Label the reactants in these acid–base reactions as Lewis acids (electrophiles) or Lewis bases (nucleophiles). Use curved arrows to show the movement of electron pairs in the reactions.
(a)

Verified step by step guidance

1. Identify the reactants: CH3O- (methoxide ion) and CH3Cl (methyl chloride).
2. Determine the role of each reactant: CH3O- is a Lewis base (nucleophile) because it donates an electron pair, and CH3Cl is a Lewis acid (electrophile) because it accepts an electron pair.
3. Use curved arrows to show the movement of electron pairs: Draw a curved arrow from the lone pair on the oxygen of CH3O- to the carbon atom in CH3Cl, indicating the formation of a new bond.
4. Recognize the leaving group: The Cl atom in CH3Cl will leave as Cl-, taking the electron pair from the C-Cl bond.
5. Write the products: The reaction forms CH3OCH3 (dimethyl ether) and Cl- (chloride ion).

Key Concepts

Lewis Acids and Bases

Lewis acids are defined as electron pair acceptors, while Lewis bases are electron pair donors. In the context of acid-base reactions, identifying which species acts as a Lewis acid or base is crucial for understanding the reaction mechanism. For example, in the provided reaction, the negatively charged methoxide ion (CH3O⁻) acts as a Lewis base, donating an electron pair, while the methyl chloride (CH3Cl) acts as a Lewis acid, accepting the electron pair.

Curved Arrows in Mechanisms

Curved arrows are used in organic chemistry to illustrate the movement of electron pairs during chemical reactions. The tail of the arrow indicates the source of the electron pair, while the head points to the atom that will receive the electrons. This notation helps visualize the flow of electrons, which is essential for understanding reaction mechanisms, such as the nucleophilic attack of the methoxide ion on the electrophilic carbon of methyl chloride.

Nucleophiles and Electrophiles

Nucleophiles are species that have a high electron density and can donate an electron pair to form a bond, while electrophiles are electron-deficient species that can accept an electron pair. In the given reaction, the methoxide ion serves as a nucleophile, attacking the electrophilic carbon in methyl chloride. Recognizing these roles is fundamental for predicting the outcome of reactions and understanding the stability of intermediates formed during the process.