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: 9780135213711Not the one you use?Change textbook

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 94b

Chapter 9, Problem 94b

Draw the resonance contributors for phenol.

Verified step by step guidance

Step 1: Understand the structure of the anilinium ion. The anilinium ion is derived from aniline (C6H5NH2) by protonation of the amino group, resulting in a positively charged nitrogen (NH3+).

Step 2: Recognize that resonance contributors involve the delocalization of electrons. In the anilinium ion, the positive charge on the nitrogen can interact with the π-electrons of the benzene ring.

Step 3: Draw the first resonance structure. This structure shows the positive charge localized on the nitrogen atom, with the benzene ring intact and no movement of π-electrons.

Step 4: Draw the second resonance structure. Move one pair of π-electrons from the benzene ring to form a double bond between the nitrogen and one of the carbon atoms in the ring. This results in the positive charge being delocalized onto the benzene ring.

Step 5: Draw additional resonance structures by moving the π-electrons around the benzene ring. Each structure will show the positive charge delocalized on different carbon atoms of the ring, maintaining the overall stability of the ion through resonance.

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Key Concepts

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

Resonance Structures

Resonance structures are different Lewis structures for the same molecule that depict the delocalization of electrons. In the case of the anilinium ion, resonance contributors illustrate how the positive charge can be distributed across the aromatic ring, enhancing stability. These structures are not real entities but rather a way to represent the hybridization of electron density in a molecule.

Anilinium Ion

The anilinium ion is the protonated form of aniline, characterized by a positively charged nitrogen atom bonded to a phenyl group. This ion is important in organic chemistry as it demonstrates how aromatic systems can stabilize positive charges through resonance. Understanding its structure helps in predicting its reactivity and interactions in various chemical environments.

Aromaticity

Aromaticity refers to the enhanced stability of cyclic, planar molecules with conjugated pi electron systems that follow Hückel's rule (4n + 2 pi electrons). In the context of the anilinium ion, the aromatic ring contributes to the stability of the positive charge through resonance, making it a key concept in understanding the behavior of such ions in chemical reactions.

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Related Practice

Textbook Question

Draw the resonance contributors for the phenolate ion.

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Textbook Question

Protonated cyclohexylamine has a Ka = 1 * 10-11. Using the same sequence of steps as in Problem 94, determine which is a stronger base: cyclohexylamine

or aniline.

e. Which has a greater Ka: cyclohexylammmonium ion or anilinium ion?

f. Which is a stronger acid: cyclohexylamine or aniline?

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Textbook Question

How would the following substituents affect the rate of a Diels–Alder reaction?

b. an electron-donating substituent in the dienophile

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Textbook Question

e. Which has a greater Ka: cyclohexanol or phenol?