Number of acidic hydrogen atoms in but-1-yne is

Options

A. 1
B. 2
C. 3
D. 4

Answer

To determine the number of acidic hydrogen atoms in but-1-yne, we can follow these steps:

### Step 1: Understand the structure of but-1-yne
But-1-yne is an alkyne with the molecular formula C4H6. Its structure can be represented as:
\[ \text{CH}_3\text{CH}_2\text{C} \equiv \text{CH} \]
This shows that but-1-yne has a triple bond between the last two carbon atoms.

### Step 2: Identify the hydrogen atoms in but-1-yne
In the structure:
- The first carbon (C1) has 3 hydrogen atoms (CH3).
- The second carbon (C2) has 2 hydrogen atoms (CH2).
- The third carbon (C3) is part of the triple bond and has no hydrogen atoms.
- The fourth carbon (C4) has 1 hydrogen atom (C≡CH).

### Step 3: Determine which hydrogen atoms are acidic
In alkynes, the hydrogen atom attached to the terminal carbon (the carbon at the end of the chain with the triple bond) is considered acidic. This is because it can be easily removed by a base, forming a carbanion.

In but-1-yne, the only terminal hydrogen is the one attached to C4 (the one in C≡CH). This hydrogen is acidic.

### Step 4: Count the number of acidic hydrogen atoms
From the analysis, we find that there is only **1 acidic hydrogen atom** in but-1-yne.

### Conclusion
Thus, the number of acidic hydrogen atoms in but-1-yne is **1**.