Purine without ketonic group is

Options

A. Adenine
B. Adenosine
C. Cytidine
D. Thymidine

Answer

To determine which purine does not have a ketonic group, we can follow these steps:

### Step 1: Understand what purines are
Purines are a type of nitrogenous base that are essential components of nucleic acids (DNA and RNA). The two main purines are adenine and guanine.

**Hint:** Purines are characterized by their double-ring structure and are classified as nitrogenous bases.

### Step 2: Identify the ketonic group
A ketonic group is a functional group characterized by a carbon atom double-bonded to an oxygen atom (C=O) and is typically found in ketones. In the context of purines, we need to identify which of the two purines contains this group.

**Hint:** Look for the presence of a C=O bond in the structures of adenine and guanine.

### Step 3: Analyze the structures of adenine and guanine
- **Adenine**: The structure of adenine does not contain a ketonic group. It has an amine group (NH2) but lacks the C=O bond.
- **Guanine**: The structure of guanine contains a ketonic group (C=O) at one of its carbon atoms.

**Hint:** Draw or visualize the structures of both adenine and guanine to see the presence or absence of the ketonic group.

### Step 4: Conclusion
Since adenine does not have a ketonic group while guanine does, the purine without a ketonic group is **adenine**.

**Final Answer:** Adenine