Aromatics Sulfonic acids

Most phenohc foams are produced from resoles and acid catalyst suitable water-soluble acid catalysts are mineral acids (such as hydrochloric acid or sulfuric acid) and aromatic sulfonic acids (63). Phenohc foams can be produced from novolacs but with more difficulty than from resoles (59). Novolacs are thermoplastic and require a source of methylene group to permit cure. This is usually suppHed by hexamethylenetetramine (64). 

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). 

Sulfonic acids may be hydrolytically cleaved, using high temperatures and pressures, to drive the reaction to completion. As would be expected, each sulfonic acid has its own unique hydrolytic desulfonation temperature. Lower alkane sulfonic acids possess excellent hydrolytic stability, as compared to aromatic sulfonic acids which ate readily hydrolyzed. Flydrolytic desulfonation finds use in the separation of isomers of xylene sulfonic acids and other substituted mono-, di-, and polysulfonic acids. 

Miscellaneous Reactions. Aromatic sulfonic acid derivatives can be nitrated using nitric acid [52583-42-3] HNO, ia H2SO4 (19). Sultones may be treated with hydrazine derivatives to give the corresponding ring-opened sulfonic acid (20). 

The term novolac refers to the early use of phenolic to replace expensive shellac-based coatings. Novolacs are now those resins made at formaldehyde-to-phenol molar ratios of less than one-to-one. They are generally, though not always, manufactured under acidic conditions. Sulfuric or oxalic acids are most often chosen as catalyst though aromatic sulfonic acids and phosphoric acid are also quite common. Many other acids are used for special purposes. The finished novolac resin is incapable of further polymerization or crosslinking and therefore... 

Methyl esters of aromatic sulfonic acids (S020CH3)... 

Some green algae are able to use aromatic sulfonic acids (Figure 2.4a) (Soeder et al. 1987) and aliphatic sulfonic acids (Figure 2.4b) (Biedlingmeier and Schmidt 1983) as sources of sulfur. Cultures of Scenedesmus obliquus under conditions of sulfate limitation metabolized naphthalene-l-sulfonate to l-hydroxy-naphthalene-2-sulfonate and the gluco-side of naphth-l-ol (Kneifel et al. 1997). These results are consistent with formation of a 1,2-epoxide followed by an NIH shift. 

Reactions involving organic substances have some special features. Many of these substances are poorly soluble in aqueous solutions. Sometimes their solubilities can be raised by adding to the solution the salts of aromatic sulfonic acids with cations of the type [NHJ or alkali metal ions. These salts have a salting-in effect on poorly soluble organic substances. In many cases solutions in mixed or nonaque-ous solvents (e.g., methanol) are used. Suspensions of the organic substances in aqueous solutions are also useful for electrosynthesis. 

Dimethyl-aminopropyl Aromatic Sulfonic Acid Functionality... 

Imidazolides of aromatic sulfonic acids react much more slowly in alcoholysis reactions than the carboxylic acid imidazolides. Although the reaction with phenols is quantitative when a melt is heated to 100 °C for several hours, with alcohols under these conditions only very slight alcoholysis is observed. In the presence of 0.05 equivalents (catalytic amount) of sodium ethoxide, imidazole sodium, of NaNH2, however, imidazolides of sulfonic acids react with alcohols almost quantitatively and exothermically at room temperature in a very short time to form sulfonic acid esters (sulfonates). (If the ratio of sulfonic acid imidazolide to alcoholate is 1 2, ethers are formed see Chapter 17). The mechanism of catalysis by base corresponds to that operative in the synthesis of carboxylic esters by the imidazolide method. Because of the more pronounced nucleophilic character of alkoxide ions, sulfonates can also be prepared in good yield by alcoholysis of their imidazolides in the presence of hydroxide ions i.e., with alcoholic sodium hydroxide. 45 Examples of syntheses of sulfonates are presented below. 

Aminolyses of the imidazolides of aromatic sulfonic acids require prolonged heating with a primary amine at temperatures above 100 °C in a sealed tube to generate sulfonamides in good yield. 

