Sulphonates aromatic, reactions

The benzene nucleus in polystyrene undergoes normal aromatic reactions and thus the polymer may be, for example, alkylated, halogenated, nitrated and sulphonated. A frequent practical difficulty in carrying out such reactions is one of finding a reaction medium in which the polymer is soluble also, chain scission, cross-linking and discoloration often accompany these reactions. Chemically-modified polystyrenes have found little commercial application but sulphonated styrene-divinylbenzene copolymers (which are cross-linked) find use as cationic exchange resins the nature of such resins is illustrated by the following strueture ... 

Reaction at Sulphur.—The oxidation of benzo[6]thiophens to sulphoxides by t-butyl hypochlorite has been studied. In the presence of a ruthenium catalyst, dibenzothiophen was oxidized by oxygen to the sulphone. The reactions of benzo[ >]thiophen 1,1-dioxides with various reagents such as amines, amino-alcohols,3-aminopropylsilanes, and aromatic sulphonyl chlorides have been studied. Four detailed papers on the reaction of dibenzophenonium salts with aryl-lithiums have appeared in which the mechanism of ligand exchange was elucidated. " ... 

Aromatic nitriles (or aryl cyanides) can be obtained by methods (1) and (3). but not by method (2). In addition, aromatic nitriles can be prepared by two other methods, (a) from the corresponding diazo compound by Sandmeyer s Reaction (p. 189), (b) by fusing the corresponding sulphonic acid (or its salts)... 

A further difference between aliphatic and aromatic hydrocarbons is that only the latter are capable of direct sulphonation. Thus benzene when heated with concentrated sulphuric acid gives benzenesulphonic acid, a reaction which proceeds more readily, however, if chlorosulphonic acid is used instead of sulphuric acid an excess of chlorosulphonic acid however may convert the sul phonic acid into the sulphonyl chloride (c/. p. 181). 

SULPHONATION OF AROMATIC HYDROCARBONS Aromatic hydrocarbons may be mono-sulphonated by heating with a slight excess of concentrated sulphuric acid for benzene, oleum (7-8 per cent. SOj) gives somewhat better results. The reaction is usually complete when all the hydrocarbon has dissolved. Examples are ... 

SULPHONATION OF AROMATIC AMINES If aniline is treated with excess of concentrated sulphuric acid and the resulting mixture, which contains aniline sulphate, is heated at 180° until a test portion when mixed with sodium hydroxide solution no longer liberates aniline, p-aminobenzenesulphonic acid or sulphanilic acid is formed this separates as the dihydrate upon pouring the cooled mixture into water. The reaction prohahly proceeds as follows ... 

The imides, primaiy and secondary nitro compounds, oximes and sulphon amides of Solubility Group III are weakly acidic nitrogen compounds they cannot be titrated satisfactorily with a standard alkaU nor do they exhibit the reactions characteristic of phenols. The neutral nitrogen compounds of Solubility Group VII include tertiary nitro compounds amides (simple and substituted) derivatives of aldehydes and ketones (hydrazones, semlcarb-azones, ete.) nitriles nitroso, azo, hydrazo and other Intermediate reduction products of aromatic nitro compounds. All the above nitrogen compounds, and also the sulphonamides of Solubility Group VII, respond, with few exceptions, to the same classification reactions (reduction and hydrolysis) and hence will be considered together. 

The operation of the nitronium ion in these media was later proved conclusively. "- The rates of nitration of 2-phenylethanesulphonate anion ([Aromatic] < c. 0-5 mol l i), toluene-(U-sulphonate anion, p-nitrophenol, A(-methyl-2,4-dinitroaniline and A(-methyl-iV,2,4-trinitro-aniline in aqueous solutions of nitric acid depend on the first power of the concentration of the aromatic. The dependence on acidity of the rate of 0-exchange between nitric acid and water was measured, " and formal first-order rate constants for oxygen exchange were defined by dividing the rates of exchange by the concentration of water. Comparison of these constants with the corresponding results for the reactions of the aromatic compounds yielded the scale of relative reactivities sho-wn in table 2.1. 

