Glucose gives many reactions of aldehyde, because

Options

A. It is hydrolysed to acetaldehyde
B. It is polyhydroxy ketone
C. It is a cyclic aldehyde
D. It is a hemiacetal in equillibrium with its aldehyde form in solution

Explanation

To answer the question "Glucose gives many reactions of aldehyde, because...", we need to analyze the structure and properties of glucose.

### Step 1: Understand the Structure of Glucose
Glucose is a simple sugar (monosaccharide) that can exist in both linear and cyclic forms. In its linear form, glucose has an aldehyde group (-CHO) at one end of the molecule.

**Hint:** Remember that the presence of functional groups in a molecule determines its reactivity.

### Step 2: Identify the Functional Groups
In the linear form, glucose has an aldehyde group, which is responsible for its reactivity. However, glucose predominantly exists in a cyclic form (pyranose) in solution due to the reaction of the aldehyde group with one of its hydroxyl groups, forming a hemiacetal.

**Hint:** Consider how the structure of glucose changes when it forms a cyclic structure.

### Step 3: Hemiacetal Formation
When glucose cyclizes, it forms a hemiacetal. A hemiacetal is a compound formed from the reaction of an aldehyde with an alcohol. In the case of glucose, the aldehyde group reacts with a hydroxyl group on the same molecule.

**Hint:** Recall the definition of hemiacetals and how they are formed from aldehydes and alcohols.

### Step 4: Equilibrium Between Hemiacetal and Aldehyde
In solution, glucose exists in equilibrium between its cyclic hemiacetal form and its linear aldehyde form. This equilibrium allows glucose to participate in various reactions typical of aldehydes.

**Hint:** Think about how equilibrium affects the concentration of different forms of a compound in solution.

### Step 5: Conclusion
Thus, the reason glucose gives many reactions of aldehyde is that it exists as a hemiacetal in equilibrium with its aldehyde form in solution. This allows it to exhibit the reactivity characteristic of aldehydes.

**Final Answer:** Glucose gives many reactions of aldehyde because it is hemiacetal in equilibrium with its aldehyde form in solution.