Point out the flaws in the following incorrect Grignard syntheses.
(b)

Verified step by step guidance

1. Step 1: Analyze the starting material. The compound contains a bromine atom attached to a cyclohexane ring with a ketone and an ester functional group. The bromine atom is intended to form a Grignard reagent when treated with magnesium in ether.
2. Step 2: Understand the reaction conditions. The first step involves the formation of the Grignard reagent (R-MgBr) by reacting the bromine-containing compound with magnesium in ether. The second step involves the reaction of the Grignard reagent with formaldehyde (H₂C=O), followed by acidic workup (H₃O⁺).
3. Step 3: Identify the flaw in the synthesis. The ketone and ester functional groups present in the starting material are reactive toward Grignard reagents. When the Grignard reagent is formed, it will likely react intramolecularly with the ketone or ester group, leading to side reactions or decomposition, rather than reacting with formaldehyde as intended.
4. Step 4: Explain why the desired product cannot be formed. The Grignard reagent is highly nucleophilic and will attack the electrophilic carbonyl groups (ketone and ester) within the same molecule, preventing the reaction with formaldehyde. This intramolecular reaction disrupts the intended synthesis pathway.
5. Step 5: Suggest a correction. To avoid this issue, the ketone and ester groups should be protected before forming the Grignard reagent, or a different synthetic route should be chosen that does not involve the formation of a Grignard reagent in the presence of reactive carbonyl groups.

Key Concepts

Grignard Reagents

Grignard reagents are organomagnesium compounds that are highly reactive and used to form carbon-carbon bonds. They are created by reacting alkyl or aryl halides with magnesium in dry ether. Understanding their reactivity is crucial, as they can react with electrophiles, including carbonyl compounds, to form alcohols. In the given synthesis, the presence of a carbonyl group is essential for the reaction to proceed correctly.

Electrophilic Addition

Electrophilic addition is a fundamental reaction mechanism in organic chemistry where an electrophile reacts with a nucleophile to form a new bond. In the context of Grignard reactions, the Grignard reagent acts as a nucleophile, attacking the electrophilic carbon of a carbonyl compound. The failure to recognize the correct electrophile or the presence of incompatible functional groups can lead to flawed syntheses, as seen in the provided example.

Functional Group Compatibility

Functional group compatibility refers to the ability of different functional groups to coexist and react without interfering with each other. In organic synthesis, certain groups can be sensitive to the conditions or reagents used, leading to undesired reactions or products. In the provided synthesis, the presence of multiple oxygen-containing functional groups may hinder the desired reaction pathway, resulting in an incorrect product.