Ether-chlorosulfonic acid complexes

The most common way to modify aromatic polymers for application as a PEM is to employ electrophilic aromatic sulfonation. Aromatic polymers are easily sulfonated using concentrated sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, or sulfur trioxide (or complexs thereof). Postmodification reactions are usually restricted due to their lack of precise control over the degree and location of functionalization, the possibility of side reactions, or degradation of the polymer backbone. Regardless, this area of PEM synthesis has received much attention and may be the source of emerging products such as sulfonated Victrex poly (ether ether ketone). 

In order to prepare advanced molecules of poly(arylene ether sulfones) for fuel cell apphcations without sacrificing their excellent physical properties, Noshay and Robeson developed a mild sulfonation procedure for the commercially available bisphenol-A-based poly(ether sulfone) [62,63]. The sulfonation agents that have been used for this polymer modification are chlorosulfonic acid and a sulfur trioxide-triethyl phosphate complex. Recently, Kerres and co-workers [102] reported an alternative sulfonation process of commercial polysulfone based on a series of steps, including metalation-sulfmation-oxidation reactions. 

The final isolated product, after the aqueous work-up procedure, was 2-hydroxypropanesulfonic acid 10. Many industrial studies used chlorosulfonic acid in diethyl ether the complex is prepared by dropwise addition of chlorosulfonic acid to diethyl ether at 0 °C. Under these conditions, the initial product of the reaction of propene 8 with chlorosulfonic acid in diethyl ether is probably the chlorinated sulfonic acid 11. The chlorine atom in this compound is very reactive and consequently the isolated products are generally the alkenesul-fonic acid 12 or the hydroxysulfonic acid 10 (Scheme 2) ... 

The chlorosulfonic acid-ether complex is a milder reagent than free chlorosulfonic acid for the sulfation of alcohols and is outstanding in respect of yield and purity of the alkyl hydrogen sulfates 45 produced. The use of chlorosulfonic acid in diethyl ether at low temperature (-50 °C) is a standard method for sulfation of higher (Cg-C28) primary and secondary alcohols. The latter have also been successfully sulfated using a mixture of chlorosulfonic acid in acetic acid the active entity here is probably acetyl sulfate. This method has been adapted for the synthesis of very pure sodium alkyl sulfates for use as detergents thus chlorosulfonic acid and 1-dodecanol were successively added to acetic acid at low temperature (—10 to -15 °C), the solid product was neutralized with sodium carbonate and unreacted alcohols extracted with solvents to give 98.6% pure dodecanyl sodium sulfate. ... 

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