The first member of alkyne homologous series is

Options

A. ethyne
B. ethene
C. propyne
D. methane

Explanation

To find the first member of the alkyne homologous series, we can follow these steps:

### Step 1: Understand the General Formula
The general formula for alkynes is given as:
\[ \text{C}_n\text{H}_{2n-2} \]
where \( n \) represents the number of carbon atoms.

### Step 2: Determine the Value of n for the First Member
For the first member of the alkyne series, we set \( n = 2 \):
\[ n = 2 \]

### Step 3: Substitute n into the General Formula
Now, we substitute \( n \) into the general formula:
\[ \text{C}_2\text{H}_{2(2)-2} = \text{C}_2\text{H}_2 \]

### Step 4: Identify the Compound
The compound with the formula \( \text{C}_2\text{H}_2 \) is known as ethyne. It can also be represented structurally as:
\[ \text{C} \equiv \text{C} \]
This indicates a triple bond between the two carbon atoms.

### Step 5: Conclusion
Thus, the first member of the alkyne homologous series is ethyne.

### Final Answer
The first member of the alkyne homologous series is **ethyne (C2H2)**.

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