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Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 23 - Benzene I: Aromatic Stability and Substitution ReactionsProblem 61h
Chapter 22, Problem 61h

(i) Classify the following molecules as aromatic, nonaromatic, or antiaromatic.
(ii) For aromatic molecules, solve for n in Hückel’s rule. For all other molecules, explain which rule of aromaticity is being broken.
(h) Chemical structure diagram illustrating a molecule for classification as aromatic, nonaromatic, or antiaromatic.

Verified step by step guidance
1
Identify the structure: The molecule shown is a cyclic compound with alternating single and double bonds, forming a ring structure.
Count the number of π-electrons: In this structure, each double bond contributes two π-electrons. Count the total number of π-electrons in the ring.
Apply Hückel's rule: Aromatic compounds must satisfy Hückel's rule, which states that a molecule is aromatic if it has (4n + 2) π-electrons, where n is a non-negative integer. Check if the number of π-electrons fits this formula.
Check planarity and cyclic nature: For a molecule to be aromatic, it must be cyclic, planar, and fully conjugated. Ensure that the molecule meets these criteria.
Determine aromaticity: Based on the π-electron count and structural criteria, classify the molecule as aromatic, nonaromatic, or antiaromatic. If aromatic, solve for n in Hückel's rule. If not, explain which rule of aromaticity is being broken.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Aromaticity

Aromaticity refers to a property of cyclic compounds that exhibit enhanced stability due to the delocalization of π electrons across the ring structure. For a molecule to be classified as aromatic, it must be cyclic, planar, fully conjugated, and follow Hückel's rule, which states that the number of π electrons must equal 4n + 2, where n is a non-negative integer.
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Hückel's Rule

Hückel's rule is a criterion used to determine the aromaticity of a cyclic compound. It states that a planar, cyclic molecule with a continuous overlap of p-orbitals is aromatic if it contains 4n + 2 π electrons, where n is an integer (0, 1, 2, ...). This rule helps in identifying stable aromatic compounds and differentiating them from nonaromatic and antiaromatic compounds.
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Anti-aromaticity

Anti-aromaticity is a property of cyclic compounds that leads to instability due to the presence of 4n π electrons, which results in a destabilizing effect. Unlike aromatic compounds, anti-aromatic compounds do not satisfy Hückel's rule and are typically less stable, often leading to higher reactivity. Understanding the distinction between aromatic, nonaromatic, and anti-aromatic compounds is crucial for predicting their chemical behavior.
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Related Practice
Textbook Question

(i) Classify the following molecules as aromatic, nonaromatic, or antiaromatic.

(ii) For aromatic molecules, solve for n in Hückel’s rule. For all other molecules, explain which rule of aromaticity is being broken.

(e)

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Textbook Question

Use a Frost circle diagram to construct the molecular orbital diagram for the molecules shown. Would you expect them to be aromatic or antiaromatic?

(a)

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Textbook Question

Use a Frost circle diagram to construct the molecular orbital diagram for the molecules shown. Would you expect them to be aromatic or antiaromatic?

(b) 

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Textbook Question

(i) Classify the following molecules as aromatic, nonaromatic, or antiaromatic.

(ii) For aromatic molecules, solve for n in Hückel’s rule. For all other molecules, explain which rule of aromaticity is being broken.

(g)

Textbook Question

(i) Classify the following molecules as aromatic, nonaromatic, or antiaromatic.

(ii) For aromatic molecules, solve for n in Hückel’s rule. For all other molecules, explain which rule of aromaticity is being broken.

(f)

1
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