The minimum number of carbon atoms an alkane should contain in order to exhibit optical activity is:

Options

A. 5
B. 6
C. 7
D. 8

Explanation

To determine the minimum number of carbon atoms an alkane should contain in order to exhibit optical activity, we need to understand the concept of chirality and asymmetric carbon atoms.

### Step-by-Step Solution:

1. **Understanding Optical Activity**:
- Optical activity in organic compounds arises when a molecule has a chiral center, which is typically a carbon atom bonded to four different groups. This carbon atom is referred to as an asymmetric carbon.

2. **Identifying Asymmetric Carbon**:
- For a carbon atom to be asymmetric, it must be bonded to four different substituents. This means that if we want to create an optically active alkane, we need to ensure that at least one of the carbon atoms in the molecule has four distinct groups attached.

3. **Constructing an Alkane**:
- Let's consider the simplest alkane structure that can potentially have an asymmetric carbon. Starting with a straight-chain alkane, we can analyze the structure of alkanes with increasing carbon counts.

4. **Minimum Carbon Count**:
- For an alkane to have an asymmetric carbon, we can start with a 7-carbon alkane (heptane).
- In heptane, we can create a branched structure (for example, 2-methylhexane) where one of the carbon atoms is bonded to four different groups:
- One hydrogen atom
- One methyl group (−CH3)
- One ethyl group (−C2H5)
- One propyl group (−C3H7)

5. **Counting the Carbons**:
- In the branched structure, we have:
- 1 carbon from the methyl group
- 2 carbons from the ethyl group
- 3 carbons from the propyl group
- 1 carbon from the asymmetric carbon itself
- This gives us a total of 7 carbon atoms.

6. **Conclusion**:
- Therefore, the minimum number of carbon atoms an alkane should contain in order to exhibit optical activity is **7**.

### Final Answer:
The minimum number of carbon atoms an alkane should contain in order to exhibit optical activity is **7**.