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Questions and Answers
What is the purpose of the acetoacetic ester synthesis reaction?
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?
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?
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?
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?
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?
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?
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?
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?
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.
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.
