Aldehydes, Ketones & Carboxylic Acids

  • IUPAC names of open chain ketones “Slide 2”

IUPAC Nomenclature for Ketones

  • Ketones are organic compounds with a carbonyl group (C=O) bonded to two alkyl or aryl groups.
  • The IUPAC nomenclature system is used to name ketones based on the longest carbon chain that includes the carbonyl group.
  • The parent chain is numbered starting from the end closer to the carbonyl group.
  • The suffix “-one” is used in the name to indicate the presence of a ketone functional group. “Slide 3”

Naming Ketones Example 1

Structure: O | R₁ ─ C ─ R₂ IUPAC Name:

  • Select the longest carbon chain that includes the carbonyl group, considering the substituent groups attached to it.
  • Number the parent chain to give the carbonyl carbon the lowest possible number.
  • Replace the suffix of the alkane’s name with “-one.” Example: O | CH₃ ─ C ─ CH₂ ─ CH₃ IUPAC Name: Propanone “Slide 4”

Naming Ketones Example 2

Structure: O || R₁ ─ C ─ R₂ IUPAC Name:

  • Select the longest carbon chain that includes the carbonyl group, considering the substituent groups attached to it.
  • Number the parent chain to give the carbonyl carbon the lowest possible number.
  • Replace the suffix of the alkane’s name with “-one.”
  • If there are additional substituents, name them as prefixes with appropriate locants. Example: O || CH₃ ─ C ─ CH₂ ─ CH₂ ─ CH₃ IUPAC Name: 4-Methylpentan-2-one “Slide 5”

Naming Ketones Example 3

Structure: O || R₁ ─ C ─ C ─ R₂ IUPAC Name:

  • Select the longest carbon chain that includes the carbonyl group, considering the substituent groups attached to it.
  • Number the parent chain to give the carbonyl carbon the lowest possible number.
  • Replace the suffix of the alkane’s name with “-one.”
  • If there are additional substituents, name them as prefixes with appropriate locants. Example: O || CH₃ ─ C ─ C ─ CH₂ ─ CH₃ IUPAC Name: 2-Methylbutan-3-one “Slide 6”

Naming Ketones Example 4

Structure: O || R₁ ─ C ─ C ─ C ─ R₂ IUPAC Name:

  • Select the longest carbon chain that includes the carbonyl group, considering the substituent groups attached to it.
  • Number the parent chain to give the carbonyl carbon the lowest possible number.
  • Replace the suffix of the alkane’s name with “-one.”
  • If there are additional substituents, name them as prefixes with appropriate locants. Example: O || CH₃ ─ C ─ C ─ C ─ CH₂ ─ CH₃ IUPAC Name: 2-Ethylpentan-3-one “Slide 7”

Summary

  • Ketones are organic compounds with a carbonyl group bonded to two alkyl or aryl groups.
  • The IUPAC nomenclature system is used to name ketones based on the longest carbon chain that includes the carbonyl group.
  • The suffix “-one” is used in the name to indicate the presence of a ketone functional group.
  • When naming ketones, number the parent chain to give the carbonyl carbon the lowest possible number.
  • Additional substituents are named as prefixes with appropriate locants. “Slide 8”

Recap

  • Ketones have a carbonyl group (C=O) bonded to two alkyl or aryl groups.
  • IUPAC nomenclature is used to name ketones based on the longest carbon chain including the carbonyl group.
  • Number the parent chain to give the carbonyl carbon the lowest possible number.
  • Replace the suffix of the alkane’s name with “-one.”
  • Additional substituents are named as prefixes with appropriate locants. “Slide 9”

Practice Questions

  1. What is the IUPAC name of the ketone shown below? O | CH₃ ─ C ─ CH₂ ─ CH₂ ─ CH₃
  1. Name the following ketone using IUPAC nomenclature: O | CH₃ ─ C ─ CH₂ ─ CH₂ ─ CH₂ ─ CH₃
  1. Identify the ketone from the given structures and provide the IUPAC name:
    • CH₃ ─ C ─ CH₂ ─ C(CH₃)₂ ─ CH₂CH₃
    • CH₃CH₂C(CH₃)₂CH₂C(CH₃)₃ “Slide 10”

