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Ch. 21 - Conjugated Systems I: Stability and Addition Reactions
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
Chapter 20, Problem 2b

Draw all possible resonance structures for the reactive intermediates shown.
(b) Chemical structure diagram showing a benzene ring with a carbonyl group and a reactive intermediate for resonance structure analysis.

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1
Identify the reactive intermediate in the given structure. Reactive intermediates can include carbocations, carbanions, radicals, or other species. Look for atoms with formal charges or unpaired electrons.
Determine the location of π-electrons (double bonds) and lone pairs in the molecule. These are the key contributors to resonance structures as they can delocalize to stabilize the intermediate.
Apply the resonance rules: Move π-electrons or lone pairs to adjacent atoms or bonds while ensuring that the octet rule is not violated for second-row elements (e.g., carbon, nitrogen, oxygen). Use curved arrows to indicate the movement of electrons.
Draw each resonance structure that results from the electron movement. Ensure that all resonance structures are valid Lewis structures, with correct formal charges assigned to atoms.
Verify that all resonance structures contribute to the overall resonance hybrid. Highlight the most stable resonance structure based on factors such as the placement of charges (e.g., negative charges on more electronegative atoms) and the minimization of formal charges.

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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 same arrangement of atoms but differ in the distribution of electrons. These structures help illustrate the delocalization of electrons within a molecule, which can stabilize reactive intermediates. Understanding resonance is crucial for predicting the reactivity and stability of organic compounds.
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Reactive Intermediates

Reactive intermediates are transient species that form during the conversion of reactants to products in a chemical reaction. Common types include carbocations, carbanions, and free radicals. Their stability and reactivity are often influenced by resonance, making it essential to analyze their resonance structures to understand their behavior in reactions.
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Electron Delocalization

Electron delocalization refers to the distribution of electrons across multiple atoms in a molecule, rather than being localized between two atoms. This phenomenon is a key feature of resonance structures, as it allows for the stabilization of reactive intermediates. Recognizing how electrons can be shared among different atoms helps in predicting the stability and reactivity of organic compounds.
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