Which of the following compounds is D-aldopentose?

Options

A.
B.
C.
D.

Answer

To determine which of the given compounds is a D-aldopentose, we can follow these steps:

### Step 1: Understand the Definition of D-Aldopentose
- An aldopentose is a monosaccharide (sugar) that contains five carbon atoms and an aldehyde group (–CHO) at one end. The "D" designation indicates the configuration of the molecule based on the orientation of the hydroxyl (–OH) group on the last chiral carbon.

### Step 2: Identify the Structure of Aldopentose
- Aldopentoses have the general formula C5H10O5. They contain five carbon atoms, one of which is part of the aldehyde group. The structure can be represented as follows:
- C1: Aldehyde group (–CHO)
- C2 to C5: Hydroxyl groups (–OH) attached to the carbon chain.

### Step 3: Check for Chiral Carbons
- Aldopentoses will have chiral centers. For a D-aldopentose, the last chiral carbon (C4 in a linear structure) must have the hydroxyl group (–OH) on the right side when the molecule is drawn in a Fischer projection.

### Step 4: Analyze the Given Compounds
- Examine each compound provided in the question:
1. Count the number of carbon atoms (should be 5).
2. Check for the presence of the aldehyde group at C1.
3. Determine the configuration of the last chiral carbon (C4) to see if the –OH group is on the right side.

### Step 5: Identify the Correct Compound
- After analyzing each compound based on the criteria above, identify which one meets all the requirements of a D-aldopentose.

### Conclusion
- The compound that has five carbons, an aldehyde group at C1, and the –OH group on the right side of the last chiral carbon is the correct D-aldopentose.