Textbook Question
Predict the major products of the following crossed Claisen condensations.
(c)
2
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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 43c,d
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 43c,dChapter 22, Problem 43c,d
Show how crossed Claisen condensations could be used to prepare the following esters.
(c) 
(d) 
Verified step by step guidance1
Step 1: Understand the crossed Claisen condensation reaction. This reaction involves two different esters or an ester and a ketone reacting in the presence of a strong base (such as alkoxide) to form a β-keto ester. The reaction requires one of the reactants to lack α-hydrogens to prevent self-condensation.
Step 2: Analyze the target ester structure. For part (c), the ester contains a phenyl group (Ph) attached to the α-carbon and two ester groups. For part (d), the ester contains a tert-butyl group ((CH₃)₃C) and a butyl group (CH₂CH₂CH₃) attached to the α-carbon along with two ester groups.
Step 3: Identify the starting materials for part (c). To synthesize the ester in part (c), use ethyl benzoate (PhCOOEt) as the ester lacking α-hydrogens and ethyl acetate (CH₃COOEt) as the ester with α-hydrogens. The ethoxide base will deprotonate the α-hydrogens of ethyl acetate, enabling nucleophilic attack on the carbonyl carbon of ethyl benzoate.
Step 4: Identify the starting materials for part (d). To synthesize the ester in part (d), use methyl tert-butylacetate ((CH₃)₃CCOOCH₃) as the ester lacking α-hydrogens and methyl butyrate (CH₃CH₂CH₂COOCH₃) as the ester with α-hydrogens. The methoxide base will deprotonate the α-hydrogens of methyl butyrate, enabling nucleophilic attack on the carbonyl carbon of methyl tert-butylacetate.
Step 5: Write the mechanism for the reaction. For both parts (c) and (d), the mechanism involves: (a) deprotonation of the α-hydrogens of the ester with α-hydrogens, (b) nucleophilic attack of the enolate ion on the carbonyl carbon of the ester lacking α-hydrogens, (c) formation of a tetrahedral intermediate, and (d) elimination of the alkoxide group to form the β-keto ester product.
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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 on the carbonyl carbon of another ester, followed by the elimination of an alcohol. Understanding this mechanism is crucial for predicting the products of crossed Claisen condensations.
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Claisen Condensation
Crossed Claisen Condensation
Crossed Claisen condensation refers to a variation of the Claisen reaction where two different esters or an ester and a carbonyl compound react. This method allows for the synthesis of diverse products, but it requires careful selection of reactants to avoid unwanted side reactions. The ability to control which ester forms the enolate is key to successfully achieving the desired product in this reaction.
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Enolate Ion Formation
Enolate ions are formed when a strong base abstracts a proton from the α-carbon of a carbonyl compound, resulting in a resonance-stabilized anion. This enolate can act as a nucleophile in various reactions, including Claisen condensations. Understanding how to generate and utilize enolate ions is essential for manipulating reaction pathways and achieving specific ester products in crossed Claisen condensations.
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Related Practice
Textbook Question
Predict the major products of the following crossed Claisen condensations.
(b)
10
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Textbook Question
Show how crossed Claisen condensations could be used to prepare the following esters.
(b)
1
views
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)
2
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Textbook Question
Show how crossed Claisen condensations could be used to prepare the following esters.
(a)
1
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Textbook Question
Predict the major products of the following crossed Claisen condensations.
(a)
1
views