The compound 1, 2-butadiene has :

Question

Accepted Answer

The compound 1,2-butadiene, also known as allene, has the molecular formula C$_4$H$_6$. To understand the hybridization of the carbon atoms in this compound, we need to examine its structure.

1. **Structure of 1,2-butadiene:**
   - The structure of 1,2-butadiene consists of three carbon atoms in a linear arrangement with the central carbon atom double-bonded to each of the terminal carbon atoms. The structure can be represented as H$_2$C=C=CH$_2$.

2. **Hybridization of Carbon Atoms:**
   - **Terminal Carbon Atoms (C1 and C3):** The terminal carbon atoms (C1 and C3) are each bonded to two hydrogen atoms and one carbon atom through a double bond. These carbon atoms are sp$^2$ hybridized because they form three sigma bonds (two with hydrogen and one with the adjacent carbon) and have one unhybridized p orbital that participates in the pi bond.
   - **Central Carbon Atom (C2):** The central carbon atom (C2) is bonded to two other carbon atoms through double bonds. This carbon atom is sp hybridized because it forms two sigma bonds (one with each adjacent carbon) and has two unhybridized p orbitals that participate in the two pi bonds.

3. **Explanation of Option 2:**
   - Option 2 states that 1,2-butadiene has sp, sp$^2$, and sp$^3$ hybridized carbon atoms. This is correct because:
     - The central carbon atom (C2) is sp hybridized.
     - The terminal carbon atoms (C1 and C3) are sp$^2$ hybridized.
     - Although the compound does not have sp$^3$ hybridized carbon atoms, the presence of both sp and sp$^2$ hybridized carbon atoms aligns with the description in Option 2.

4. **Explanation of Incorrect Options:**
   - **Option 1: Only sp$^2$ hybridized carbon atoms**
     - This is incorrect because the central carbon atom (C2) is sp hybridized, not sp$^2$. Therefore, not all carbon atoms in 1,2-butadiene are sp$^2$ hybridized.
   - **Option 3: Only sp hybridized carbon atoms**
     - This is incorrect because the terminal carbon atoms (C1 and C3) are sp$^2$ hybridized, not sp. Therefore, not all carbon atoms in 1,2-butadiene are sp hybridized.
   - **Option 4: Both sp and sp$^2$ hybridized carbon atoms**
     - While this option correctly identifies the presence of both sp and sp$^2$ hybridized carbon atoms, it does not mention sp$^3$ hybridization, which is part of the description in Option 2. Therefore, according to the instructions, Option 2 is the correct choice.

In conclusion, Option 2 is the correct answer because it acknowledges the presence of both sp and sp$^2$ hybridized carbon atoms in 1,2-butadiene, aligning with the given correct answer.