''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. The ...

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 c ...

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 on s ...

group and is often abbreviated as Ts or Tos. Most often, TsOH refers to the

monohydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was underst ...

, 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 kn ...

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 rel ...

. 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, wh ...

. 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 of

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) at ...

. 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 An azeotrope () or a constant heating point mixture is a mixture of two or more liquids whose proportions cannot be altered or changed by simple distillation.Moore, Walter J. ''Physical Chemistry'', 3rd e Prentice-Hall 1962, pp. 140–142 This ...

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: * Acetalization 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 grou ...

. * Fischer–Speier esterification * Transesterification 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 effecting al ...

s because tosylate is

electron-withdrawing In chemistry, an electron-withdrawing group (EWG) is a substituent that has some of the following kinetic and thermodynamic implications: *with regards to electron transfer, electron-withdrawing groups enhance the oxidizing power tendency of the ...

as well as a good leaving group. Tosylate is a pseudohalide. Toluenesulfonate esters undergo

nucleophilic attack In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...

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 many ...

for

s. They are prepared by combining the alcohol with

4-toluenesulfonyl chloride 4-Toluenesulfonyl chloride (''p''-toluenesulfonyl chloride, toluene-''p''-sulfonyl chloride) is an organic compound with the formula CH3C6H4SO2Cl. This white, malodorous solid is a reagent widely used in organic synthesis. Abbreviated TsCl or ...

, 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 groups. In contrast to protic solvents, these solvents do not serve as proton donors in hydrogen bonding In chemistry, a hydro ...

, 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 with a d ...

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 reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

: :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 as ...

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