Which of the following hydrocarbons has the lowest dipole moment.

Options

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

Explanation

To determine which hydrocarbon has the lowest dipole moment, we need to analyze the molecular structure and the arrangement of dipole moments for each given hydrocarbon. Here’s a step-by-step solution:

### Step 1: Understand Dipole Moment
The dipole moment is a measure of the polarity of a molecule. It occurs due to the difference in electronegativity between atoms, leading to a separation of charge. Molecules with symmetrical structures often have dipole moments that cancel out, resulting in a net dipole moment of zero.

### Step 2: Analyze Each Hydrocarbon
We will analyze each hydrocarbon provided in the options to determine their dipole moments.

#### Option A: Hydrocarbon A
1. **Structure**: Analyze the molecular structure.
2. **Dipole Moments**: Identify the dipole moments based on electronegativity differences.
3. **Result**: Check if the dipole moments cancel out or not.

#### Option B: CH3-C≡C-CH3
1. **Structure**: This molecule has a symmetrical structure with a triple bond.
2. **Dipole Moments**: The sp hybridized carbon is more electronegative than the sp3 hybridized carbon, leading to dipole moments that cancel out.
3. **Result**: The net dipole moment (μ net) is zero.

#### Option C: CH3-CH=CH-CH2
1. **Structure**: Analyze the molecular structure.
2. **Dipole Moments**: Identify the dipole moments.
3. **Result**: The dipole moments do not cancel out completely, resulting in a non-zero dipole moment.

#### Option D: CH3-CH2-C≡CH
1. **Structure**: Analyze the molecular structure.
2. **Dipole Moments**: Identify the dipole moments.
3. **Result**: The dipole moments do not cancel out, resulting in a non-zero dipole moment.

### Step 3: Conclusion
After analyzing all the options:
- **Option A** has a non-zero dipole moment.
- **Option B** has a dipole moment of zero (lowest).
- **Option C** has a non-zero dipole moment.
- **Option D** has a non-zero dipole moment.

Thus, the hydrocarbon with the lowest dipole moment is **Option B: CH3-C≡C-CH3**.