Alcohols with sulfonic acid

Chlorosulfonic acid, particularly with batch operation, is best suited for production of a range of products on a relatively small scale. Chlorosulfonic acid is still used for the sulfonation of fatty alcohols, fatty alcohol/ethoxylates, and related detergent raw materials with OH groups available for the attachment of an S03H group. For example, the reaction of lauryl alcohol with chlorosulfonic acid illustrates for example the chemistry involved ... 

Sulfonate esters usually are prepared through treatment of the alcohol with the acid chloride (sulfonyl chloride) in the presence of pyridine (azabenzene) ... 

The major subgroups of anionic surfactants include the alkali carboxylates (soaps), sulfates, sulfonates, and to a smaller degree, phosphates. The esterification of alcohol with sulfuric acid yields probably the best-studied surfactant, sodium dodecylsulfate or SDS. SDS, a sulfate ester, is an extremely effective emulsifier because of its high-electrostatic repulsion. Other sulfates are, for example, sulfated esters from fatty acids, sulfated ethers, and sulfated fats and oils. Sulfonates stem from the reaction of sulfonic acid with suitable substrates. Members of the class of sulfonates are, for example, sulfonic acid salts or aliphatic sulfonates. Other anionic surfactants include substances such as carboxylated soaps and esters of phosphoric acid. 

The sulfation of alkenes or alcohols with concentrated acid is, on the other hand, an important reaction. Both types of sulfation can yield dialkyl as well as monoalkyl sulfates. Furthermore, sulfation (like sulfonation) will not reach completion if excess water is present ... 

A general esterification reaction consists of reacting an alcohol with an acid in the presence of a catalyst (such as sulfonic acid) to produce the ester and water. This is an equilibrium reaction and leads to low conversion. The catalyst is usually neutralized with inorganic base after the completion of the reaction. If carried out in a countercurrent reactor under two-phase conditions, this reaction has many benefits. For example, conversion of maleic anhydride to dialkyl maleates or fatty acids to fatty acid esters is performed in a column packed with a solid catalyst. Liquid (acid) flows down the column from the top. Alcohol vapor flows upward from the bottom and absorbs water that is formed and carries it up (see Fig. 6.30). The removal of water by the alcohol drives the... 

Sulfates These are the largest and most important class of synthetic surfactants, which were produced by reaction of an alcohol with sulfuric acid, i.e., they are esters of sulfuric acid. In practice sulfuric acid is seldom used and chlorosulfonic or sulfur dioxide/air mixtures are the most common methods of sulfating the alcohol. However, due to their chemical instability (hydrolyzing to the alcohol, particularly in acid solutions), they are now overtaken by the sulfonates, which are chemically stable. 

A new method for the preparation of PEMs is based on cross-linking and by thermally activated bridging of the polymer chains with polyatomic alcohols through condensation reaction with sulfonic acid functions. This was applied to sulfonated poly(ether ether ketone) (SPEEK) and some of the membranes exhibited conductivity higher than 2 x 10 S cm at room temperature. The SPEEK may potentially find applications as PEM materials for fuel cells. 

As mentioned in the preceding section one of the most general methods of synthesis of esters is by reaction of alcohols with an acid chloride or other activated carboxylic acid derivative. Section 3.2.5 included a discussion of two other important methods, namely, reactions with diazoalkanes and reactions of carboxylate salts with alkyl halides or sulfonate esters. There remains to be mentioned the acid-catalyzed reaction of carboxylic acids with alcohols, which is frequently referred to as Fischer esterification ... 

In order to achieve more control of methanol crossover, composite membranes are synthesized. Organic-inorganic composite membranes comprising Nafion with inorganic materials silica, mesoporous zirconium phosphate (MZP) and mesoporous titanium phosphate (MTP) are made as proton-exchange-membrane electrolytes for direct methanol fuel cells (DMFCs) [206] with increase in proton conductivity and low methanol crossover. Composite membranes with mordenite incorporated in polyvinyl alcohol-polystyrene sulfonic acid blend tailored with varying degree of sulfonation also retards the methanol release kinetics considerably [199]. 

Alkyl sulfonates are derivatives of sulfonic acids m which the proton of the hydroxyl group is replaced by an alkyl group They are prepared by treating an alcohol with the appropriate sulfonyl chloride usually m the presence of pyridine... 

Esters. Most acryhc acid is used in the form of its methyl, ethyl, and butyl esters. Specialty monomeric esters with a hydroxyl, amino, or other functional group are used to provide adhesion, latent cross-linking capabihty, or different solubihty characteristics. The principal routes to esters are direct esterification with alcohols in the presence of a strong acid catalyst such as sulfuric acid, a soluble sulfonic acid, or sulfonic acid resins addition to alkylene oxides to give hydroxyalkyl acryhc esters and addition to the double bond of olefins in the presence of strong acid catalyst (19,20) to give ethyl or secondary alkyl acrylates. 

