The following reactions could not be explained by open chain structure of D-glucose:
1. The pentaacetate of glucose does not react with hydroxylamine indicating the absence of free -CHO group.
2. Despite having aldehyde group glucose does not form hydrogen sulphite addition product with sodium hydrogen sulphite and glucose does not give Schiff's test.
3. Glucose exists in two different crystalline form which are known as α-D-glucose and β-D- glucose
