The chain isomer of pent-1-yne is ...........

Answer

To find the chain isomer of pent-1-yne, we need to follow these steps:

### Step 1: Understand the structure of pent-1-yne
Pent-1-yne is an alkyne with a triple bond between the first and second carbon atoms. Its structural formula can be represented as:
\[ \text{CH}_3-\text{CH}_2-\text{C} \equiv \text{C}-\text{H} \]

### Step 2: Identify the molecular formula
The molecular formula of pent-1-yne is \( \text{C}_5\text{H}_8 \). This indicates that there are 5 carbon atoms and 8 hydrogen atoms in the molecule.

### Step 3: Determine the chain isomers
Chain isomers differ in the branching of the carbon chain. For pent-1-yne, we can create a branched structure by moving the position of the triple bond and rearranging the carbon atoms.

### Step 4: Draw the chain isomer
One possible chain isomer of pent-1-yne is 3-methylbut-1-yne. In this structure:
- The main chain consists of 4 carbon atoms (but-).
- A methyl group (CH₃) is attached to the third carbon of the main chain.
- The triple bond is still present at the first carbon.

The structural formula for 3-methylbut-1-yne can be represented as:
\[ \text{CH}_3-\text{C} \equiv \text{C}-\text{CH}_2-\text{CH}_3 \]

### Step 5: Name the chain isomer
The name of this isomer is 3-methylbut-1-yne. The numbering is done to give the lowest possible numbers to the triple bond.

### Conclusion
The chain isomer of pent-1-yne is **3-methylbut-1-yne**.

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