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Questions and Answers
What is the purpose of the acetoacetic ester synthesis reaction?
To form a methyl ketone
What occurs during the enolate ion formation step in the acetoacetic ester synthesis?
A strong base deprotonates the dicarbonyl α-carbon
How is the enolate of ethyl acetoacetate formed?
By treatment with sodium ethoxide in ethanol
What type of reaction leads to alkylation at the α-carbon in acetoacetic ester synthesis?
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What happens when the alkylated acetoacetic ester is heated with aqueous HCl?
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What product is obtained when ethyl acetoacetate reacts with 1-bromoethane followed by hydrolysis and decarboxylation?
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What type of alkyl halides do not undergo substitution reactions in acetoacetic ester synthesis?
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What is the final product of the acetoacetic ester synthesis reaction sequence?
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Which step involves the nucleophilic substitution of an alkyl halide in acetoacetic ester synthesis?
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Describe the mechanism of ethyl acetoacetate conversion to 2-pentanone in acetoacetic ester synthesis.
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Study Notes
Dicarboxylic Acids
- Organic compounds that contain two carboxylic acid (-CO2H) functional groups
- General molecular formula: HO2C-RCO2H, where R can be an aliphatic or aromatic
- Examples: oxalic, malonic, and isophthalic acids, as well as amino acids aspartic and glutamic acids
Naming of Dicarboxylic Acids
- Named by adding the suffix "dioic" acid to the name of the carbon chain that contains both carboxyl groups
- Aliphatic dicarboxylic acids with a cycloalkane ring are named by giving the name of the ring and adding the suffix -dicarboxylic acid
- Aromatic dicarboxylic acids are named by adding the words "dicarboxylic acid" to "benzene"
Dicarboxylic Acids: Physical Properties
- Colorless and odorless crystalline substances at room temperature
- Enolate anion of diethyl malonate is a nucleophile and reacts by an SN2 pathway with methyl and primary haloalkanes, α-haloketones, and α-haloesters
Dicarboxylic Acids: Malonic Ester Synthesis
- Malonic ester is a β-diester with a methylene (CH2) group bonded between two carbonyl groups
- Diethyl malonate is converted to its enolate ion by reaction with NaOEt in ethanol, which then reacts rapidly with an alkyl halide to give an α-substituted malonic ester
- On heating with aqueous HCl acid, the alkylated malonic ester undergoes hydrolysis of its two ester groups followed by decarboxylation to yield a substituted monocarboxylic acid
Keto Acids and Esters
- Keto acids (also called oxo acids) are organic compounds that contain a carboxylic acid and ketone functional groups
- Examples: pyruvic acid, acetoacetic acid, and levulinic acid
Types of Keto Acids
- α-keto acids have the keto group adjacent to the carboxylic acid
- Examples: pyruvic acid, oxaloacetic acid, and α-ketoglutaric acid
- β-keto acids have the ketone group at the second carbon from the carboxylic acid
- Example: acetoacetic acid
- γ-keto acids have the ketone group at the third carbon from the carboxylic acid
- Example: levulinic acid
Keto Esters
- Organic compounds that contain an ester and a ketone functional groups
- Example: β-keto esters, which have the carbonyl functional group attached to a β-carbon
Claisen Condensation
- A carbonyl condensation reaction between two esters in the presence of a strong base to form a β-keto ester
- The Claisen condensation is the main method for preparing β-keto esters
- Reaction mechanism involves the formation of an enolate ion, which reacts with an ester to form a β-keto ester
Keto-Enol Tautomerism
- A carbonyl compound with a hydrogen atom on its α-carbon rapidly equilibrates with its corresponding enol isomer
- The rapid interconversion between a keto compound and its enol isomer at equilibrium via intramolecular rearrangement of protons and electrons is called keto-enol tautomerism
- Tautomers are constitutional isomers of a compound, which differ only in the position of protons and electrons
Acetoacetic Ester Synthesis
- A chemical reaction where an ethyl acetoacetate reacts with an alkyl halide in the presence of a strong base to form a methyl ketone
- Reaction mechanism involves a 3-step sequence of: enolate ion formation, alkylation, and hydrolysis/decarboxylation
- Examples: ethyl acetoacetate reacts with 1-bromoethane in the presence of NaOEt followed by hydrolysis and decarboxylation to form 2-pentanone
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Description
Test your knowledge on dicarboxylic acids, organic compounds containing two carboxylic acid functional groups with the general molecular formula HO2C-RCO2H. Explore examples like oxalic, malonic, and isophthalic acids.
