Aldehydes, Ketones & Carboxylic Acids

IUPAC names of cyclic ketones

• Cyclic ketones are ketones in which the carbonyl group is part of a ring structure.
• Their names are derived from cycloalkanes, with the suffix “-one” indicating the presence of a ketone functional group.
• The numbering of the carbon atoms in the ring starts from the carbonyl carbon.
• Let’s look at some examples and their IUPAC names.

Example 1: Cyclohexanone

• Cyclohexanone is a cyclic ketone with a six-membered ring.
• The carbonyl group is attached to one of the carbons in the ring.
• The IUPAC name for cyclohexanone is 2-cyclohexanone.

Example 2: Cyclopentanone

• Cyclopentanone is a cyclic ketone with a five-membered ring.
• The carbonyl group is attached to one of the carbons in the ring.
• The IUPAC name for cyclopentanone is 2-cyclopentanone.

Example 3: Cycloheptanone

• Cycloheptanone is a cyclic ketone with a seven-membered ring.
• The carbonyl group is attached to one of the carbons in the ring.
• The IUPAC name for cycloheptanone is 2-cycloheptanone.

Recap:

• Cyclic ketones have the suffix “-one” in their IUPAC names.
• The numbering of the carbon atoms in the ring starts from the carbonyl carbon.
• Examples include cyclohexanone, cyclopentanone, and cycloheptanone.

11. Nomenclature of Aldehydes

• Aldehydes are organic compounds that contain a carbonyl group (C=O) at the end of a carbon chain.
• The carbonyl carbon is always assigned the number 1, and the other atoms are numbered accordingly.
• The parent hydrocarbon chain is named using the appropriate prefix (meth-, eth-, prop-, etc.), followed by the suffix “-al” for aldehydes.
• Examples:
  • Formaldehyde (methanal): The simplest aldehyde with the structure HCHO.
  • Acetaldehyde (ethanal): An aldehyde with the structure CH3CHO.

12. Nomenclature of Ketones

• Ketones are organic compounds that contain a carbonyl group (C=O) bonded to two carbon atoms.
• The longest carbon chain that includes the ketone group is selected as the parent chain.
• The parent chain is named using the appropriate prefix (meth-, eth-, prop-, etc.), followed by the suffix “-one” for ketones.
• The carbon atoms attached to the carbonyl group are numbered to give the lowest possible combination.
• Examples:
  • Acetone (propanone): The simplest ketone with the structure CH3COCH3.
  • Butanone: A ketone with the structure CH3COCH2CH3.

13. Nomenclature of Carboxylic Acids

• Carboxylic acids are organic compounds that contain a carboxyl group (COOH).
• The carboxyl carbon is assigned the number 1, and other atoms are numbered accordingly.
• The parent hydrocarbon chain is named using the appropriate prefix (meth-, eth-, prop-, etc.), followed by the suffix “-oic acid” for carboxylic acids.
• Examples:
  • Formic acid (methanoic acid): The simplest carboxylic acid with the structure HCOOH.
  • Acetic acid (ethanoic acid): A carboxylic acid with the structure CH3COOH.

14. Physical Properties of Aldehydes

• Aldehydes have higher boiling points compared to alkanes and ethers due to the presence of the polar carbonyl group.
• The boiling points increase with an increase in molecular weight.
• Aldehydes have distinctive odors and are often used as fragrances or flavoring agents.
• Aldehydes are generally soluble in water and have higher solubilities than corresponding ketones.

15. Chemical Reactions of Aldehydes

• Aldehydes can undergo oxidation reactions to form carboxylic acids.
• They react with primary amines to form imines (Schiff bases).
• Aldehydes can be reduced to primary alcohols using reducing agents like NaBH4.
• Aldehydes also undergo nucleophilic addition reactions with nucleophiles like HCN and Grignard reagents.

16. Physical Properties of Ketones

• Ketones have higher boiling points compared to alkanes and ethers due to the presence of the polar carbonyl group.
• The boiling points increase with an increase in molecular weight.
• Ketones have distinct odors and are often used as solvents and flavoring agents.
• Ketones are generally soluble in water, especially those with smaller carbon chains.

17. Chemical Reactions of Ketones

• Ketones can undergo oxidation reactions to form carboxylic acids. However, ketones themselves are resistant to further oxidation.
• They react with secondary amines to form enamines.
• Ketones can be reduced to secondary alcohols using reducing agents like NaBH4.
• Ketones also undergo nucleophilic addition reactions with nucleophiles like HCN and Grignard reagents.

18. Physical Properties of Carboxylic Acids

• Carboxylic acids have higher boiling points compared to alcohols, aldehydes, and ketones due to the presence of the polar carboxyl group.
• The boiling points increase with an increase in molecular weight.
• Carboxylic acids have distinctive odors and are often responsible for the sour taste of fruits and vinegar.
• Carboxylic acids are generally soluble in water, forming hydrogen bonds with water molecules.

19. Chemical Reactions of Carboxylic Acids

• Carboxylic acids can undergo esterification reactions with alcohols to form esters.
• They react with bases to form carboxylate salts.
• Carboxylic acids can be decarboxylated to form carbon dioxide and a hydrocarbon.
• Carboxylic acids also undergo oxidation reactions to form carbon dioxide and water.

