Which of the following is not an isomer of but-1-yne ?

Options

A. But-2-yne
B. But-2-ene
C. Buta-1, 3- diene
D. Methyl cyclopropene

Answer

To determine which of the following compounds is not an isomer of but-1-yne, we first need to understand what but-1-yne is and what isomers are.

### Step 1: Identify the structure and formula of but-1-yne.
But-1-yne is an alkyne with the following structure:
- **Chemical formula**: C4H6
- **Structural formula**: CH3C≡CCH3

### Step 2: Understand the concept of isomers.
Isomers are compounds that have the same molecular formula but different structural formulas. Therefore, we need to find compounds that also have the formula C4H6.

### Step 3: List possible isomers of but-1-yne.
1. **But-1-yne (C4H6)**: CH3C≡CCH3
2. **But-2-yne (C4H6)**: CH3C≡CCH (where the triple bond is between the second and third carbon).
3. **1,3-butadiene (C4H6)**: CH2=CH-CH=CH2 (a diene with two double bonds).
4. **Cyclobutene (C4H6)**: A cyclic compound with one double bond.

### Step 4: Identify the compound that is not an isomer.
Now, we need to check the options provided (not listed in the question, but inferred from the transcript):
- If one of the options is **butane (C4H10)**, it is not an isomer of but-1-yne because it has a different molecular formula (C4H10).

### Conclusion:
The compound that is not an isomer of but-1-yne is butane (C4H10).