''p''-Toluenesulfonic acid (PTSA or ''p''TsOH) or tosylic acid (TsOH) is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

with the formula CH₃ C₆H₄ SO₃H. It is a white extremely hygroscopic solid that is soluble in water,

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

s, and other

polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates *Polar climate, the cli ...

organic solvents. The CH₃C₆H₄SO₂ group is known as the

tosyl In organic chemistry, a toluenesulfonyl group (tosyl group, abbreviated Ts or Tos) is a univalent functional group with the chemical formula –. It consists of a tolyl group, –, joined to a sulfonyl group, ––, with the open valence o ...

group and is often abbreviated as Ts or Tos. Most often, TsOH refers to the monohydrate, TsOH^.H₂O. As with other aryl

sulfonic acid In organic chemistry, sulfonic acid (or sulphonic acid) refers to a member of the class of organosulfur compounds with the general formula , where R is an organic alkyl or aryl group and the group a sulfonyl hydroxide. As a substituent, it is k ...

s, TsOH is a strong

organic acid An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO2OH, are ...

. It is about one million times stronger than

benzoic acid Benzoic acid is a white (or colorless) solid organic compound with the formula , whose structure consists of a benzene ring () with a carboxyl () substituent. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin ...

. It is one of the few strong acids that is solid and therefore is conveniently weighed and stored.

Preparation and uses

TsOH is prepared on an industrial scale by the

sulfonation 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. Stoichiometry a ...

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon. It is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) ...

. Common impurities include benzenesulfonic acid and sulfuric acid. TsOH monohydrate contains an amount of water. To estimate the total moisture present as impurity, the Karl Fischer method is used. Impurities can be removed by recrystallization from its concentrated aqueous solution followed by azeotropic drying with toluene. TsOH finds use in

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

as an "organic-soluble" strong acid. Examples of uses include: *

Acetal In organic chemistry, an acetal is a functional group with the connectivity . Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments n ...

ization of an

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl gro ...

. * Fischer–Speier esterification *

Transesterification In organic chemistry, transesterification is the process of exchanging the organic group R″ of an ester with the organic group R' of an alcohol. These reactions are often catalyzed by the addition of an acid or base catalyst. The reaction ca ...

reactions

Tosylates

Alkyl tosylates are

alkylating agent Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effectin ...

s because tosylate is electron-withdrawing as well as a good

leaving group In chemistry, a leaving group is defined by the IUPAC as an atom or group of atoms that detaches from the main or residual part of a substrate during a reaction or elementary step of a reaction. However, in common usage, the term is often limited ...

. Tosylate is a pseudohalide. Toluenesulfonate esters undergo nucleophilic attack or elimination. Reduction of tosylate esters gives the hydrocarbon. Thus, tosylation followed by reduction allows for the deoxygenation of alcohols. Non-classical_7-norbornenyl_Structure

In a famous and illustrative use of tosylate,

2-norbornyl cation In organic chemistry, the term 2-norbornyl cation (or 2-bicyclo .2.1eptyl cation) describes one of the three carbocations formed from derivatives of norbornane. Though 1-norbornyl and 7-norbornyl cations have been studied, the most extensive studie ...

was displaced from the 7-norbornenyl tosylate. The elimination occurs 10¹¹ times faster than the solvolysis of ''anti''-7-norbornyl ''p''-toluenesulfonate. Tosylates are also

protecting group A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis. In man ...

for

s. They are prepared by combining the alcohol with 4-toluenesulfonyl chloride, usually in an

aprotic solvent A polar aprotic solvent is a solvent that lacks an acidic proton and is polar. Such solvents lack hydroxyl and amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Am ...

, often

pyridine Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid w ...

Reactions

* TsOH may be converted to ''p''-toluenesulfonic anhydride by heating with phosphorus pentoxide. * When heated with acid and water, TsOH undergoes

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysi ...

: :CH₃C₆H₄SO₃H + H₂O → C₆H₅CH₃ + H₂SO₄ This reaction is general for

aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used ...

References

{{DEFAULTSORT:Toluenesulfonic Acid, P- Benzenesulfonic acids Reagents for organic chemistry Acid catalysts Sulfonic acids P-Tosyl compounds

Preparation and uses

Tosylates

Reactions

See also

References