Determination of alkene monosulphonates and hydroxyalkane sulphonates

Alkene monosulphonates may be extracted as the sulphonic acids from strongly acid solution and determined by titration with alkali. Under these conditions the hydroxyalkane sulphonates are converted back to the sultones from which they were derived, and although these are also extracted, they are not titrated by alkali. Alternatively the alkene sulphonates in the extract may be titrated with benzethonium chloride. The hydroxyalkane sulphonates may be determined by alkaline hydrolysis followed either by measurement of the alkali consumed or by a second titration with benzethonium chloride. The following method is adapted from those of Ranky and Battaglini [20] and Martinsson and Nilsson [21]. The alkali used for hydrolysis of the sultones is alcoholic simply to prevent excessive foaming. 

Dissolve a sample containing about 1-2 g active matter in 50 ml water in a 250 ml separating funnel. 

Add 50 ml 6 M hydrochloric acid and extract with three 50 ml portions of diethyl ether (caution flammable). 

Combine the ether extracts and wash with 25 ml 3M hydrochloric acid. 

Add 50 ml ethanol and titrate to phenolphthalein with 0.1 M ethanolic sodium hydroxide. Calculate the percentage of alkene sulphonate. 

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