Predict the number of stereoisomers in `CH_(2)OH.(CHOH)_(4).CHO`.

Options

A. 16
B. 8
C. 4
D. 2

Explanation

To determine the number of stereoisomers in the compound \( CH_2OH.(CHOH)_4.CHO \), we will follow these steps:

### Step 1: Understand the Structure
The compound can be broken down as follows:
- It has a terminal \( CH_2OH \) group.
- It has four \( CHOH \) groups in the middle.
- It ends with a terminal \( CHO \) group.

### Step 2: Draw the Structure
The structure can be visualized as:
```
CHO
|
CH
|
CH
|
CH
|
CH2OH
```
This shows the arrangement of the carbon atoms and their respective functional groups.

### Step 3: Identify Asymmetrical Carbon Atoms
An asymmetrical (or chiral) carbon atom is one that has four different groups attached to it. We will analyze each carbon atom in the structure:
1. The terminal \( CH_2OH \) does not contribute as it has two hydrogen atoms.
2. The first \( CH \) connected to \( CHO \) has different groups (CHO, CH2OH, OH, and H) → asymmetrical.
3. The second \( CH \) also has different groups (OH, CH, CH2OH, and H) → asymmetrical.
4. The third \( CH \) has different groups (OH, CH, CH2OH, and H) → asymmetrical.
5. The last \( CH \) connected to \( CH2OH \) does not contribute as it has two hydrogen atoms.

Thus, we find that there are **four asymmetrical carbon atoms** in total.

### Step 4: Apply the Stereoisomer Formula
The formula for calculating the number of stereoisomers is:
\[ \text{Number of stereoisomers} = 2^n \]
where \( n \) is the number of asymmetrical carbon atoms.

### Step 5: Calculate the Number of Stereoisomers
Since we have identified \( n = 4 \):
\[ \text{Number of stereoisomers} = 2^4 = 16 \]

### Conclusion
The total number of stereoisomers for the compound \( CH_2OH.(CHOH)_4.CHO \) is **16**.

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