Number of asymmetric carbon atoms in fructose

Options

A. 2
B. 3
C. 4
D. 5

Answer

To determine the number of asymmetric carbon atoms in fructose, we can follow these steps:

### Step 1: Draw the Structure of Fructose
Fructose has the molecular formula C6H12O6. Its structure can be represented as follows:

```
CH2OH
|
H - C - OH
|
HO - C - H
|
H - C - OH
|
C = O
|
CH2OH
```

### Step 2: Identify Carbon Atoms
In the structure of fructose, we have six carbon atoms. We will label them for clarity:

1. C1
2. C2
3. C3
4. C4
5. C5
6. C6

### Step 3: Determine Asymmetry
An asymmetric carbon atom (also known as a chiral carbon) is one that has four different substituents attached to it. We will analyze each carbon atom:

- **C1**: Attached to CH2OH, H, OH, and C2. (Asymmetric)
- **C2**: Attached to H, OH, C1, and C3. (Asymmetric)
- **C3**: Attached to H, OH, C2, and C4. (Asymmetric)
- **C4**: Attached to H, OH, C3, and C5. (Asymmetric)
- **C5**: Attached to H, OH, C4, and CH2OH. (Asymmetric)
- **C6**: Attached to CH2OH, H, H, and C5. (Not asymmetric, as it has two hydrogens)

### Step 4: Count Asymmetric Carbons
From the analysis:
- C1, C2, C3, C4, and C5 are asymmetric.
- C6 is not asymmetric.

Thus, the total number of asymmetric carbon atoms in fructose is **5**.

### Final Answer
The number of asymmetric carbon atoms in fructose is **5**.

---