When the concentration of 2-phenylethanesulphonate anion was >0-5 mol 1, or when 2-mesitylethanesulphonate anion (v), " mesitylene-a-sulphonate anion, or iso-durene-a -sulphonate anion were nitrated, the initial part of the reaction deviated from a first-order dependence on the concentration of the aromatic towards a zeroth-order dependence. 

A consequence of the reaction is that it is possible to produce a range of polymers by reacting bisphenates with appropriately activated aromatic dihalides. In the case when the dihalide is activated by the presence of a sulphone —SO,— group the polymers may be referred to as polysulphones. The Amoco materials are prepared in this way. 

Conant and Peterson123 made the first kinetic study of the coupling of diazonium ions with aromatics, and measured the rates of reaction of diazotised aniline and its 2-MeO, 4-Me, 4-Br and 4-S03H derivatives with the sodium salts of 4-hydroxybenzenesulphonic acid, 2-naphthol-3,6-disulphonic acid, 1-naphthol-3,8-disulphonic acid, and l-naphthol-4-sulphonic acid. The reaction was second-order, viz. 

Most research workers have employed an aqueous sulphuric acid solution of the aromatic, but a few have used other solvent systems and sulphonating agents. Principal among these are Hinshelwood et a/.139, who measured the rates of sulphonation of aromatics by sulphur trioxide in nitrobenzene at temperatures between 0 and 100 °C, a minimum of about 40 °C being employed for each compound. The initial reaction rate was given by... 

Hinshelwood et a/.145 measured the rates of sulphonation of a wide range of aromatics by sulphuric acid in nitrobenzene, at temperatures between 5 and 100 °C (Table 32), and in particular the effect of adding up to 0.012 M water was determined. The reaction followed the complex rate law... 

Eaborn and Taylor147 measured first-order rate coefficients for sulphonation of some aromatics in mixtures of trifluoroacctic acid-aqueous sulphuric acid, as sulphonation proved to be a troublesome side reaction accompanying hydrogen exchange in these media. They introduced a technique which has been found useful by later workers and makes use of the high solubility of sulphonic acids in... 

The first kinetic study appears to have been that of Martinsen148, who found that the sulphonation of 4-nitrotoluene in 99.4-100.54 wt. % sulphuric acid was first-order in aromatic and apparently zeroth-order in sulphur trioxide, the rate being very susceptible to the water concentration. By contrast, Ioffe149 considered the reaction to be first-order in both aromatic and sulphur trioxide, but the experimental data of both workers was inconclusive. The first-order dependence upon aromatic concentration was confirmed by Pinnow150, who determined the equilibrium concentrations of quinol and quinolsulphonic acid after reacting mixtures of these with 40-70 wt. % sulphuric acid at temperatures between 50 and 100 °C the first-order rate coefficients for sulphonation and desulphonation are given in Tables 34 and 35. The logarithms of the rate coefficients for sulphonation... 

Brand et al.15B made extensive measurements of the rates of sulphonation of a range of unreactive aromatics by oleum containing up to 41 % of sulphur trioxide at temperatures between 0 and 45 °C, and found the reaction to be first-order in aromatic. First-order rate coefficients at 25 °C are given in Table 37, some of the... 

Derbyshire and Waters192 measured the rates of bromination of sodium toluene-m-sulphonate (in water) and of benzoic acid (in aqueous acetic acid) by hypobromous acid with sulphuric or perchloric acids as catalysts, all at 21.5 °C. No bromination occurred in the absence of mineral acid and the reaction was strictly first-order in aromatic and in hypobromous acid. The function of the catalyst was considered to be the formation of a positive brominating species, according to the equilibrium... 

In Volume 13 reactions of aromatic compounds, excluding homolytic processes due to attack of atoms and radicals (treated in a later volume), are covered. The first chapter on electrophilic substitution (nitration, sulphonation, halogenation, hydrogen exchange, etc.) constitutes the bulk of the text, and in the other two chapters nucleophilic substitution and rearrangement reactions are considered. 

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