Which of the following resonance strutuers is the major contributor to the resonance hybrid ?
`CH_(3)-CH_(2)underset((I))(-)overset(o+)(CH)-underset(* *)overset(* *)(O)Me hArr CH_(3)-CH_(2)underset((II))(-)CH=underset(* *)overset(o+)(O) Me`

Options

A. I
B. II
C. Both have equal contrbution
D. They are not resonance structures

Explanation

To determine which resonance structure is the major contributor to the resonance hybrid, we need to analyze both resonance structures (I and II) based on several criteria for stability and contribution to the resonance hybrid.

### Step 1: Analyze the Octet Rule
- **Resonance Structure I**:
- The carbon atom has 4 bonds (2 with hydrogen and 2 with oxygen), which means it has 8 electrons around it. Therefore, the octet is complete for carbon.
- The oxygen atom has 2 bonds and 1 lone pair, totaling 6 electrons, which means it does not have a complete octet.

- **Resonance Structure II**:
- The carbon atom has 4 bonds (2 with hydrogen and 2 with oxygen), which means it has 8 electrons around it. Therefore, the octet is complete for carbon.
- The oxygen atom has 2 bonds and 1 lone pair, totaling 6 electrons, which means it does not have a complete octet.

### Step 2: Evaluate Charge Distribution
- In Structure I, there is a negative charge on the carbon atom, which is less electronegative than oxygen. This is less favorable.
- In Structure II, the negative charge is on the oxygen atom, which is more electronegative. This is more favorable.

### Step 3: Compare Stability
- Structure I has a negative charge on carbon, which is not ideal because carbon is less electronegative than oxygen.
- Structure II has the negative charge on oxygen, which is more stable due to the electronegativity of oxygen.

### Conclusion
Based on the analysis:
- **Resonance Structure II** is the major contributor to the resonance hybrid because it has a complete octet for carbon, the negative charge is placed on the more electronegative atom (oxygen), and overall, it is more stable than Structure I.

### Final Answer
The major contributor to the resonance hybrid is **Resonance Structure II**.

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