Glucose exists in two crystalline forms and which are anomers of each other.

Glucose does not react with Schiff's reagent because after the internal cyclisation, it forms either anomer or -anomer. In these forms, free aldehydic group is not present.

Glucose forms open chain structure in aqueous solution which contains aldehyde at chain end. This aldehydic group reacts with to form oxime. On the other hand, glucose penta acetate being a cyclic structure even in aqueous form does not have terminal carbonyl group. Therefore it will not react with .

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