UDS-SPPS Pharmaceutical Chemistry: Dicarboxylic Acids Lecture Quiz

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.