Textbook Question
Show what esters would undergo Claisen condensation to give the following β-keto esters.
(c)
25. Condensation Chemistry
Claisen Condensation
4:34 minutesProblem 34
Textbook Question
Ethoxide is used as the base in the condensation of ethyl acetate to avoid some unwanted side reactions. Show what side reactions would occur if the following bases were used.
(a) sodium methoxide
(b) sodium hydroxide
Verified step by step guidance1
Step 1: Understand the role of the base in the condensation of ethyl acetate. Ethoxide is used because it matches the ethyl group in ethyl acetate, minimizing the risk of transesterification or other side reactions.
Step 2: Analyze the potential side reactions with sodium methoxide (CH₃O⁻). Sodium methoxide introduces a methyl group, which can lead to transesterification. This reaction would replace the ethyl group in ethyl acetate with a methyl group, forming methyl acetate (CH₃COOCH₃).
Step 3: Write the transesterification reaction for sodium methoxide: \( \text{CH₃CH₂COOCH₂CH₃} + \text{CH₃O⁻} \rightarrow \text{CH₃COOCH₃} + \text{CH₃CH₂O⁻} \). This shows the exchange of the ethyl group with a methyl group.
Step 4: Analyze the potential side reactions with sodium hydroxide (NaOH). Sodium hydroxide is a strong base and can cause hydrolysis of ethyl acetate, leading to the formation of ethanol (CH₃CH₂OH) and acetate ion (CH₃COO⁻).
Step 5: Write the hydrolysis reaction for sodium hydroxide: \( \text{CH₃CH₂COOCH₂CH₃} + \text{OH⁻} \rightarrow \text{CH₃COO⁻} + \text{CH₃CH₂OH} \). This reaction breaks the ester bond, producing an alcohol and a carboxylate ion.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Base Strength and Reactivity
Different bases have varying strengths and reactivities, which influence the types of reactions they can facilitate. Sodium methoxide is a stronger base than sodium hydroxide, making it more likely to deprotonate substrates and lead to side reactions. Understanding the strength of a base helps predict its behavior in organic reactions, particularly in condensation processes.
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Side Reactions in Organic Chemistry
Side reactions are unintended reactions that can occur alongside the desired reaction, often leading to byproducts. In the case of using sodium methoxide or sodium hydroxide, these bases can promote hydrolysis or elimination reactions, which can interfere with the main condensation reaction of ethyl acetate. Recognizing potential side reactions is crucial for optimizing reaction conditions.
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Condensation Reactions
Condensation reactions involve the combination of two molecules with the loss of a small molecule, often water. In the context of ethyl acetate, the condensation reaction typically aims to form a larger molecule while eliminating a byproduct. The choice of base can significantly affect the efficiency and selectivity of the condensation, making it essential to choose a base that minimizes side reactions.
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