Total number of isomers, considering only structural isomers of cyclic ethers with the molecular formula `C_(4)H_(8)O` is…………...

Explanation

To determine the total number of structural isomers of cyclic ethers with the molecular formula \( C_4H_8O \), we will analyze the possible cyclic structures that can be formed with this formula.

### Step 1: Identify the types of cyclic ethers
Cyclic ethers can be formed with different ring sizes. For \( C_4H_8O \), we can consider:
- 3-membered rings (epoxides)
- 4-membered rings (oxetanes)
- 5-membered rings (furan-like structures)

### Step 2: Construct the 3-membered cyclic ether
For a 3-membered cyclic ether (epoxide), we can have:
- **1,2-epoxybutane**: This structure has two carbons in the ring and one carbon as a substituent. The oxygen is part of the ring.

### Step 3: Construct the 4-membered cyclic ether
For a 4-membered cyclic ether (oxetane), we can have:
- **Oxetane**: A four-membered ring with one oxygen atom and three carbon atoms.

We can also have:
- **Substituted oxetanes**: We can place a methyl group on one of the carbons in the ring, leading to different isomers.

### Step 4: Construct the 5-membered cyclic ether
For a 5-membered cyclic ether, we can have:
- **Tetrahydrofuran**: A five-membered ring with one oxygen atom and four carbon atoms.

We can also have:
- **Substituted tetrahydrofuran**: Similar to the oxetane, we can place a methyl group on one of the carbons in the ring.

### Step 5: Count the isomers
Now, we will summarize the isomers we have constructed:
1. **1,2-epoxybutane** (3-membered ring)
2. **Oxetane** (4-membered ring)
3. **Methyl-substituted oxetanes** (two isomers possible)
4. **Tetrahydrofuran** (5-membered ring)
5. **Methyl-substituted tetrahydrofuran** (two isomers possible)

### Total Count
- 1 (3-membered) + 1 (4-membered) + 2 (substituted oxetanes) + 1 (5-membered) + 2 (substituted tetrahydrofuran) = **6 structural isomers**.

### Final Answer
The total number of structural isomers of cyclic ethers with the molecular formula \( C_4H_8O \) is **6**.

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