Sulfonation of aromatic rings

Important reactions have included sulfur as nucleophile and leaving group in the Sn2 reaction (illustrated here see also Chapter 17), sulfonation of aromatic rings (Chapter 22), formation and reduction of thioacetals (Chapter 24) and La wesson s reagent for converting carbonyl groups to thiocarbonyl groups (Chapter 44). 

Hajipour, A.R., Miijalili, B.B.R, Zarei, A., Khazdooz, L. and Ruoho, A.E. 2004. A novel method for sulfonation of aromatic rings with siUca sulfuric acid. Tetrahedron Lett. 45(35) 6607-6609. 

The sulfonation of aromatic rings attached directly to phosphorus requires the use of oleum due to deactivation of the ring by protonated phosphorus atom. The sulfo group enters the meta-position. A certain degree of care must be taken when comparing results obtained with sulfonated ligands from different sources, as the sulfonation of even the... 

Synthetic Transformations 19.3 22.6 Sulfonation and de-Sulfonation of Aromatic Rings... 

The aromatic sulfone polymers are a group of high performance plastics, many of which have relatively closely related stmctures and similar properties (see Polymers containing sulfur, polysulfones). Chemically, all are polyethersulfones, ie, they have both aryl ether (ArOAr) and aryl sulfone (ArS02Ar) linkages in the polymer backbone. The simplest polyethersulfone (5) consists of aromatic rings linked alternately by ether and sulfone groups. 

Aromatic sulfonyl chlorides can be prepared directly, by treatment of aromatic rings with chlorosulfuric acid. ° Since sulfonic acids can also be prepared by the same reagent (11-7), it is likely that they are intermediates, being converted to the halides by excess chlorosulfuric acid. The reaction has also been effected with bromo-and fluorosulfuric acids. 

The dependence of the volatile product yield with structure can be a very sensitive probe of radiation resistance and the protective effect of aromatic rings. G(H ) was observed to decrease from 5.6 to 0.038 for cyclohexane (3) and benzene (A) after gamma irradiation at ambient temperature. Since all polymers under investigation contained the sulfone moiety, G(SO ) (Table III) is an ideal probe for radiation resistance for this series. 

Another concern for polystyrene- and some aromatic-based PEMs is hydrolysis of fhe sulfonic acid group from aromatic rings as well as hydrolytic cleavage of polymer backbone under fuel cell conditions for aromafic polymers including polyimides, poly(arylene ethers), poly(ether ketones), and poly(ether sulfones). It is well known that the sulfonation of aromafic rings is a reversible process especially at low pH and at elevated temperature (Scheme 3.3). The reversibility of sulfonation, for example, is used in fhe preparafion of trinitrotoluene or picric acid. Por the simplest membrane of the class of arylsulfonic acids (i.e., benzenesulfonic acid), fhe reacfion occurs upon freatment with a stream of superheated steam at 180°C.i ... 

Permeability of aromatic polyamide membranes have been improved by modification of aromatic rings with pendant polar groups, for examples sulfonic, carboxylic, carboxamide, and sulfonamide groups, in addition to the before-mentioned methoxy group. 

The most important applications of peroxyacetic acid are the epoxi-dation [250, 251, 252, 254, 257, 258] and anti hydroxylation of double bonds [241, 252, the Dakin reaction of aldehydes [259, the Baeyer-Villiger reaction of ketones [148, 254, 258, 260, 261, 262] the oxidation of primary amines to nitroso [iJi] or nitrocompounds [253], of tertiary amines to amine oxides [i58, 263], of sulfides to sulfoxides and sulfones [264, 265], and of iodo compounds to iodoso or iodoxy compounds [266, 267] the degradation of alkynes [268] and diketones [269, 270, 271] to carboxylic acids and the oxidative opening of aromatic rings to aromatic dicarboxylic acids [256, 272, 271, 272,273, 274]. Occasionally, peroxyacetic acid is used for the dehydrogenation [275] and oxidation of aromatic compounds to quinones [249], of alcohols to ketones [276], of aldehyde acetals to carboxylic acids [277], and of lactams to imides [225,255]. The last two reactions are carried out in the presence of manganese salts. The oxidation of alcohols to ketones is catalyzed by chromium trioxide, and the role of peroxyacetic acid is to reoxidize the trivalent chromium [276]. 

Sodium hypochlorite is used for the epoxidation of double bonds [659, 691] for the oxidation of primary alcohols to aldehydes [692], of secondary alcohols to ketones [693], and of primary amines to carbonyl compounds [692] for the conversion of benzylic halides into acids or ketones [690] for the oxidation of aromatic rings to quinones [694] and of sulfides to sulfones [695] and, especially, for the degradation of methyl ketones to carboxylic acids with one less carbon atom [655, 696, 697, 695, 699] and of a-amino acids to aldehydes with one less carbon [700]. Sodium hypochlorite is also used for the reoxidation of low-valence ruthenium compounds to ruthenium tetroxide in oxidations by ruthenium trichloride [701]. 

Poly(ether sulfones) containing aromatic rings in the backbone have much better thermal stability compared to poly(sulfur dioxide-co-alkenes). For example, PSF degrades very slowly in vacuum above 400° C, and only above 460° a more rapid decomposition begins [4], Other poly(ether sulfones) behave similarly [5]. Several reports on the thermal decomposition for poly(ether sulfones) are available in literature. A summary of such reports are given in Table 12.2.3. 

The rearrangement of arylaminosulfuric acids (arylsulfamic acids) 220 to the corresponding ring-sulfonated anilines 221 and 222 was of great interest from both mechanistic and synthetic viewpoints, because these above-named acids have been postulated as intermediates in the sulfonation of aromatic amines with sulfuric acid305 (equation 85). 

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