Which of the following statements is true regarding a carbohydrate having five carbon atoms and an aldehyde group ?

Options

A. It can have 8 stereo iosmers
B. It can have 4 stereo isomers
C. It can have 2 stereo isomer
D. All the above

Answer

To determine which statement is true regarding a carbohydrate that has five carbon atoms and an aldehyde group, we will analyze the structure and properties of such a carbohydrate step by step.

### Step 1: Identify the Structure of the Carbohydrate
A carbohydrate with five carbon atoms and an aldehyde group is classified as an aldopentose. The general structure can be represented as follows:
- The aldehyde group (–CHO) is located at one end of the carbon chain.
- The remaining four carbon atoms will each have hydroxyl (–OH) groups attached.

### Step 2: Draw the Structure
The structure of an aldopentose can be drawn as:
```
CHO
|
C1 - OH
|
C2 - OH
|
C3 - OH
|
C4 - CH2OH
```
Here, C1 is the carbon with the aldehyde group, and C2, C3, and C4 are the other carbons with hydroxyl groups.

### Step 3: Identify Chiral Centers
A chiral center (or chiral carbon) is a carbon atom that is bonded to four different groups. In our structure:
- C1 is not chiral because it has the same hydrogen atoms.
- C2 has four different groups (–OH, –H, –CHO, and the carbon chain), so it is chiral.
- C3 also has four different groups (–OH, –H, –CH2OH, and the carbon chain), so it is chiral.
- C4 has four different groups (–OH, –H, –CH2OH, and the carbon chain), so it is chiral.

Thus, there are **3 chiral centers** in this aldopentose.

### Step 4: Calculate the Number of Stereoisomers
The number of stereoisomers can be calculated using the formula:
\[ \text{Number of stereoisomers} = 2^n \]
where \( n \) is the number of chiral centers.

In our case, since we have 3 chiral centers:
\[ \text{Number of stereoisomers} = 2^3 = 8 \]

### Conclusion
The true statement regarding a carbohydrate having five carbon atoms and an aldehyde group is that it has **8 stereoisomers**.

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