Quantitative Determination of Free Hydroxyl Groups
The simplest procedure for the quantitative measurement of the number of free hydroxyl groups on a partially substituted polysaccharide molecule employs acetylation and measures the excess of acetic anhydride added to the unknown sample. The presence of perchloric acid catalyzes the reaction and leads to quantitative acetylation of the free hydroxyls in the investigated material at room temperature. After the esterification of the hydroxyl groups has been accomplished, the unused acetic anhydride will be hydrolyzed by adding water to the reaction mixture. The amount of unused acetic acid is determined by titration with standard base solution. The reaction takes place as follows: Open image in new window The procedure described here is based on the publication of Fritz and Schenk (1959). A micromodification has been described by Schenk and Santiago (1962).
KeywordsAcetic Anhydride Hydroxamic Acid Acid Anhydride Pyromellitic Dianhydride High Molecular Weight Polysaccharide
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