Sulfate groups, saponification

The complete hydrolysis of the soluble cellulose derivative required gradual addition of water and, preferably, acid. Water can act on cellulose acetate hydrogensulfate in three ways (a) saponification of sulfate groups, (b) saponification of acetate groups, and (c) hydrolysis of glycosidic bonds. Reaction (a) is most rapid and occurs under the mildest conditions. As Table II shows, the product is not any more water soluble (Entries 1-4). Under more severe conditions, the deacetylation (b) has proceeded to water-soluble products, the total amount of dissolved carbohydrates corresponding to theory (Entries 5-10). How-... 

In both cases of catalytic polymerisation, the chain breaks in the absence of activity, i.e. when the end groups lose the ability to bond with cyclic molecules. This can be due to the detachment of the end groups, either by the water saponification of sulfate groups (for cationic polymerisation) or by the thermolysis of tetramethylammonia groups (for anionic polymerisation). 

The saponification step is accompanied by the disappearance of the photoline of the C=0 carbon of the acetate group at a binding energy of 282.2 eV in the XPS spectrum. In addition, in the IR-ATR spectrum a broad OH stretching vibration band appears at 3410 cm (Fig. 23). According to Clark and Briggs, on subsequent SO2 plasma treatment, sulfate groups are formed [124,125]. SO functions may be incorporated into the poly(vinyl chloride) sequences as well. 

In carbohydrate trityl ethers and the partially acylated carbohydrate derivatives obtained from them, the free hydroxyl groups may be etheri-fied with other alcohols. This method has been used repeatedly, particularly for the preparation of partially methylated compounds. With the alkali resistant trityl ethers, any alkaline alkylation method may be used, for example, dimethyl sulfate and alkali, or methyl iodide and silver oxide. In choosing an alkylation method for partially acylated compounds, one must be selected which does not cause acyl migration or saponification. 

Similarly, desulfation should lead to a decrease in the acidic properties and the appearance of more hydroxyl groups. If the new hydroxyl groups are in the correct position, an enhanced periodic acid - Schiff reaction may result. Although sulfation methods have been applied to histochemical studies with the resulting induction of metachromasia (73) and basophilia 74)i attempts at desulfation by saponification have not been satisfactory (75), probably because of anhydro ring formation. 

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