Non-enzymic Acylation, Deacylation and Migration

1 Non-enzymic Acylation, Deacylation and Migration. Traditionally, acetylation of a reducing sugar with acetic anhydride and fused sodium acetate gives predominantly the fully acetylated equatorial (usually p) pyranose, because of the greater acidity and nucleophilicity of the equatorial OH, whereas acid-catalysed acetylation gives the axial acetate, thermodynamically favoured by the anomeric elfect. 

Cellulose acetate is a major commodity chemical. It is made by acid-catalysed acetylation of cellulose with acetic anhydride, often after the cellulose has been acid-swollen and sometimes partly hydrolysed to reduce the DP [the acid catalyst is often the (cheap) sulfuric acid]. Material with DS 2.2-2.3 is used for lacquers and plastics the acetone-soluble material of slightly higher DS (2.3-2.4) is spun into acetate rayon and cellulose acetate of DS 2.5-2.6 is used for photographic film. In this application it has replaced nitrocellulose by 

Cellulose propionate and butyrate, and mixed esters, are made similarly and have uses dictated by their greater solubility in cheap organic solvents such as toluene. 

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