Which of these molecules does not exhibit resonance ?

Options

A. Ozone
B. Phenol
C. But -1,3-diene
D. ethanol

Answer

To determine which molecule does not exhibit resonance, we need to understand the concept of resonance and conjugation.

### Step 1: Define Resonance and Conjugation
Resonance occurs in molecules where there are multiple valid Lewis structures (resonance structures) that can be drawn, which differ only in the placement of electrons. For resonance to occur, there must be conjugation, which is the presence of alternating single and multiple bonds or lone pairs that can participate in resonance.

### Step 2: Analyze the Given Molecules
We will analyze the resonance capability of each molecule mentioned in the video transcript:

1. **Ozone (O3)**: Ozone has a structure where there are alternating double bonds and lone pairs. This allows for resonance as the electrons can be delocalized. Therefore, ozone exhibits resonance.

2. **Phenol (C6H5OH)**: Phenol has a hydroxyl group (-OH) attached to a benzene ring. The lone pair on the oxygen can participate in resonance with the π-electrons of the benzene ring, allowing for multiple resonance structures. Thus, phenol exhibits resonance.

3. **Buta-1,3-diene (C4H6)**: This molecule has alternating double bonds. The structure allows for the delocalization of π-electrons, leading to resonance. Buta-1,3-diene exhibits resonance.

4. **Ethanol (C2H5OH)**: Ethanol has a simple structure with a hydroxyl group attached to an ethyl group. There are no alternating double bonds or lone pairs that can participate in resonance. Therefore, ethanol does not exhibit resonance.

### Conclusion
Among the molecules analyzed, **ethanol** is the one that does not exhibit resonance due to the lack of conjugation.