Triflic acid

Last updated
Triflic acid
Triflic-acid Structural Formula V1.svg
TfOH-3D-ball-&-stick.png
TfOH-3D-vdW.png
Names
IUPAC name
Trifluoromethanesulfonic acid
Other names
Triflic acid
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.014.625 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/CHF3O3S/c2-1(3,4)8(5,6)7/h(H,5,6,7) Yes check.svgY
    Key: ITMCEJHCFYSIIV-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/CHF3O3S/c2-1(3,4)8(5,6)7/h(H,5,6,7)
    Key: ITMCEJHCFYSIIV-UHFFFAOYAW
  • C(F)(F)(F)S(=O)(=O)O
Properties
CF3SO3H
Molar mass 150.07121 g/mol
AppearanceColorless liquid
Density 1.696 g/mL
Melting point −40 °C (−40 °F; 233 K)
Boiling point 162 °C (324 °F; 435 K)
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:
GHS-pictogram-acid.svg GHS-pictogram-exclam.svg
Danger
H290, H302, H314, H335, H402
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)
NFPA 704.svgHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 0: Will not burn. E.g. waterInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard ACID: Acid
4
0
2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)
Trifluoromethanesulfonic acid Trifulorometaansulfoonhape.jpg
Trifluoromethanesulfonic acid

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.

Contents

Synthesis

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

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

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

Historical

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

Synthesis Trifluoromethanesulfonic acid 1.svg

Reactions

As an acid

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:

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

Salt and complex formation

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]

Chloride ligands can be converted to the corresponding triflates:

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

Organic chemistry

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

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.

triflic acid condensation reaction TfOH-condensation-2D.png
triflic acid condensation reaction

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

Safety

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.

Related Research Articles

<span class="mw-page-title-main">Acid</span> Chemical compound giving a proton or accepting an electron pair

An acid is a molecule or ion capable of either donating a proton (i.e. hydrogen ion, H+), known as a Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis acid.

<span class="mw-page-title-main">Acid–base reaction</span> Chemical reaction between an acid and a base

In chemistry, an acid–base reaction is a chemical reaction that occurs between an acid and a base. It can be used to determine pH via titration. Several theoretical frameworks provide alternative conceptions of the reaction mechanisms and their application in solving related problems; these are called the acid–base theories, for example, Brønsted–Lowry acid–base theory.

In chemistry, an amphoteric compound is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used.

<span class="mw-page-title-main">Ethylene oxide</span> Cyclic compound (C2H4O)

Ethylene oxide is an organic compound with the formula C2H4O. It is a cyclic ether and the simplest epoxide: a three-membered ring consisting of one oxygen atom and two carbon atoms. Ethylene oxide is a colorless and flammable gas with a faintly sweet odor. Because it is a strained ring, ethylene oxide easily participates in a number of addition reactions that result in ring-opening. Ethylene oxide is isomeric with acetaldehyde and with vinyl alcohol. Ethylene oxide is industrially produced by oxidation of ethylene in the presence of a silver catalyst.

In organic chemistry, an acyl chloride is an organic compound with the functional group −C(=O)Cl. Their formula is usually written R−COCl, where R is a side chain. They are reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride, CH3COCl. Acyl chlorides are the most important subset of acyl halides.

The Brønsted–Lowry theory (also called proton theory of acids and bases) is an acid–base reaction theory which was first developed by Johannes Nicolaus Brønsted and Thomas Martin Lowry independently in 1923. The basic concept of this theory is that when an acid and a base react with each other, the acid forms its conjugate base, and the base forms its conjugate acid by exchange of a proton (the hydrogen cation, or H+). This theory generalises the Arrhenius theory.

An acidic oxide is an oxide that either produces an acidic solution upon addition to water, or acts as an acceptor of hydroxide ions effectively functioning as a Lewis acid. Acidic oxides will typically have a low pKa and may be inorganic or organic. A commonly encountered acidic oxide, carbon dioxide produces an acidic solution when dissolved.

<span class="mw-page-title-main">Triflate</span> Chemical group (–OSO2CF3) or anion (charge –1)

In organic chemistry, triflate, is a functional group with the formula R−OSO2CF3 and structure R−O−S(=O)2−CF3. The triflate group is often represented by −OTf, as opposed to −Tf, which is the triflyl group, R−SO2CF3. For example, n-butyl triflate can be written as CH3CH2CH2CH2OTf.

