Textbook Question
Which has the greater delocalization energy?
16. Conjugated Systems
Stability of Conjugated Intermediates
3:42 minutesProblem 27a
Textbook Question
Draw the important resonance contributors for the following cations, anions, and radicals.
(a) 
Verified step by step guidance1
Step 1: Identify the structure provided in the image. The molecule contains a carbocation (CH2+) attached to a conjugated system of double bonds. This indicates that resonance contributors can be drawn by delocalizing the positive charge across the π-system.
Step 2: Begin by moving the π-electrons from the double bond adjacent to the carbocation towards the carbocation. This creates a new resonance structure where the positive charge is shifted to the carbon atom that was part of the double bond.
Step 3: Continue the resonance process by moving the π-electrons from the next double bond in the conjugated system towards the newly formed carbocation. This results in another resonance structure where the positive charge is further delocalized.
Step 4: Repeat the process for the remaining double bond in the conjugated system, ensuring that the positive charge is distributed across the entire π-system. Each resonance structure should maintain the overall charge and connectivity of the molecule.
Step 5: Verify that all resonance contributors are valid by checking that each structure adheres to the rules of resonance (e.g., no violation of the octet rule, proper placement of charges). Highlight the delocalization of the positive charge as the key stabilizing feature of the molecule.
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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 help in understanding the stability and reactivity of a compound. In resonance, the actual structure is a hybrid of these contributors, which can affect properties like acidity, basicity, and reactivity.
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Cation Stability
Cation stability refers to the relative stability of positively charged species. Factors influencing cation stability include the degree of alkyl substitution, resonance stabilization, and the electronegativity of adjacent atoms. More stable cations are generally formed from structures that allow for greater electron delocalization.
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Electron Delocalization
Electron delocalization occurs when electrons are spread over multiple atoms rather than localized between two. This phenomenon is crucial in resonance structures, as it allows for the stabilization of charged species like cations and anions. Delocalization can lower the energy of a molecule, making it more stable and less reactive.
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