Excess acidity correlations have been used to show that some aromatic sulfonic acid desulfonations have an A-SE2 mechanism.188,189 This mechanism (alternative terminologies are Ad-E2 and A(E) +A(N))190 has also been found to apply to the hydration of acetylene itself,191 to ynamines192 and to many other alkynes,193-195 as well as to many different alkenes196-199 and vinyl ethers.200-203 The excess acidity method has been used to evaluate aA values for several alkene hydrations.204 205... 

H. Y. Lin, G. Gonyea, S. Killeen, and S. K. Chowdhury. Negative Fast Atom Bombardment Ionization of Aromatic Sulfonic Acids Unusual Sample-Matrix Interaction. Rapid Commun. Mass Spectrom., 14(2000) 520-522. 

The crude pigment may also be treated with an aromatic sulfonic acid (such as toluene sulfonic acid, xylene sulfonic acids, m-nitrobenzene sulfonic acid) in sulfuric acid or with nitric acid at 80°C to yield a somewhat redder yellow transparent modification of flavanthrone [22],... 

Production of the crude pigment is followed by finishing. The options include milling the material with salt in a ball mill in the presence of an organic solvent, or treating it similarly in a kneader, or producing a 60 to 90% sulfuric acid slurry, or using aromatic sulfonic acids. 

Except for these studies of their protonation behavior, almost the only other aspect of the chemistry of sulfonic acids that has been investigated to any extent from a mechanistic point of view is the desulfonation of aromatic sulfonic acids or sulfonates. Since this subject has been well reviewed by Cerfontain (1968), and since the reaction is really more of interest as a type of electrophilic aromatic substitution than as sulfur chemistry, we shall not deal with it here. One should note that the mechanism of formation of aromatic sulfonic acids by sulfonation of aromatic hydrocarbons has also been intensively investigated, particularly by Cerfontain and his associates, and several... 

Related structures are the pseudoalterobactins A and B from Pseudoalteromonas sp. (Fig. 8,28,29) (7Si), one of the rare examples of bacterial metabolites containing an aromatic sulfonic acid (40). Chiralities of the constituents were not determined. 

Hydrogen fluoride has been used to produce both sulfonic acids and sulfones. Sulfuric acid, fluorosulfonic acid, and aromatic sulfonic acids... 

Allhough rtol shown, the nitrogen atom of the sulfonic acid is probably protonated, or even sLilfonated. under the reaction conditions, exaggerating the steric problems experienced by the substituent at C-8. The mechanism of the desuifonation ol aromatic sulfonic acids occurs via the reverse of the sulfonation process. 

Under extreme conditions of heat and in an acidic environment, aromatic sulfonic acids can revert to sulfuric acid and an aromatic compound. 

Originality Proton-conducting membranes consisting of aromatic sulfonic acid block... 

Cleanup of macrolides and lincosamides from coextracted material can also be accomplished with solid-phase extraction columns. Nonpolar sorbents such as XAD-2 resin (148) or reversed-phase sorbents (133, 134, 137, 141, 142) are usually employed in solid-phase extraction. In the latter case, ion-pairing with pentanesulfonic acid can also be applied for enhancing retention onto the hydro-phobic Ci8 material (154). However, these sorbents are not always effective for efficient cleanup of liver and kidney extracts. The basic character of macrolides and lincosamides suggests that cation-exchange sorbents such as aromatic-sulfonic acid (145,147), or polar sorbents such as silica (144,152,153), aminopropyl (139), or diol (149-151), can be powerful alternative approaches for isolation and/or cleanup of these compounds. 

Elimination of coextracted materials and concentration of tetracyclines have also been accomplished using mixed-phase extraction membranes with both re-versed-phase and cation-exchange properties (294,295), or solid-phase extraction columns packed with cation-exchange materials such as CM-Sephadex C-25 (301), aromatic sulfonic acid (310), and carboxylic acid (283, 300). For the same purpose, metal chelate affinity chromatography has also been employed. In this technique, the tetracyclines are specifically absorbed on the column sorbent by chelation with copper ions bound to small chelating Sepharose fast flow column (278-281, 294-296). 

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