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Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
Chapter 4, Problem 6b

Provide a reasonable arrow-pushing mechanism for the following Lewis acid–Lewis base reactions.
(b) Lewis acid-base reaction diagram showing hydroxide ion and a Lewis acid forming a new compound with an arrow indicating the reaction direction.

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1
Identify the Lewis acid and Lewis base in the reaction. A Lewis acid is an electron pair acceptor, while a Lewis base is an electron pair donor. Look for species with empty orbitals (Lewis acid) and lone pairs of electrons (Lewis base).
Determine the site of interaction between the Lewis acid and Lewis base. Typically, the lone pair on the Lewis base will attack the electron-deficient center of the Lewis acid.
Draw the curved arrow to represent the movement of electrons. The arrow should start from the lone pair on the Lewis base and point toward the electron-deficient atom of the Lewis acid.
Update the structure of the product formed after the electron pair donation. The Lewis base will form a bond with the Lewis acid, and the electron density will shift accordingly.
Verify the final product to ensure that all atoms obey the octet rule (if applicable) and that charges are properly assigned based on the electron movement.

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Key Concepts

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

Lewis Acids and Bases

Lewis acids are electron pair acceptors, while Lewis bases are electron pair donors. This concept expands the definition of acids and bases beyond protons, allowing for a broader range of chemical reactions. Understanding the nature of these species is crucial for predicting reaction outcomes in organic chemistry.
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The Lewis definition of acids and bases.

Arrow-Pushing Mechanism

Arrow-pushing mechanisms are a way to illustrate the movement of electrons during chemical reactions. Curved arrows represent the flow of electron pairs, indicating how bonds are formed or broken. This visual representation helps in understanding the stepwise progression of reactions, particularly in Lewis acid-base interactions.
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General Mechanism

Reaction Intermediates

In many Lewis acid-base reactions, intermediates are formed as transient species that exist during the reaction process. Recognizing these intermediates is essential for understanding the overall mechanism and predicting the final products. They often play a critical role in determining the reaction pathway and kinetics.
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Stability of Conjugated Intermediates