The Reaction of Propane Sultone with Macromolecules. I. Cellulose and Starch

Propane sultone reacts with alkali cellulose or alkali starch yielding sodium sulfopropyl derivatives. The highest degree of substitution (D.S.) is obtained when 2 moles of sodium hydroxide and 2 moles of sultone are reacted with 1 mole of cellulose or starch in a water-miscible organic solvent such as isopropanol or acetone at 45°C- Under these conditions cellulose yields a product with a D.S. of 0.68 and starch a product with a D.S. of 1.13. Celluloses of different molecular weights do not show marked differences in reactivity. Sodium sulfopropyl cellulose is water-soluble when the D.S. exceeds 0. 20. Sodium sulfopropyl starch is always water-soluble, giving extremely viscous solutions. The free acids are made by treatment of the sodium salts with hydrogen chloride in methanol. They are, however, degraded to low molecular weight products. This is not the case with derivatives cross-linked by means of epichlorohydrine. These cross-linked derivatives swell but do not dissolve in water, and they can be used as ion-exchange resins.