Friedel–Crafts reactions.

CH 3 C ( O ) Cl + CF 3 SO 3 H ⟶ CH 3 C ( O ) OSO 2 CF 3 + HCl {\displaystyle {\ce {CH3C(O)Cl + CF3SO3H -> CH3C(O)OSO2CF3 + HCl}}} CH 3 C ( O ) OSO 2 CF 3 + C 6 H 6 ⟶ CH 3 C ( O ) C 6 H 5 + CF 3 SO 3 H {\displaystyle {\ce {CH3C(O)OSO2CF3 + C6H6 -> CH3C(O)C6H5 + CF3SO3H}}}

Triflic acid catalyzes the reaction of aromatic compounds with sulfonyl chlorides, probably also through the intermediacy of a mixed anhydride of the sulfonic acid.

Triflic acid promotes other Friedel–Crafts-like reactions including the cracking of alkanes and alkylation of alkenes, which are very important to the petroleum industry. These triflic acid derivative catalysts are very effective in isomerizing straight chain or slightly branched hydrocarbons that can increase the octane rating of a particular petroleum-based fuel.

Triflic acid reacts exothermically with alcohols to produce ethers and olefins.

Dehydration gives the acid anhydride, trifluoromethanesulfonic anhydride, (CF3SO2)2O.

Safety

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Triflic acid is one of the strongest acids. Contact with skin causes severe burns with delayed tissue destruction. On inhalation it causes fatal spasms, inflammation and edema.[7]

Like sulfuric acid, triflic acid must be slowly added to polar solvents to prevent thermal runaway.

References

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1. ^ a b Trummal, A.; Lipping, L.; Kaljurand, I.; Koppel, I. A.; Leito, I. (2016). "Acidity of Strong Acids in Water and Dimethyl Sulfoxide". Journal of Physical Chemistry A. 120 (20): 3663–3669. Bibcode:2016JPCA..120.3663T. doi:10.1021/acs.jpca.6b02253. PMID 27115918. S2CID 29697201.
2. ^ Howells, R. D.; McCown, J. D. (1977). "Trifluoromethanesulfonic Acid and Derivatives". Chemical Reviews. 77 (1): 69–92. doi:10.1021/cr60305a005.
3. ^ a b Subramanian, L. R.; Martinez, A. G.; Hanack, M.; Prakash, G. K. S.; Hu, J. (2006). "Trifluoromethanesulfonic Acid". Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289X.rt246.pub2. ISBN 0-471-93623-5.
4. ^ Siegemund, G.; Schwertfeger, W.; Feiring, A.; Smart, B.; Behr, F.; Vogel, H.; McKusick, B. (2000). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. John Wiley & Sons. doi:10.1002/14356007.a11_349. ISBN 3527306730.
5. ^ Haszeldine, R. N.; Kidd, J. M. (1954). "Perfluoroalkyl derivatives of sulphur. Part I. Trifluoromethanesulphonic acid". Journal of the Chemical Society. 1954: 4228–4232. doi:10.1039/JR9540004228.
6. ^ Dixon, N. E.; Lawrance, G. A.; Lay, P. A.; Sargeson, A. M.; Taube, H. (1990). "Trifluoromethanesulfonates and trifluoromethanesulfonato-O complexes". In Angelici, R. J. (ed.). Reagents for Transition Metal Complex and Organometallic Syntheses. Inorganic Syntheses. Vol. 28. pp. 70–76. doi:10.1002/9780470132593.ch16. ISBN 978-0-470-13259-3.
7. ^ "Trifluoromethanesulfonic acid MSDS". ChemCAS.

v t e Hydrogen compounds

H3AsO3 H3AsO4 HArF HAt HSO3F H[BF4] HBr HBrO HBrO2 HBrO3 HBrO4 HCl HClO HClO2 HClO3 HClO4 HCN HCNO H2CrO4/H2Cr2O7 H2CO3 H2CS3 HF HFO HI HIO HIO2 HIO3 HIO4 HMnO4 H2MnO4 H2MoO4 HNC NaHCO3 HNCO HNO HNO2 HNO3 H2N2O2 HNO5S H3NSO3 H2O H2O2 H2O3 H2O4 H2O5 H3PO2 H3PO3 H3PO4 H4P2O7 H5P3O10 H2[PtCl6] H2S H2S2 H2Se H2SeO3 H2SeO4 H4SiO4 H2[SiF6] HSCN HNCS H2SO3 H2SO4 H2SO5 H2S2O3 H3O H2S2O6 H2S2O7 H2S2O8 CF3SO3H H2Te H2TeO3 H6TeO6 H4TiO4 H2Po H[Co(CO)4]