Textbook Question
Show how crossed Claisen condensations could be used to prepare the following esters.
(b)
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Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
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Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 42a,b
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 42a,bChapter 22, Problem 42a,b
Predict the products from crossed Claisen condensation of the following pairs of esters. Indicate which combinations are poor choices for crossed Claisen condensations.
(a) 
(b) 
Verified step by step guidance1
Step 1: Understand the Claisen condensation reaction. It involves the reaction of two esters in the presence of a strong base to form a β-keto ester or a β-diketone. Crossed Claisen condensation refers to the reaction between two different esters.
Step 2: Identify the esters involved in the reaction. Examine the structures provided in the images for both parts (a) and (b). Note the alkyl groups attached to the ester functional groups.
Step 3: Consider the reactivity of the esters. Esters with α-hydrogens are more reactive in Claisen condensations because they can form enolates. Determine which esters have α-hydrogens available for enolate formation.
Step 4: Predict the products. The enolate formed from one ester will attack the carbonyl carbon of the other ester, leading to the formation of a new carbon-carbon bond. Write the structure of the expected β-keto ester or β-diketone product for each pair of esters.
Step 5: Evaluate the suitability of the ester pairs for crossed Claisen condensation. Poor choices typically involve esters that lack α-hydrogens or have steric hindrance that prevents effective enolate formation or attack. Indicate which combinations are less favorable based on these criteria.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Claisen Condensation
Claisen condensation is a reaction between two esters or an ester and a carbonyl compound in the presence of a strong base, leading to the formation of a β-keto ester or a β-diketone. This reaction involves the nucleophilic attack of an enolate ion derived from one ester on the carbonyl carbon of another, resulting in a new carbon-carbon bond. Understanding this mechanism is crucial for predicting the products of crossed Claisen condensations.
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Claisen Condensation
Enolate Ion Formation
Enolate ions are formed when a strong base abstracts a proton from the α-carbon of an ester, creating a resonance-stabilized anion. This enolate can act as a nucleophile in Claisen condensation reactions. The stability of the enolate ion is influenced by the structure of the ester, making it essential to identify which esters can effectively generate enolates for successful crossed Claisen reactions.
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Crossed Claisen Condensation
Crossed Claisen condensation involves the reaction of two different esters, which can lead to multiple products depending on the reactivity of the esters involved. Some combinations may yield poor results due to the possibility of self-condensation or the formation of unreactive enolates. Identifying which ester pairs are likely to react favorably is key to predicting the products and understanding the limitations of this reaction.
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Related Practice
Textbook Question
Some (but not all) of the following keto esters can be formed by Dieckmann condensations. Determine which ones are possible, and draw the starting diesters.
(c)
(d)
1298
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Textbook Question
Some (but not all) of the following keto esters can be formed by Dieckmann condensations. Determine which ones are possible, and draw the starting diesters.
(a)
(b)
963
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Textbook Question
Propose a mechanism for the crossed Claisen condensation between ethyl acetate and ethyl benzoate.
115
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Textbook Question
Predict the products from crossed Claisen condensation of the following pairs of esters. Indicate which combinations are poor choices for crossed Claisen condensations.
(c)
(d)
709
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Textbook Question
Show how crossed Claisen condensations could be used to prepare the following esters.
(a)
1001
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