Textbook Question
Draw resonance contributors for each of the following species and rank them in order of decreasing contribution to the resonance hybrid. Then draw the resonance hybrid.
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1. A Review of General Chemistry
Resonance Structures
Problem 21a
Textbook Question
Draw the resonance contributors for the following radicals:
a. 
Verified step by step guidance1
Identify the structure of the radical provided in the problem. A radical is a species with an unpaired electron, typically represented as a dot next to the atom where the unpaired electron resides.
Determine if the radical is in a conjugated system. Conjugation occurs when there are alternating single and double bonds, allowing for delocalization of electrons.
Draw the first resonance structure by moving electrons. For radicals, this involves moving a single electron and a pair of electrons (from a π bond or lone pair) to create a new resonance contributor. Use curved arrows to indicate the movement of electrons: a single-headed arrow (fishhook) for a single electron and a double-headed arrow for an electron pair.
Repeat the process to generate additional resonance contributors. Ensure that the unpaired electron remains on atoms capable of stabilizing it (e.g., atoms with lower electronegativity or those that can delocalize the radical through resonance).
Verify that all resonance contributors follow the rules of resonance: the overall charge and number of electrons must remain the same, and atoms should not exceed their octet (except for elements that can expand their octet, such as sulfur or phosphorus).
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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 radicals and other reactive intermediates. Understanding resonance is crucial for predicting the reactivity and stability of organic compounds.
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Radicals
Radicals are species that contain an unpaired electron, making them highly reactive. They can be formed through various processes, such as homolytic bond cleavage. The presence of radicals in a molecule can significantly influence its chemical behavior, and drawing resonance contributors helps visualize how the unpaired electron can be delocalized across different atoms.
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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 often represented through resonance structures and is key to understanding the stability of radicals and other reactive intermediates. Delocalization can lower the energy of a molecule, making it more stable and less reactive.
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