Total number of structural isomers of `C_9H_18` containing cyclohexane ring.

Explanation

To determine the total number of structural isomers of C₉H₁₈ that contain a cyclohexane ring, we can follow these steps:

### Step 1: Understand the structure
Cyclohexane (C₆H₁₂) is a six-membered carbon ring. To form C₉H₁₈, we need to add three more carbon atoms to the cyclohexane structure.

### Step 2: Identify the possible structures
We can add the three additional carbon atoms in various ways:
1. As a straight chain (propyl group).
2. As two methyl groups (dimethyl).
3. As an ethyl group and a methyl group.

### Step 3: Draw the isomers
1. **Cyclohexane with a propyl group**:
- Attach a propyl group to any carbon of the cyclohexane.

2. **Cyclohexane with two methyl groups**:
- Attach two methyl groups to different carbons of the cyclohexane.
- Consider the positions of the methyl groups (1,2-dimethyl, 1,3-dimethyl, etc.).

3. **Cyclohexane with an ethyl and a methyl group**:
- Attach an ethyl group and a methyl group to different carbons of the cyclohexane.

### Step 4: Count the isomers
By systematically drawing each possible structure and ensuring that you account for different positions of the substituents, you can count the total number of unique structural isomers.

### Final Count
After drawing and counting all the unique combinations, we find that the total number of structural isomers of C₉H₁₈ containing a cyclohexane ring is **12**.

### Summary
The total number of structural isomers of C₉H₁₈ that contain a cyclohexane ring is **12**.

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