Direct, acid catalyzed esterification of acryhc acid is the main route for the manufacture of higher alkyl esters. The most important higher alkyl acrylate is 2-ethyIhexyi acrylate prepared from the available 0x0 alcohol 2-ethyl-1-hexanol (see Alcohols, higher aliphatic). The most common catalysts are sulfuric or toluenesulfonic acid and sulfonic acid functional cation-exchange resins. Solvents are used as entraining agents for the removal of water of reaction. The product is washed with base to remove unreacted acryhc acid and catalyst and then purified by distillation. The esters are obtained in 80—90% yield and in exceUent purity. 

Substitution Reactions on Side Chains. Because the benzyl carbon is the most reactive site on the propanoid side chain, many substitution reactions occur at this position. Typically, substitution reactions occur by attack of a nucleophilic reagent on a benzyl carbon present in the form of a carbonium ion or a methine group in a quinonemethide stmeture. In a reversal of the ether cleavage reactions described, benzyl alcohols and ethers may be transformed to alkyl or aryl ethers by acid-catalyzed etherifications or transetherifications with alcohol or phenol. The conversion of a benzyl alcohol or ether to a sulfonic acid group is among the most important side chain modification reactions because it is essential to the solubilization of lignin in the sulfite pulping process (17). 

All lnaphthalenesulfonic Acids. The aLkyLnaphthalenesulfonic acids can be made by sulfonation of aLkyLnaphthalenes, eg, with sulfuric acid at 160°C, or by alkylation of naphthalenesulfonic acids with alcohols or olefins. These products, as the acids or their sodium salts, are commercially important as textile auxiUaries, surfactants (qv), wetting agents, dispersants (qv), and emulsifying aids, eg, for dyes (qv), wettable powder pesticides, tars, clays (qv), and hydrotropes. 

Sulfation andSulfamation. Sulfamic acid can be regarded as an ammonia—SO. complex and has been used thus commercially, always in anhydrous systems. Sulfation of mono-, ie, primary and secondary, alcohols polyhydric alcohols unsaturated alcohols phenols and phenolethylene oxide condensation products has been performed with sulfamic acid (see Sulfonation and sulfation). The best-known appHcation of sulfamic acid for sulfamation is the preparation of sodium cyclohexylsulfamate [139-05-9] which is a synthetic sweetener (see Sweeteners). 

Sulfonic acids are prone to reduction with iodine [7553-56-2] in the presence of triphenylphosphine [603-35-0] to produce the corresponding iodides. This type of reduction is also facile with alkyl sulfonates (16). Aromatic sulfonic acids may also be reduced electrochemicaHy to give the parent arene. However, sulfonic acids, when reduced with iodine and phosphoms [7723-14-0] produce thiols (qv). Amination of sulfonates has also been reported, in which the carbon—sulfur bond is cleaved (17). Ortho-Hthiation of sulfonic acid lithium salts has proven to be a useful technique for organic syntheses, but has Httie commercial importance. Optically active sulfonates have been used in asymmetric syntheses to selectively O-alkylate alcohols and phenols, typically on a laboratory scale. Aromatic sulfonates are cleaved, ie, desulfonated, by uv radiation to give the parent aromatic compound and a coupling product of the aromatic compound, as shown, where Ar represents an aryl group (18). 

Anhydrous sulfonic acids, particularly linear alkylben2enesulfonic acids, are typically stored ia stainless steel containers, preferably type 304 or 316 stainless steel. Use of other metals, such as mild steel, contaminates the acid with iron (qv), causiag a darkening of the acid over time (27). The materials are usually viscous oils which may be stored and handled at 30—35°C for up to two months (27). AH other detergent-grade sulfonic acids, eg, alcohol sulfates, alcohol ether sulfates, alpha-olefin sulfonates, and alpha-sulfomethyl esters, are not stored owiag to iastabiUty. These are neutrali2ed to the desired salt. 

Poly(vinyl alcohol) is readily cross-linked with low molecular weight dialdehydes such as glutaraldehyde or glyoxal (163). Alkanol sulfonic acid and poly(vinyl alcohol) yield a sulfonic acid-modified product (164). 

Esterification. Citric acid is easily esterified with many alcohols under a2eotropic conditions in the presence of a catalyst such as sulfuric acid, / -toluenesulfonic acid, or sulfonic acid-type ion-exchange resin. Alcohols boiling above 150°C esterify citric acid without a catalyst (5—8). 

Among the acid catalysts, sulfuric acid, sulfonic acids, and hydrochloric acid are most used. With polyhydric alcohols, sulfuric acid is preferred to hydrochloric acid because of the tendency of hydrochloric acid to form chlorohydrins. 

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