Textbook Question
What products would you expect to obtain from the following reactions?
a. malonic acid + 2 acetyl chloride
22. Carboxylic Acid Derivatives: NAS
Nucleophilic Acyl Substitution
3:09 minutesProblem 37
Textbook Question
Diazomethane can be used to convert a carboxylic acid to a methyl ester. Propose a mechanism for this reaction.
Verified step by step guidance1
Step 1: Identify the reactants and products. The reactants are a carboxylic acid and diazomethane (CH₂N₂). The product is a methyl ester, along with nitrogen gas (N₂) as a byproduct.
Step 2: Recognize the role of diazomethane. Diazomethane is a highly reactive compound that acts as a methylating agent. It donates a methyl group to the carboxylic acid, converting it into a methyl ester.
Step 3: Initiate the mechanism. The carboxylic acid's hydroxyl group (-OH) acts as a nucleophile and attacks the electrophilic carbon in diazomethane. This leads to the formation of a tetrahedral intermediate.
Step 4: Rearrange the intermediate. The intermediate undergoes a rearrangement where the nitrogen atoms in diazomethane are expelled as nitrogen gas (N₂), leaving behind the methyl group attached to the oxygen atom of the carboxylic acid.
Step 5: Finalize the product. The methyl group is now bonded to the oxygen atom of the carboxylic acid, forming the methyl ester. The reaction is complete, and nitrogen gas is released as a byproduct.
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Video duration:
3mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Carboxylic Acids
Carboxylic acids are organic compounds characterized by the presence of a carboxyl group (-COOH). They are known for their acidic properties due to the ability to donate a proton (H+) from the hydroxyl part of the carboxyl group. In the context of the reaction with diazomethane, the carboxylic acid acts as the starting material that will be converted into an ester.
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Carboxylic Acids Nomenclature
Diazomethane
Diazomethane (CH2N2) is a highly reactive compound used in organic synthesis, particularly for methylation reactions. It contains a diazo group, which makes it a good methylating agent. In the proposed reaction, diazomethane reacts with the carboxylic acid to form a methyl ester, releasing nitrogen gas (N2) as a byproduct.
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Esterification Mechanism
The esterification mechanism involves the nucleophilic attack of the diazomethane on the carbonyl carbon of the carboxylic acid. This process typically includes the formation of a tetrahedral intermediate, followed by the elimination of water and the formation of the ester bond. Understanding this mechanism is crucial for proposing a detailed reaction pathway for the conversion of carboxylic acids to esters using diazomethane.
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