a. Draw resonance contributors for the following species. Do not include structures that are so unstable that their contributions to the resonance hybrid would be negligible. Indicate which are major contributors and which are minor contributors to the resonance hybrid.
b. Do any of the species have resonance contributors that all contribute equally to the resonance hybrid?

1. CH₃CH=CHOCH₃

Verified step by step guidance

1. Identify the species in question and determine if it has delocalized electrons, such as lone pairs, π bonds, or charges, which can participate in resonance.
2. Draw all possible resonance contributors by moving electrons (using curved arrows) while adhering to the rules of resonance: (1) Do not break single bonds, (2) Maintain the correct number of valence electrons, and (3) Ensure that atoms do not exceed their octet (except for elements that can expand their octet, like sulfur or phosphorus).
3. Evaluate the stability of each resonance contributor by considering factors such as: (1) Full octets on atoms, (2) Minimal formal charges, (3) Negative charges on more electronegative atoms, and (4) Positive charges on less electronegative atoms. Label the major contributors (most stable) and minor contributors (less stable).
4. For part b, analyze the resonance contributors to determine if they are all equivalent in terms of stability. If all contributors have the same structure and stability (e.g., equivalent formal charges and atom arrangements), they contribute equally to the resonance hybrid.
5. Summarize your findings by indicating which contributors are major or minor and whether any species have resonance contributors that contribute equally to the resonance hybrid.

Key Concepts

Resonance Structures

Resonance structures are different Lewis structures for a molecule that depict the same arrangement of atoms but differ in the placement of electrons. These structures help illustrate the delocalization of electrons within a molecule, which contributes to its stability. The actual structure of the molecule is a resonance hybrid, a weighted average of all valid resonance forms, where more stable forms contribute more to the hybrid.

Major and Minor Contributors

In resonance theory, major contributors are resonance structures that are more stable and thus have a greater influence on the resonance hybrid. Factors such as the octet rule, formal charges, and electronegativity determine the stability of these structures. Minor contributors, while still valid, are less stable and contribute less to the overall resonance hybrid, often due to unfavorable charge distributions or incomplete octets.

Equally Contributing Resonance Structures

Some molecules may have resonance contributors that are equally stable, meaning they contribute equally to the resonance hybrid. This occurs when all structures satisfy the octet rule, have minimal formal charges, and maintain similar energy levels. Identifying such structures is crucial for understanding the overall electronic distribution in the molecule, as it indicates a high degree of delocalization and stability.