Answers:

  1. IUPAC Name: 4-Methylpentan-2-one
  1. IUPAC Name: Hexan-3-one
  1. IUPAC Names:
    • CH₃ ─ C ─ CH₂ ─ C(CH₃)₂ ─ CH₂CH₃ - 4-Ethyl-2,4-dimethylpentan-3-one
    • CH₃CH₂C(CH₃)₂CH₂C(CH₃)₃ - 3,5,5-Trimethylheptan-2-one Slide 11

Aldehydes, Ketones & Carboxylic Acids

  • Aldehydes, ketones, and carboxylic acids are organic compounds that contain a carbonyl group (C=O).
  • The carbonyl group consists of a carbon atom attached to an oxygen atom by a double bond.
  • The position of the carbonyl group in the molecule determines whether it is an aldehyde, ketone, or carboxylic acid. Slide 12

Aldehydes

  • Aldehydes have the carbonyl group (C=O) at the terminal carbon of the carbon chain.
  • Aldehydes are named by replacing the “-e” ending of the corresponding alkane with “-al.”
  • The aldehyde functional group is represented by -CHO. Examples:
  • Methanal (formaldehyde): HCHO
  • Ethanal (acetaldehyde): CH₃CHO Slide 13

Ketones

  • Ketones have the carbonyl group (C=O) positioned at a non-terminal carbon of the carbon chain.
  • Ketones are named by replacing the “-e” ending of the corresponding alkane with “-one.”
  • The ketone functional group is represented by -C(O)-. Examples:
  • Propanone (acetone): CH₃COCH₃
  • Butan-2-one (methyl ethyl ketone): CH₃COCH₂CH₃ Slide 14

Carboxylic Acids

  • Carboxylic acids have the carbonyl group (C=O) positioned at the terminal carbon of the carbon chain, with a hydroxyl group (-OH) attached to the same carbon.
  • Carboxylic acids are named by replacing the “-e” ending of the corresponding alkane with “-oic acid.”
  • The carboxylic acid functional group is represented by -COOH. Examples:
  • Methanoic acid (formic acid): HCOOH
  • Ethanoic acid (acetic acid): CH₃COOH Slide 15

Nomenclature Examples

  1. Aldehyde:
    • Structure: HCHO
    • IUPAC Name: Methanal
  1. Ketone:
    • Structure: CH₃COCH₃
    • IUPAC Name: Propanone
  1. Carboxylic Acid:
    • Structure: CH₃CH₂COOH
    • IUPAC Name: Ethanoic acid Slide 16

Oxidation Reactions

  • Aldehydes can be oxidized to carboxylic acids using a strong oxidizing agent such as potassium permanganate (KMnO₄) or acidified potassium dichromate (K₂Cr₂O₇).
    • Aldehyde → Carboxylic Acid Example:
  • Ethanal (CH₃CHO) can be oxidized to ethanoic acid (CH₃COOH). Slide 17

Reduction Reactions

  • Aldehydes and ketones can be reduced to primary and secondary alcohols, respectively.
    • Aldehyde → Primary Alcohol
    • Ketone → Secondary Alcohol Example:
  • Ethanal (CH₃CHO) can be reduced to ethanol (CH₃CH₂OH).
  • Propanone (CH₃COCH₃) can be reduced to propan-2-ol (CH₃CH(OH)CH₃). Slide 18

Addition Reactions

  • Aldehydes and ketones undergo addition reactions with nucleophiles to form new functional groups.
    • Nucleophile + Aldehyde/Ketone → Addition Product Example:
  • Reaction with HCN (hydrocyanation):
    • Aldehyde/Ketone + HCN → Cyanohydrin Slide 19

Polymerization of Aldehydes and Ketones

  • Aldehydes and ketones can undergo condensation polymerization to form polymers called resins.
  • The polymerization reaction involves the combination of carbonyl groups to form larger macromolecules. Example:
  • The polymerization of formaldehyde (methanal) results in the formation of a resin called Bakelite. Slide 20

