Draw the Lewis structure of the methoxide ion ( CH3O-). Draw the Lewis structure of a proton (H+) . To which atom of methoxide would you expect a proton to add?

Ch. 4 - Acids and Bases: Electron Flow

Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition

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Ch. 4 - Acids and Bases: Electron Flow

Problem 3

Chapter 3, Problem 3

Draw the Lewis structure of the methoxide ion ( CH₃O^-). Draw the Lewis structure of a proton (H⁺) . To which atom of methoxide would you expect a proton to add?

Verified step by step guidance

Step 1: Begin by understanding the methoxide ion (CH₃O⁻). Methoxide consists of a methyl group (CH₃) bonded to an oxygen atom. The negative charge indicates that the oxygen atom has an extra electron, making it more nucleophilic.

Step 2: Draw the Lewis structure of the methoxide ion. Represent the methyl group (CH₃) with three hydrogen atoms bonded to a central carbon atom. The carbon atom is single-bonded to the oxygen atom, which has three lone pairs of electrons and a negative charge. Use MathML to represent the structure:

{CH}_{3} - O -

Step 3: Draw the Lewis structure of a proton (H⁺). A proton is simply a hydrogen atom that has lost its electron, leaving it with a positive charge. Represent it as

H +

Step 4: Analyze the methoxide ion to determine where the proton (H⁺) would likely add. The oxygen atom in methoxide has a negative charge and lone pairs of electrons, making it highly nucleophilic and the most likely site for protonation.

Step 5: Conclude that the proton (H⁺) would add to the oxygen atom in methoxide, forming methanol (CH₃OH). This is because the oxygen atom is the most electron-rich and reactive site in the molecule.

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Key Concepts

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

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They use dots to represent valence electrons and lines to represent bonds. Understanding how to draw Lewis structures is essential for visualizing molecular geometry and predicting reactivity.

Methoxide Ion

The methoxide ion (CH₃O⁻) is a negatively charged species formed when methanol (CH₃OH) loses a proton (H⁺). In its Lewis structure, the oxygen atom carries a negative charge and is bonded to a carbon atom and a hydrogen atom. This ion is a strong nucleophile, meaning it readily donates its electron pair to form new bonds.

Proton Affinity

Proton affinity refers to the tendency of a molecule or ion to attract and bond with a proton (H⁺). In the case of the methoxide ion, the oxygen atom, which has a lone pair of electrons, is the most likely site for protonation due to its high electronegativity and ability to stabilize the positive charge after bonding with a proton.