20. Distinguishing Tests

• Tollens’ Test: Aldehydes can be identified by their ability to reduce Tollens’ reagent (ammoniacal silver nitrate), forming a silver mirror.
• Fehling’s Test: Aldehydes can reduce Fehling’s solution (a mixture of copper sulfate and sodium hydroxide), forming a red precipitate of copper(I) oxide.
• Iodoform Test: Methyl ketones (ketones with a methyl group adjacent to the carbonyl group) can be identified by their ability to produce a yellow precipitate of iodoform when treated with iodine and a base.
• These tests can help differentiate between aldehydes, ketones, and other functional groups.

21. Properties of Cyclic Ketones

• Cyclic ketones have higher boiling points compared to their corresponding linear counterparts.
• The presence of a ring structure increases the molecular weight, leading to stronger intermolecular forces.
• Cyclic ketones tend to have higher stabilities compared to linear ketones.
• They exhibit similar reactivity as other ketones due to the presence of the carbonyl group.
• Cyclic ketones can undergo nucleophilic addition reactions, oxidation reactions, and reduction reactions.

22. Preparation of Cyclic Ketones

• Cyclic ketones can be prepared through various methods:
  • From the oxidation of cyclic secondary alcohols using oxidizing agents such as Jones reagent or chromic acid.
  • From the reaction of cyclic primary alcohols with acid anhydrides or acid chlorides in the presence of a Lewis acid catalyst.
  • From the oxidative cleavage of cyclic alkenes followed by a tautomerization process.

23. Reactions of Cyclic Ketones

• Cyclic ketones can undergo a wide range of reactions, including:
  • Reduction to form cyclic secondary alcohols using reducing agents like sodium borohydride (NaBH4) or lithium aluminum hydride (LiAlH4).
  • Oxidation to form ring-opening products with the formation of carboxylic acids.
  • Nucleophilic addition reactions with nucleophiles such as Grignard reagents or primary alkylamines.
  • Ring expansion reactions to form larger cyclic ketones or lactones.

24. Examples of Cyclic Ketones

• Camphor: A cyclic ketone with the structure C10H16O.
• Pulegone: A cyclic ketone commonly found in essential oils with the structure C10H16O.
• Cyclohexanedione: A cyclic ketone with a 6-membered ring and two carbonyl groups.
• Levulinic acid: A cyclic ketone that can be hydrolyzed to form a carboxylic acid.

25. Applications of Cyclic Ketones

• Cyclic ketones have various applications in different industries, including:
  • Fragrance and flavor industry: Many cyclic ketones are used as fragrances or flavoring agents due to their pleasant odors.
  • Pharmaceutical industry: Cyclic ketones can serve as building blocks for the synthesis of pharmaceutical compounds.
  • Polymer industry: Some cyclic ketones are used in the production of polymers, such as cyclohexanone used in the production of nylon.

26. Structure and Naming of Aldehydes

• Aldehydes have a carbonyl group (C=O) at the end of a carbon chain.
• The carbonyl carbon is always assigned the number 1, and the other atoms are numbered accordingly.
• Aldehydes are named by replacing the “-e” ending of the corresponding alkane with the suffix “-al”.
• Examples: Ethanal (acetaldehyde), Propanal, Butanal.

27. Preparation of Aldehydes

• Aldehydes can be prepared through various methods:
  • From the oxidation of primary alcohols using oxidizing agents such as acidic potassium dichromate (K2Cr2O7) or PCC (pyridinium chlorochromate).
  • From the reduction of acyl chlorides (acid chlorides) using reducing agents like sodium borohydride (NaBH4) or lithium aluminum hydride (LiAlH4).
  • From the oxidation of alkynes using ozonolysis followed by reductive workup.

28. Reactions of Aldehydes

• Aldehydes can undergo various reactions, including:
  • Oxidation to form carboxylic acids using strong oxidizing agents like potassium permanganate (KMnO4) or chromic acid (H2CrO4).
  • Reduction to form primary alcohols using reducing agents like sodium borohydride (NaBH4) or lithium aluminum hydride (LiAlH4).
  • Nucleophilic addition reactions with nucleophiles such as ammonia, primary amines, and Grignard reagents.
  • Formation of hemiacetals and acetals through reactions with alcohols.

29. Structure and Naming of Ketones

• Ketones have a carbonyl group (C=O) bonded to two carbon atoms.
• The longest carbon chain that includes the carbonyl group is selected as the parent chain.
• Ketones are named by replacing the “-e” ending of the corresponding alkane with the suffix “-one”.
• The carbonyl carbon is always assigned the lowest possible number.
• Examples: Propanone (acetone), Butanone, Pentan-3-one.

30. Preparation of Ketones

• Ketones can be prepared through various methods:
  • From the oxidation of secondary alcohols using oxidizing agents such as chromic acid (H2CrO4) or potassium permanganate (KMnO4).
  • From the oxidation of alkyl benzyl ethers using peroxyacids like m-chloroperoxybenzoic acid (m-CPBA).
  • From the oxidative cleavage of alkenes followed by hydration of the resulting carbonyl compound.
  • From the reaction of acid chlorides with secondary alkyl or aryl organometallic reagents.