<span class="mw-page-title-main">Nickel(II) chloride</span> Chemical compound

Nickel(II) chloride (or just nickel chloride) is the chemical compound NiCl2. The anhydrous salt is yellow, but the more familiar hydrate NiCl2·6H2O is green. Nickel(II) chloride, in various forms, is the most important source of nickel for chemical synthesis. The nickel chlorides are deliquescent, absorbing moisture from the air to form a solution. Nickel salts have been shown to be carcinogenic to the lungs and nasal passages in cases of long-term inhalation exposure.

<span class="mw-page-title-main">Sulfonic acid</span> Organic compounds with the structure R−S(=O)2−OH

In organic chemistry, sulfonic acid refers to a member of the class of organosulfur compounds with the general formula R−S(=O)2−OH, where R is an organic alkyl or aryl group and the S(=O)2(OH) group a sulfonyl hydroxide. As a substituent, it is known as a sulfo group. A sulfonic acid can be thought of as sulfuric acid with one hydroxyl group replaced by an organic substituent. The parent compound is the parent sulfonic acid, HS(=O)2(OH), a tautomer of sulfurous acid, S(=O)(OH)2. Salts or esters of sulfonic acids are called sulfonates.

In chemistry, a trimer is a molecule or polyatomic anion formed by combination or association of three molecules or ions of the same substance. In technical jargon, a trimer is a kind of oligomer derived from three identical precursors often in competition with polymerization.

<span class="mw-page-title-main">Rhodium(III) chloride</span> Chemical compound

Rhodium(III) chloride refers to inorganic compounds with the formula RhCl3(H2O)n, where n varies from 0 to 3. These are diamagnetic solids featuring octahedral Rh(III) centres. Depending on the value of n, the material is either a dense brown solid or a soluble reddish salt. The soluble trihydrated (n = 3) salt is widely used to prepare compounds used in homogeneous catalysis, notably for the industrial production of acetic acid and hydroformylation.

<span class="mw-page-title-main">Aromatic sulfonation</span> Chemical reaction which replaces a hydrogen on an arene with sulfonic acid, –NH–SO3H

In organic chemistry, aromatic sulfonation is an organic reaction in which a hydrogen atom on an arene is replaced by a sulfonic acid functional group in an electrophilic aromatic substitution. Aryl sulfonic acids are used as detergents, dye, and drugs.

A salt metathesis reaction is a chemical process involving the exchange of bonds between two reacting chemical species which results in the creation of products with similar or identical bonding affiliations. This reaction is represented by the general scheme:

In inorganic chemistry, sulfonyl halide groups occur when a sulfonyl functional group is singly bonded to a halogen atom. They have the general formula RSO2X, where X is a halogen. The stability of sulfonyl halides decreases in the order fluorides > chlorides > bromides > iodides, all four types being well known. The sulfonyl chlorides and fluorides are of dominant importance in this series.

<span class="mw-page-title-main">Nitrosyl chloride</span> Chemical compound

Nitrosyl chloride is the chemical compound with the formula NOCl. It is a yellow gas that is commonly encountered as a component of aqua regia, a mixture of 3 parts concentrated hydrochloric acid and 1 part of concentrated nitric acid. It is a strong electrophile and oxidizing agent. It is sometimes called Tilden's reagent, after William A. Tilden, who was the first to produce it as a pure compound.

Lanthanide triflates are triflate salts of the lanthanides. These salts have been investigated for application in organic synthesis as Lewis acid catalysts. These catalysts function similarly to aluminium chloride or ferric chloride, but they are water-tolerant (stable in water). Commonly written as Ln(OTf)3·(H2O)9 the nine waters are bound to the lanthanide, and the triflates are counteranions, so more accurately lanthanide triflate nonahydrate is written as [Ln(H2O)9](OTf)3.

<span class="mw-page-title-main">Silver trifluoromethanesulfonate</span> Chemical compound

Silver trifluoromethanesulfonate, or silver triflate is the triflate (CF3SO3) salt of Ag+. It is a white or colorless solid that is soluble in water and some organic solvents including, benzene. It is a reagent used in the synthesis of organic and inorganic triflates.

<span class="mw-page-title-main">Ammoxidation</span> Chemical process for producing nitriles from ammonia and oxygen

In organic chemistry, ammoxidation is a process for the production of nitriles using ammonia and oxygen. It is sometimes called the SOHIO process, acknowledging that ammoxidation was developed at Standard Oil of Ohio. The usual substrates are alkenes. Several million tons of acrylonitrile are produced in this way annually:

In chemistry, decarbonylation is a type of organic reaction that involves the loss of carbon monoxide (CO). It is often an undesirable reaction, since it represents a degradation. In the chemistry of metal carbonyls, decarbonylation describes a substitution process, whereby a CO ligand is replaced by another ligand.

References

  1. 1 2 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. 1 2 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.