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Questions and Answers
What is the term used to describe the rapid interconversion between a keto compound and its enol isomer at equilibrium?
What is the term used to describe the rapid interconversion between a keto compound and its enol isomer at equilibrium?
Which functional group is involved in keto-enol tautomerism?
Which functional group is involved in keto-enol tautomerism?
In keto-enol tautomerism, what catalyzes the conversion between the keto and enol forms?
In keto-enol tautomerism, what catalyzes the conversion between the keto and enol forms?
Which type of compounds are tautomers of each other?
Which type of compounds are tautomers of each other?
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What type of reaction is the Claisen condensation?
What type of reaction is the Claisen condensation?
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Which compound is formed in the Acetoacetic ester synthesis reaction?
Which compound is formed in the Acetoacetic ester synthesis reaction?
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What is the role of a strong base in the Acetoacetic ester synthesis?
What is the role of a strong base in the Acetoacetic ester synthesis?
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Which halides work best in Acetoacetic ester synthesis?
Which halides work best in Acetoacetic ester synthesis?
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What kind of atom on a compound rapidly equilibrates with its corresponding enol isomer in keto-enol tautomerism?
What kind of atom on a compound rapidly equilibrates with its corresponding enol isomer in keto-enol tautomerism?
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In keto-enol tautomerism, what term describes compounds that differ only in the position of protons and electrons?
In keto-enol tautomerism, what term describes compounds that differ only in the position of protons and electrons?
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Study Notes
Dicarboxylic Acids
- Dicarboxylic acids (also called diacids) are organic compounds that contain two carboxylic acid (-CO2H) functional groups.
- Their general molecular formula is written as HO2C-RCO2H, where R can be an aliphatic or aromatic.
- Examples include oxalic, malonic, and isophthalmic acids.
- Amino acids, such as aspartic and glutamic acids, are also dicarboxylic acids.
Naming of Dicarboxylic Acids
- Dicarboxylic acids are 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".
Physical Properties
- Dicarboxylic acids are colorless and odorless crystalline substances at room temperature.
- They have higher melting points than those of monocarboxylic acids containing the same number of carbon atoms.
Reactions
- Thermal reactivity: Dicarboxylic acids react differently depending on the chain length separating the carboxyl groups.
- Condensation reaction: Dicarboxylic acids react with amines to form cyclic imides.
- Polymerization reaction: Dicarboxylic acids are used to produce high-performance polymers (polyesters, polyamides), anti-corrosives, etc.
Thermal Reactivity
- Ring formation is usually favored if a 5- or 6-membered ring can be formed.
- Diacids with carboxylic groups at positions 1 and 6 or 7 when heated, decarboxylate to form cyclic ketones.
- Diacids with carboxylic groups at positions 1 and 4 or 5 when heated, dehydrate to form a cyclic acid anhydride.
- Dicarboxylic acids with short carbon chains when heated, decompose to form carbon dioxide and a monocarboxylic acid.
Reactions with Amines
- Dicarboxylic acids react with amines to form cyclic imides.
Condensation
- Esters of most dicarboxylic acids, except propanedioic esters, undergo an intramolecular Claisen condensation to form a 5- or 6-membered cyclic β-keto esters.
Polymerization
- Dicarboxylic acids are used to produce high-performance polymers (polyesters, polyamides), anti-corrosives, etc.
- An example is adipic acid used in the preparation of nylon.
Keto Acids
- β-keto acids have the ketone group at the second carbon from the carboxylic acid.
- An example is acetoacetic acid, a weak β-keto acid produced from acetyl-CoA in the mitochondria of hepatocytes.
- γ-keto acids have the ketone group at the third carbon from the carboxylic acid.
- An example is levulinic acid, used as a precursor for some pharmaceutical agents and in cosmetics.
Keto Esters
- Keto esters are organic compounds that contain an ester and a ketone functional groups.
- A type of keto esters is β-keto esters in which the carbonyl functional group is attached to a β-carbon.
Claisen Condensation
- Claisen condensation is 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.
- The reaction takes place only in nonaqueous bases such as sodium ethoxide because aqueous bases such as NaOH lead to hydrolysis of the 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.
- Keto-enol tautomerism is catalyzed by either an acid or a base.
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Test your knowledge on dicarboxylic acids, organic compounds with two carboxylic acid functional groups. Explore examples like oxalic, malonic, and isophthalic acids in this quiz.
