In which of the following pairs of resonance contributors is the sturcture on the right a important contributor?

Options

A. `H-overset(o+)C=overset(* *)O:harrH-C-=overset(o+)O:`
B. `overset(Ɵ)CH_(2)-overset(o+)N-=overset(* *)NharrCH_(2)=overset(o+)N=overset(Ɵ)N`
C. `CH_(3)-overset(o+)CH-underset(* *)overset(* *)OHharrCH_(3)-CH=underset(* *) overset(o+)OH`
D. All of the above

Answer

To determine which of the resonance contributors in the given pairs has the structure on the right as an important contributor, we need to analyze the stability of each structure based on the following criteria:

1. **Octet Rule**: The most stable resonance structures will have atoms that satisfy the octet rule (i.e., have eight electrons in their valence shell).
2. **Charge Distribution**: Structures that minimize formal charges and place negative charges on more electronegative atoms are generally more stable.
3. **Bonding**: Structures that have more covalent bonds and fewer charges are preferred.

### Step-by-Step Solution:

**Step 1: Identify the Resonance Structures**
- Look at the pairs of resonance structures provided in the question.

**Step 2: Check the Octet Rule**
- For each structure, check if all atoms have a complete octet. Count the number of bonds around each atom.

**Step 3: Analyze Formal Charges**
- Calculate the formal charges for each atom in the resonance structures. The formula for formal charge is:
\[ \text{Formal Charge} = \text{Valence Electrons} - \text{Non-bonding Electrons} - \frac{1}{2} \times \text{Bonding Electrons} \]
- Structures with lower formal charges are generally more stable.

**Step 4: Evaluate Electronegativity**
- If there are charges present, check if negative charges are on more electronegative atoms. This increases stability.

**Step 5: Compare Stability**
- Compare the stability of the structures based on the octet rule, formal charges, and electronegativity. The structure that is more stable and has a complete octet will be the more important contributor.

**Step 6: Conclusion**
- After evaluating all structures, determine which structure on the right is the most important contributor based on the criteria above.