Planar molecule among the following is

Options

A. `CH_(2)=CH_(2)`
B. `CH_(3)-CH_(3)`
C. `CH-=C-CH_(3)`
D. Cyclohexane

Answer

To determine which of the given molecules is planar, we will analyze the hybridization and geometry of each molecule mentioned: ethene, ethane, propine, and cyclohexene.

### Step-by-Step Solution:

1. **Identify the Structures:**
- **Ethene (C2H4)**: Contains a double bond between two carbon atoms.
- **Ethane (C2H6)**: Contains single bonds between carbon atoms.
- **Propine (C3H6)**: Contains a triple bond between the first carbon and the second carbon.
- **Cyclohexene (C6H10)**: Contains a ring structure with a double bond.

2. **Analyze Ethene:**
- Ethene has the structure: H2C=CH2.
- Each carbon in ethene is **sp² hybridized** due to the presence of a double bond.
- The geometry around each carbon is **trigonal planar**, meaning all atoms are in the same plane.
- **Conclusion**: Ethene is a planar molecule.

3. **Analyze Ethane:**
- Ethane has the structure: H3C-CH3.
- Each carbon in ethane is **sp³ hybridized**.
- The geometry around each carbon is **tetrahedral**, which means that the atoms are arranged in three dimensions.
- **Conclusion**: Ethane is not a planar molecule.

4. **Analyze Propine:**
- Propine has the structure: HC≡C-CH3.
- The first carbon (attached to the triple bond) is **sp hybridized**, while the second carbon (attached to a single bond) is **sp³ hybridized**.
- The presence of sp³ hybridized carbon means that the hydrogen atoms attached to it are not in the same plane as the other carbon atoms.
- **Conclusion**: Propine is not a planar molecule.

5. **Analyze Cyclohexene:**
- Cyclohexene has a ring structure with a double bond.
- The carbon atoms in cyclohexene are **sp³ hybridized** in a ring formation.
- The ring structure is not flat; it adopts a three-dimensional shape (like a boat or chair conformation).
- **Conclusion**: Cyclohexene is not a planar molecule.

6. **Final Conclusion:**
- Among the molecules analyzed, only **ethene** is a planar molecule.

### Answer:
The planar molecule among the given options is **Ethene (C2H4)**.