Textbook Question
For each of the molecules shown, do the following:
(i) Identify all pushable pairs.
(ii) Identify all places where electrons can be pushed.
(iii) Draw one valid resonance structure.
(a)
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1. A Review of General Chemistry
Resonance Structures
Problem 64f
Textbook Question
Two resonance structures are shown for each molecule. Use the arrow-pushing formalism to represent the electron flow from the structure on the left to the one on the right.
(f) 
Verified step by step guidance1
Step 1: Identify the resonance structures provided in the problem. Resonance structures differ in the placement of electrons, specifically π-electrons and lone pairs, while the arrangement of atoms remains the same.
Step 2: Locate the regions in the molecule where electron movement occurs. Typically, this involves π-bonds, lone pairs, or formal charges. Look for areas where electrons can delocalize to stabilize the molecule.
Step 3: Use curved arrows to represent the movement of electrons. A curved arrow starts at the source of electrons (a lone pair or a bond) and points to where the electrons are moving. Ensure the arrows follow the rules of electron flow: electrons move from areas of high electron density to areas of lower electron density.
Step 4: Verify that the resulting resonance structure adheres to the rules of resonance. The connectivity of atoms must remain unchanged, and the total number of electrons must be conserved. Ensure that formal charges are correctly assigned in the new structure.
Step 5: Confirm that the resonance structures are valid and contribute to the resonance hybrid. Resonance structures should differ only in the placement of electrons, not the arrangement of atoms, and should follow the octet rule where applicable.
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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 ways of drawing the same molecule that illustrate the delocalization of electrons. They are used to represent molecules that cannot be accurately depicted by a single Lewis structure. Each resonance structure contributes to the overall hybrid structure, which is a more accurate representation of the molecule's electron distribution.
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Arrow-Pushing Formalism
Arrow-pushing formalism is a method used in organic chemistry to depict the movement of electrons during chemical reactions. Arrows indicate the direction of electron flow, with a double-headed arrow showing the movement of a pair of electrons and a single-headed arrow indicating the movement of a single electron. This technique helps visualize how bonds are formed and broken in chemical transformations.
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Electron Delocalization
Electron delocalization refers to the phenomenon where electrons are spread over several atoms rather than being localized between two atoms. This occurs in resonance structures, where the electrons can occupy multiple positions, leading to increased stability of the molecule. Delocalization is a key factor in understanding the reactivity and properties of organic compounds.
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