Summary

  • Aldehydes, ketones, and carboxylic acids are organic compounds containing a carbonyl group (C=O).
  • Aldehydes have the carbonyl group at the terminal carbon, ketones at a non-terminal carbon, and carboxylic acids at the terminal carbon with a hydroxyl group attached.
  • Naming is based on replacing the suffix of the corresponding alkane with “-al” for aldehydes, “-one” for ketones, and “-oic acid” for carboxylic acids.
  • Aldehydes can be oxidized to carboxylic acids, while aldehydes and ketones can be reduced to alcohols.
  • Addition reactions and condensation polymerization are common reactions of aldehydes and ketones. Slide 21

Reactions of Aldehydes

  • Aldehydes can undergo a variety of reactions due to the presence of the carbonyl group.
  • Some common reactions of aldehydes include:
    1. Oxidation reactions
    2. Reduction reactions
    3. Nucleophilic addition reactions Slide 22

Oxidation of Aldehydes

  • Aldehydes can be oxidized to carboxylic acids using strong oxidizing agents.
  • Oxidizing agents include potassium dichromate (K₂Cr₂O₇) and potassium permanganate (KMnO₄).
  • The carbonyl group of the aldehyde is converted into a carboxyl group (COOH) during oxidation. Slide 23

Reduction of Aldehydes

  • Aldehydes can be reduced to primary alcohols.
  • A common reducing agent for aldehydes is sodium borohydride (NaBH₄).
  • The carbonyl group of the aldehyde is converted into a hydroxyl group (-OH) during reduction. Slide 24

Nucleophilic Addition Reactions of Aldehydes

  • Aldehydes can undergo nucleophilic addition reactions with various nucleophiles.
  • Nucleophiles attack the electrophilic carbon of the carbonyl group, leading to the formation of new bonds.
  • Examples of nucleophiles include water, alcohols, amines, and cyanide ions. Slide 25

Nucleophilic Addition of Water (Hydration)

  • Aldehydes can react with water in the presence of an acid catalyst to form hydrates.
  • Hydrates are compounds where a water molecule adds to the carbonyl group.
  • The reaction is reversible, and the equilibrium between the aldehyde and its hydrate is established. Slide 26

Nucleophilic Addition of Alcohols (Acetal Formation)

  • Aldehydes can react with alcohols in the presence of an acid catalyst to form acetals.
  • Acetals are derivatives of aldehydes where two -OR groups are attached to the carbonyl carbon.
  • The reaction is reversible, and the equilibrium between the aldehyde and its acetal is established. Slide 27

Nucleophilic Addition of Amines (Imine Formation)

  • Aldehydes can react with primary amines to form imines.
  • An imine is a nitrogen-containing compound where the nitrogen atom bonds to the carbonyl carbon.
  • The reaction is reversible, and the equilibrium between the aldehyde and its imine is established. Slide 28

Nucleophilic Addition of Cyanide Ions (Cyanohydrin Formation)

  • Aldehydes can react with cyanide ions (CN-) to form cyanohydrins.
  • A cyanohydrin is a compound where a cyano group (-CN) is attached to the carbonyl carbon.
  • The reaction is reversible, and the equilibrium between the aldehyde and its cyanohydrin is established. Slide 29

Examples of Aldehyde Reactions

  1. Oxidation reaction:
    • Formaldehyde (HCHO) can be oxidized to formic acid (HCOOH) using an oxidizing agent such as potassium permanganate.
  1. Reduction reaction:
    • Propanal (CH₃CH₂CHO) can be reduced to propan-1-ol (CH₃CH₂CH₂OH) using a reducing agent such as sodium borohydride. Slide 30

Recap

  • Aldehydes can undergo different types of reactions due to the presence of the carbonyl group.
  • Oxidation of aldehydes converts them into carboxylic acids.
  • Reduction of aldehydes converts them into primary alcohols.
  • Nucleophilic addition reactions involve the attack of nucleophiles on the carbonyl carbon, leading to the formation of hydrates, acetals, imines, or cyanohydrins.
  • Examples include oxidation of formaldehyde to formic acid and reduction of propanal to propan-1-ol.