Question

An aqueous solution of glucose behaves as an aldehyde because ________.

Answer 1

An aqueous solution of glucose behaves as an aldehyde because it's cyclic hemiacetal, the predominant form, is in equilibrium with the free aldehyde form.
Glucose is one of the sixteen aldohexose stereoisomers. Glucose has carbonyl and hydroxyl group, so glucose in aquatic solution form hemiacetal.

Answer 2

because It's cyclic hemiacetal and the predominant form is in equilibrium with the free aldehyde form. as glucose has an aldehyde group and five hydroxyl group and can form an intramolecular cyclic hemiacetal. In aqueous solution, glucose exists in open and closed forms.when the process of converting the close form to open form and them back to the close form the rotate of the c1 and c 2 happened, that rotation produces the two anomers α & β. So the equilibrium of α & β in solution is a resulting of this mutarotation. In glucose, the anomer β is more predominate than α anomer.