Show how you would accomplish the following synthetic conversions by adding an organolithium reagent to an acid.
(a)

Verified step by step guidance

1. Step 1: Analyze the starting material and product. The starting material is benzoic acid (C₆H₅COOH), and the product is acetophenone (C₆H₅COCH₃). This transformation involves replacing the carboxylic acid group (-COOH) with a ketone group (-COCH₃).
2. Step 2: Prepare the organolithium reagent. To introduce the methyl group (-CH₃) in the ketone, use methyl lithium (CH₃Li) as the organolithium reagent. Organolithium reagents are highly nucleophilic and react with electrophilic centers.
3. Step 3: React the benzoic acid with the organolithium reagent. The carboxylic acid group (-COOH) reacts with CH₃Li to form an intermediate. The acidic proton of the carboxylic acid is replaced by the lithium ion, forming a lithium carboxylate intermediate.
4. Step 4: Perform a second addition of the organolithium reagent. The lithium carboxylate intermediate reacts further with another equivalent of CH₃Li, leading to the formation of a dianion intermediate. This intermediate undergoes rearrangement to form the ketone product.
5. Step 5: Quench the reaction. After the organolithium reagent has reacted completely, the reaction mixture is quenched with water or a mild acid to neutralize any remaining reactive species and isolate the acetophenone product.

Key Concepts

Organolithium Reagents

Organolithium reagents are highly reactive compounds containing a carbon-lithium bond. They are used as strong nucleophiles in organic synthesis, capable of attacking electrophiles such as carbonyls and halides. Their reactivity allows them to form new carbon-carbon bonds, making them essential for various synthetic transformations.

Acid-Base Reactions

In organic chemistry, acid-base reactions involve the transfer of protons (H+) between species. When an organolithium reagent is added to an acid, it can deprotonate the acid, generating a carbanion. This step is crucial for initiating further reactions, as the resulting carbanion can act as a nucleophile in subsequent steps.

Synthetic Pathways

Synthetic pathways refer to the series of chemical reactions that transform starting materials into desired products. Understanding the mechanism of how organolithium reagents interact with acids is vital for designing efficient synthetic routes. This includes recognizing the intermediates formed and the conditions required for successful conversions.