Which of the following compounds would you expect to have a dipole moment ?

Options

A.
B.
C.
D.

Answer

To determine which of the given compounds has a dipole moment, we need to analyze the molecular geometry and the electronegativity of the atoms involved in each compound. A dipole moment occurs when there is a separation of charge due to differences in electronegativity between atoms, leading to a polar bond.

Let's break down the analysis step by step:

### Step 1: Identify the Compounds
We need to identify the compounds in question. The video mentions compounds involving NO2 and benzene, CN, and Cl.

### Step 2: Analyze the First Compound (NO2 with Benzene)
- The first compound involves a benzene ring and NO2 groups.
- Benzene is a symmetrical, planar structure, which is non-polar due to the equal distribution of electron density.
- The NO2 group is polar due to the electronegativity difference between nitrogen and oxygen, but since there are two NO2 groups symmetrically placed, their dipole moments will cancel each other out.
- **Conclusion**: This compound does not have a dipole moment.

### Step 3: Analyze the Second Compound (CN)
- The second compound also involves CN groups.
- Similar to the first case, if CN groups are symmetrically placed, the dipole moments will cancel out.
- **Conclusion**: This compound does not have a dipole moment.

### Step 4: Analyze the Third Compound (Cl)
- The third compound involves chlorine (Cl) atoms.
- If Cl atoms are symmetrically placed above and below, their dipole moments will also cancel out.
- **Conclusion**: This compound does not have a dipole moment.

### Step 5: Analyze the Fourth Compound (Meta-chlorobenzene)
- The last compound mentioned is meta-chlorobenzene.
- In this case, the chlorine atoms are not symmetrically placed. The angle between the dipole moments of the Cl atoms is 120 degrees.
- The dipole moments will not cancel out completely due to this angle, resulting in a net dipole moment.
- **Conclusion**: This compound has a dipole moment.

### Final Answer
The compound that would be expected to have a dipole moment is **meta-chlorobenzene**.

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