What is the value of n in Hückel's rule when a compound has nine pairs of π\pi electrons? b. Is such a compound aromatic?

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

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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

Problem 49a

Chapter 9, Problem 49a

What is the value of n in Hückel's rule when a compound has nine pairs of $π$ electrons? b. Is such a compound aromatic?

Verified step by step guidance

Step 1: Recall Hückel's rule, which states that a compound is aromatic if it has a planar, cyclic, conjugated π-electron system with a total of (4n + 2) π-electrons, where n is a non-negative integer (n = 0, 1, 2, ...).

Step 2: Identify the total number of π-electrons in the compound. The problem states that the compound has nine pairs of π-electrons. Since each pair contains 2 electrons, the total number of π-electrons is 9 × 2 = 18.

Step 3: Set up the equation for Hückel's rule: $ 4n + 2 = 18 $. Solve for $ n $ by isolating it on one side of the equation.

Step 4: Check if the value of $ n $ obtained is a non-negative integer. If it is, the compound satisfies Hückel's rule and is aromatic. If not, the compound is not aromatic.

Step 5: Conclude whether the compound is aromatic based on the value of $ n $ and the conditions of Hückel's rule.

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Key Concepts

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

Hückel's Rule

Hückel's Rule is a criterion for determining the aromaticity of cyclic compounds. It states that a planar, cyclic molecule is aromatic if it contains 4n + 2 π electrons, where n is a non-negative integer. This rule helps predict the stability and reactivity of aromatic compounds based on their electron configuration.

Aromaticity

Aromaticity refers to the special stability and unique properties of certain cyclic compounds due to their delocalized π electrons. Aromatic compounds typically exhibit resonance, which lowers their energy and increases stability. To be classified as aromatic, a compound must meet Hückel's Rule and possess a continuous ring of p orbitals.

π Electrons

π electrons are the electrons found in the p orbitals of a molecule that participate in π bonding. In the context of aromatic compounds, these electrons are crucial for delocalization, which contributes to the compound's stability. The total number of π electrons in a cyclic compound determines its adherence to Hückel's Rule and its aromatic character.

What is the value of n in Hückel's rule when a compound has nine pairs of π\(\pi\) electrons? b. Is such a compound aromatic?