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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 61d
Chapter 22, Problem 61d

(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.
(d) Chemical structure of a positively charged nitrogen atom attached to a benzene ring, illustrating aromaticity concepts.

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1
Identify the molecule as pyridinium ion, which is a six-membered ring with a nitrogen atom bearing a positive charge.
Determine the number of π electrons in the ring. Each double bond contributes two π electrons, and there are three double bonds, contributing a total of 6 π electrons.
Apply 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 (6) fits Hückel's rule. Set up the equation 4n + 2 = 6 and solve for n.
Since the equation 4n + 2 = 6 gives a valid integer solution for n, the molecule is classified as aromatic according to Hückel's rule.

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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 it must have 4n + 2 π electrons, 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 compound. It states that a planar, cyclic molecule is aromatic if it contains a total of 4n + 2 π electrons in its conjugated system. This rule helps in identifying aromatic compounds by calculating the number of π electrons and checking if they fit the formula.
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Anti-aromaticity

Anti-aromaticity is a property of cyclic compounds that are destabilized due to the presence of 4n π electrons, which leads to increased energy and instability. Unlike aromatic compounds, anti-aromatic compounds do not satisfy Hückel's rule and often exhibit significant strain or reactivity due to their unfavorable electronic configuration.
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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)

2
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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.

(a)

1
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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.

(c)

1
views
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.

(b)

1
views
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
views