Toluene sulphonation

A) Toluene -sulphonates. For directions, using an acetone solution of toluene-/) Sulphonyl chloride, see p. 249 use o 3-o 5 g. of the phenol. Note that the chloride should be dissolved in a minimum of acetone, otherwise separation of the ester may be slow and incomplete. 

Some less reactive tertiary amines can be mixed with an excess of methyl toluene-/)-sulphonate, m.p. 28 , and the mixture (without a solvent) heated to a much higher temperature. The mixture is allowed to cool, but before solidification occurs, it is thoroughly stirred with ether to extract unused sulphonate, and the insoluble quaternary metho-toluene-/)-sulphonate may then crystallise. If ciystallisation does not occur, dissolve this residue in ethanol and treat one portion with ethanolic picric acid (to precipitate the methopicrate) and another portion with cold concentrated ethanolic sodium iodide (to precipitate the methiodide). (M.ps. of the siilphon.ates, pp. 553 -554.)... 

Dinltro-benzoate Phenyl-ureldo Acid p-Toluene- sulphonate 2 4-Dlchloro-phenoxy-acetate a-Napbthyl-ureldo Acid Phthalyl Derivative... 

The sulphonation of toluene at 100-120° results in the formation of p-toluene-sulphonic acid as the chief product, accompanied by small amounts of the ortho and meta isomers these are easily removed by crystallisation in the presence of sodium chloride. Sulphonation of naphthalene at about 160° 3uelds largely the p-sulphonic acid at lower temperatures (0-60°) the a-siil-phonic acid is produced almost exclusively. 

Amins B.P. M.P. Methlodids PIcrate Methyl p-toluene- sulphonate Other Derivatives... 

No cresol is obtained if sodium hydroxide alone is used, presumably because the fused sodium hydroxide has no solvent action upon the sodium p-toluene-sulphonate. Potassium hydroxide alone gives excellent results, as do also mixtures of Sodium and potassium hydroxide containing not less than 28 per cent, of potassium hydroxide. The experimental details utilise the minimum amount of potassium hydroxide for the salce of economy. 

A number of basic materials such as hydroxides, hydrides and amides of alkaline and alkaline earth metals and metal oxides such as zinc oxide and antimony oxide are useful catalysts for the reaction. Acid ester-exchange catalysts such as boric acid, p-toluene sulphonic acid and zinc chloride are less... 

Toluene-2,6-di isocyanate p-Toluene sulphonic acid o-Toluidine... 

The effect of the catalyst-steroid ratio has been studied for the p-toluene-sulphonic acid-catalyzed ketalization of androst-4-ene-3,17-dione. Selective formation of the 3-monoketal is observed with the use of an equimolar amount of ethylene glycol and a low ratio of catalyst to steroid. ... 

Oxidation of malonic acid by Cr(VI) has been noted briefly by Snethlage and later by Kemp and Waters . The kinetics are simple second-order but the acidity dependence is complex. Heckner et a/. find the alkaline permanganate oxidation of malonic acid (and also of o- and p-toluic acids and of p-toluene-sulphonic acid) to be retarded by added Mn(VI), viz. 

The catalyst anion has also been shown to have a large influence on the reaction rate. The extraction constant of tetra-n-butylammonium salts between water and chloroform decreases with different anions as follows picrate CIO4 > T > toluene sulphonate > NO.-i > Br > benzoate > Cf > acetate > OH (Esikova, 1997 Dehmlow, 1993). 

The availability of Nafion on silica has not only lowered the cost of the resin but also has made it versatile (Sun et al., 1997 Harmer et al., 1998). A number of industrially important reactions have been attempted, with considerable success, with these catalysts. Consider the Fries rearrangement of phenyl acetate to p-acetyl phenol (/t-hydroxy acetophenone). This has been accomplished by Hoelderich and co-workers (Heidekum, 1998). In the ca.se of alkylation of benzene with benzyl alcohol, Amberlyst-15 and p-toluene sulphonic acid are ineffective and Nafion on silica works well at 80 °C. 

Gonzalez and Holt (1981) have shown how macrocyclic lactones can be made conveniently in microemulsion media. Thus, intramolecular e.sterification of (o-hydroxy alkanoic acids can be carried out with a very small amount of acid catalysts like p-toluene sulphonic acid, and rates are markedly higher as compared to simple media. 

A trade-off between selectivity and solvability should be considered when selecting a solvent. Adding co-solvents can make tough separations technically and economically feasible. Lee and Gentry (1997) have tabulated dielectric constants of selected solvents. A new class of solvents is based on the use of an aqueous. solution of hydrotropes. Gaikar and Sharma (1989) have reported the separation of close-boiling p-cresol and 2,6-xylenol with aqueous solutions of hydrotropes, such as the sodium salt of p-toluene sulphonic acid, as a novel solvent in extractive distillation. 

Polymeric adsorbents have also been found to be very useful, and even highly water-loving undesired materials like p-toluene sulphonic acid from waste streams can be recovered via ad.sorption and regeneration with solvents like fv -propanol. In such instances, the regeneration of activated carbons is not satisfactory, even with aqueous sodium hydroxide. Solutes like phenols, substituted phenols, aromatic amines, heterocyclic amines (pyridine, picolines, etc.) can be recovered, in a rewarding way, from aqueous solutions. 

An example of dimerization of the intermediates of an electrode reaction is provided by the reduction of acrylonitrile in a sufficiently concentrated aqueous solution of tetraethylammonium p-toluene sulphonate at a mercury or lead electrode. The intermediate in the reaction is probably the dianion... 

---