Which one of the following compounds is not planar?

Options

A. `CH_2 = C = CH_2`
B. `CH_2= CH_2`
C. `CH _2= CH - CH = CH_2`
D. `CH_2 = CH – C H= CH`

Answer

To determine which compound is not planar, we need to analyze the hybridization and geometry of the compounds given in the options. Let's break down the steps:

### Step 1: Identify the Hybridization of Atoms
- For each compound, identify the hybridization of the carbon atoms involved.
- Carbon atoms can be sp, sp², or sp³ hybridized.
- sp hybridization leads to linear geometry, sp² leads to trigonal planar, and sp³ leads to tetrahedral geometry.

### Step 2: Analyze the Presence of Pi Bonds
- Check for the presence of double bonds (pi bonds) between carbon atoms.
- The presence of adjacent pi bonds can lead to non-planarity due to steric hindrance or the arrangement of the pi bonds in different planes.

### Step 3: Evaluate Each Compound
- **Option 1**: CH₂=CH-CH=C (this compound has adjacent double bonds, leading to non-planarity).
- **Option 2**: CH₂=CH-CH₃ (this compound has one double bond, and all atoms are in the same plane).
- **Option 3**: CH₃-CH=CH₂ (this compound has one double bond, and all atoms are in the same plane).
- **Option 4**: C≡C-CH₂ (this compound has a triple bond, which is linear).

### Step 4: Conclusion
- Based on the analysis, **Option 1** is the compound that is not planar due to the presence of adjacent double bonds, which causes the terminal atoms to be in different planes.

### Final Answer
**Option 1** is the correct answer as it is not planar.

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