Alkaline degradation, of polysaccharides

Aldoses and aldosides, cyclic acetals of, 20, 219-302 Alkaline degradation, of polysaccharides, 13, 289-329 Altrose,... 

The formation of 4,5-unsaturated uronic acid residues by enzymic or alkaline degradation of polysaccharides containing uronic acids has been the object of many investigations.214... 

The consumption of effective alkali in a kraft cook corresponds to about 150 kilogram sodium hydroxide per ton of wood. As a result of the alkaline degradation of polysaccharides, about 1.6 equivalents of acids are formed for every monosaccharide unit peeled from the chain. Of the charged alkali, 60-70% is required for the neutralization of these hydroxy acids, while the rest is consumed to neutralize uronic and acetic acids (about 10% of alkali) and degradation products of lignin (25-30% of alkali). 

As stated previously, the alkaline degradation of polysaccharides proceeds by a peeling process in which the reducing end-group is liberated from a chain by elimination of the rest of the chain asa glycoxyanion. Elimination takes place when the chain is in the position beta to a carbonyl group of the reducing end-unit. Eliminations of this type can be exemplified by the action of alkali on 4-ethoxy-2-butanone (IV) to form 3-buten-2-one (V). 

Alkaline degradation of polysaccharides usually stops before the degra-... 

ALKALINE DEGRADATION OF POLYSACCHARIDES normal route to isosaooharinates... 

The enolate ion (XXXV), formed from a carbonyl group at either C2 or C3, is the same ion that is the active participant in the alkaline degradation of polysaccharides by the -alkoxy carbonyl mechanism. Hence, it has been postulated that oxidized polysaccharides of the keto (carbonyl) type are degraded in alkali by an alkoxy-elimination reaction. The chains... 

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