Question

why is glucose pentahydroxy aldehyde??​

Answer 1

Answer:

Glucose is a pentahydroxy aldehyde. ... In fact, glucose exists mainly (> 99.9 percent) in the glucopyranose form, a cyclic hemiacetal. Even though the amount of aldehyde present at equilibrium is small, many reactions of glucose and similar sugars are those of the free aldehyde group.

Explanation:

Answer 2

Glucose is the most widely distributed carbohydrate. It is also called dextrose because it is dextrorotatory, meaning that it rotates the plane of plane-polarized light in the (+) direction. It has molecular formula C6H12O6 and is structurally a pentahydroxy aldehyde. It shows chemical properties of the carbonyl as well as the hydroxyl groups. It differs importantly from most simple aldehydes, however, because it forms stable hemiacetals, making use of one of its own hydroxyl groups as the alcohol. In fact, the cyclic hemiacetal form of glucose is more stable than the open-chain carbonyl form, and a sample of crystalline glucose will not, for example, show an infrared absorption band in the carbonyl region. In this way it differs from a typical aldehyde, whose hemiacetal form is usually too unstable to be isolated. Nevertheless, when glucose is placed in solution an equilibrium is established between the hemiacetal and free aldehyde forms.