Which of the following contributing resonance structures is more important in the two examples below? Example 1 H H CIC H H :0: H3C- -CH3 More important resonance structure = Example 2 •o __NH2 More important resonance structure = HC H H CIC H H H3C- :0: ·O· -CH3 -NH₂
Formal Charges
Formal charges have an important role in organic chemistry since this concept helps us to know whether an atom in a molecule is neutral/bears a positive or negative charge. Even if some molecules are neutral, the atoms within that molecule need not be neutral atoms.
Polarity Of Water
In simple chemical terms, polarity refers to the separation of charges in a chemical species leading into formation of two polar ends which are positively charged end and negatively charged end. Polarity in any molecule occurs due to the differences in the electronegativities of the bonded atoms. Water, as we all know has two hydrogen atoms bonded to an oxygen atom. As oxygen is more electronegative than hydrogen thus, there exists polarity in the bonds which is why water is known as a polar solvent.
Valence Bond Theory Vbt
Valence bond theory (VBT) in simple terms explains how individual atomic orbitals with an unpaired electron each, come close to each other and overlap to form a molecular orbital giving a covalent bond. It gives a quantum mechanical approach to the formation of covalent bonds with the help of wavefunctions using attractive and repulsive energies when two atoms are brought from infinity to their internuclear distance.
**Example 2**
In this example, two resonance structures are depicted for another molecule.
- The first resonance structure shows an oxygen atom double-bonded to a carbon atom with two lone pairs of electrons on the oxygen. Adjacent to the carbon, there is an amine group (NH2), and a methyl group (H3C).
- The second resonance structure shows the oxygen atom with the same two lone pairs but now, the nitrogen in the amine group has a positive formal charge and has lost one pair of electrons, which have moved to form a double bond between the carbon and nitrogen atom.
**Example 2 Resonance Structures:**
**Determining More Important Resonance Structures**
Resonance structures can be evaluated based on several principles:
1. **Minimizing Formal Charges:** Structures with fewer formal charges are generally more stable.
2. **Full Octets:** Resonance structures in which atoms (especially carbon, nitrogen, and oxygen) have full octets are usually favored.
3. **Negative Charges on Electronegative Atoms:** It's more favorable for negative charges to reside on more electronegative atoms (like oxygen).
**Interactive Decision Making:**
Each example asks you to determine the more important resonance structure through a dropdown selection:
- **More important resonance structure =** [](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fd32c0099-d35b-45af-b7af-24c06e9e82b9%2F85896978-e277-4cb7-a88c-58f80d82ef28%2Fukua6x_processed.png&w=3840&q=75)
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