Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene

Bruice8th EditionOrganic ChemistryISBN: 9780135213711Non è quello che usi tu?Cambia libro di testo

Bruice 8th Edition

Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene

Problema 68(14)

Capitolo 8, Problema 68(14)

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?
14.

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Identify the species in question and determine if it has a conjugated π-system or lone pairs adjacent to π-bonds, as these are key indicators of resonance potential.

Draw the Lewis structure of the species, ensuring all valence electrons are accounted for, and identify atoms or groups that can participate in resonance (e.g., lone pairs, π-bonds, or charges).

Using curved arrows, show the movement of electrons to generate possible resonance contributors. Ensure that each resonance structure follows the rules of valence and does not violate the octet rule (except for elements that can expand their octet, such as sulfur or phosphorus).

Evaluate the stability of each resonance contributor by considering factors such as the placement of charges (negative charges on more electronegative atoms, positive charges on less electronegative atoms), the number of covalent bonds, and the absence of formal charges when possible. Label the major contributors (more stable) and minor contributors (less stable).

For part b, examine the resonance contributors of each species. If all contributors have equivalent stability (e.g., identical structures with charges or bonds distributed symmetrically), then they contribute equally to the resonance hybrid. Otherwise, note the unequal contributions.

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Resonance Structures

Resonance structures are different Lewis structures for the same 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 contributors.

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Drawing Resonance Structures

Major and Minor Contributors

In resonance theory, not all resonance structures contribute equally to the resonance hybrid. Major contributors are those that are more stable, typically having full octets, minimal formal charges, and favorable charge distributions. Minor contributors, on the other hand, may have significant formal charges or violate the octet rule, making them less stable and thus contributing less to the overall resonance hybrid.

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Resonance Hybrid

The resonance hybrid is the actual structure of a molecule that results from the combination of all its resonance contributors. It reflects the delocalization of electrons across the molecule, leading to increased stability. The hybrid is often represented by a single structure with partial bonds or charges, indicating that the true electronic structure is a blend of the contributing forms rather than any single resonance structure.

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How to draw a resonance hybrid.

Pratica correlata

Domanda del libro di testo

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.