Aldehydes, Ketones & Carboxylic Acids

  • Aldehydes, ketones, and carboxylic acids are organic compounds that contain carbonyl functional groups.
  • The carbonyl group consists of a carbon atom bonded to an oxygen atom by a double bond.
  • Aldehydes have the carbonyl group (-CHO) attached to at least one hydrogen atom.
  • Ketones have the carbonyl group (-CO-) attached to two carbon atoms.
  • Carboxylic acids have the carbonyl group (-COOH) attached to a hydroxyl group (-OH).

Nomenclature

  • Aldehydes: Named by replacing the ’e’ ending of the alkane name with ‘-al’.
  • Ketones: Named by replacing the ’e’ ending of the alkane name with ‘-one’.
  • Carboxylic acids: Named by replacing the ’e’ ending of the alkane name with ‘-oic acid’. Example:
  • Aldehyde: Methanal (formaldehyde)
  • Ketone: Propanone (acetone)
  • Carboxylic acid: Ethanoic acid (acetic acid)

Physical Properties

  • Aldehydes and ketones have higher boiling points compared to hydrocarbons of similar molecular weight.
  • This is due to the presence of the polar carbonyl group, which allows for dipole-dipole interactions between molecules.
  • Both aldehydes and ketones are soluble in organic solvents like alcohols and ethers.
  • Carboxylic acids, due to the presence of the -COOH group, can form hydrogen bonds and have higher boiling points than aldehydes and ketones.

Chemical Reactions: Formation of Aldehydes and Ketones

  1. Oxidation of primary alcohols:
    • Primary alcohols can be oxidized to aldehydes using mild oxidizing agents.
    • Further oxidation converts the aldehyde to a carboxylic acid.
    • Example: Primary alcohol → Aldehyde → Carboxylic Acid Oxidation of Primary Alcohol
  1. Oxidation of secondary alcohols:
    • Secondary alcohols are oxidized to ketones using oxidizing agents.
    • Example: Secondary alcohol → Ketone

Chemical Reactions: Reduction of Aldehydes and Ketones

  1. Reduction to primary alcohols:
    • Aldehydes and ketones can be reduced to primary alcohols using reducing agents such as sodium borohydride (NaBH4) or lithium aluminum hydride (LiAlH4).
    • Example: Aldehyde or Ketone → Primary alcohol Reduction of Aldehydes and Ketones
  1. Reduction to secondary alcohols:
    • Ketones can be further reduced to secondary alcohols using strong reducing agents.
    • Example: Ketone → Secondary alcohol

Chemical Reactions: Oxidation of Aldehydes and Ketones

  1. Oxidation to carboxylic acids:
    • Aldehydes can be further oxidized to carboxylic acids using strong oxidizing agents like potassium permanganate (KMnO4) or chromic acid (H2CrO4).
    • Example: Aldehyde → Carboxylic acid Oxidation of Aldehydes and Ketones
  1. No further oxidation of ketones:
    • Ketones do not undergo further oxidation under ordinary laboratory conditions.

Chemical Reactions: Addition Reactions of Aldehydes and Ketones

  1. Addition of hydrogen (reduction):
    • Aldehydes and ketones can undergo reduction by adding hydrogen in the presence of a catalyst like nickel or palladium.
    • Example: Aldehyde or Ketone + Hydrogen → Alcohol
  1. Addition of hydrogen cyanide:
    • Aldehydes and ketones react with hydrogen cyanide (HCN) to form cyanohydrins.
    • Example: Aldehyde or Ketone + HCN → Cyanohydrin

Chemical Reactions: Formation of Oximes and Hydrazones

  1. Reaction with hydroxylamine:
    • Aldehydes and ketones react with hydroxylamine (NH2OH) to form oximes.
    • Example: Aldehyde or Ketone + NH2OH → Oxime
  1. Reaction with hydrazine:
    • Aldehydes and ketones react with hydrazine (N2H4) to form hydrazones.
    • Example: Aldehyde or Ketone + N2H4 → Hydrazone

Chemical Reactions: Esterification of Carboxylic Acids

  • Carboxylic acids react with alcohols in the presence of an acid catalyst to form esters.
  • This reaction is known as esterification.
  • Example: Carboxylic Acid + Alcohol → Ester + Water

That’s all for the first 10 slides. Stay tuned for the next set of slides!

  1. Chemical Reactions: Hydrolysis of Esters
  • Esters can undergo hydrolysis in the presence of water and an acid or base catalyst.
  • Acid-catalyzed hydrolysis:
    • Esters are converted back to carboxylic acids and alcohols.
    • Example: Ester + Water + Acid → Carboxylic Acid + Alcohol
    • This reaction is reversible.
  1. Chemical Reactions: Saponification
  • Saponification is a reaction between an ester and a base, usually hydroxide ions, to produce a carboxylate ion and an alcohol.
  • Example: Ester + Base → Carboxylate ion + Alcohol
  • Saponification is commonly used to produce soaps from fats or oils.
  1. Chemical Reactions: Aldol Condensation
  • Aldol condensation is a reaction between two molecules of an aldehyde or a ketone, resulting in the formation of a β-hydroxyaldehyde or β-hydroxyketone.
  • Example: Aldehyde or Ketone 1 + Aldehyde or Ketone 2 → β-Hydroxyaldehyde or β-Hydroxyketone
  • The reaction involves the formation of an enolate ion followed by nucleophilic addition.
  1. Chemical Reactions: Cannizzaro Reaction
  • The Cannizzaro reaction is a disproportionation reaction of an aldehyde, where one molecule of the aldehyde is oxidized to a carboxylic acid, while another molecule is reduced to a primary alcohol.
  • Examples: Aldehyde 1 + Aldehyde 1 → Carboxylic acid + Alcohol
  1. Chemical Reactions: Haloform Reaction
  • The haloform reaction is a reaction between a methyl ketone and a haloform (CHX3), resulting in the formation of a haloform compound (CX3H).
  • Example: Methyl Ketone + Haloform → Haloform Compound + Carboxylate Ion
  • The reaction proceeds via the oxidation of the methyl group to a carboxylate ion and the reduction of the haloform to a haloform compound.
  1. Chemical Reactions: Reactions of Carboxylic Acids
  • Carboxylic acids undergo various reactions such as:
    • Reaction with metals: Carboxylic acids react with active metals, like sodium or magnesium, to form carboxylate salts and hydrogen gas.
    • Reaction with bases: Carboxylic acids react with bases to form carboxylate salts and water.
    • Esterification: Carboxylic acids react with alcohols in the presence of an acid catalyst to form esters.
  1. Chemical Reactions: Decarboxylation
  • Decarboxylation is a reaction where a carboxylic acid loses a carbon dioxide molecule, resulting in the formation of an alkane.
  • Examples: Carboxylic Acid → Alkane + Carbon Dioxide
  • Decarboxylation is commonly observed in the preparation of aromatic compounds, such as the decarboxylation of benzoic acid to benzene.
  1. Application: Aromatic Aldehydes and Ketones
  • Aromatic aldehydes and ketones are commonly used in the fragrance and flavor industry.
  • Examples: Vanillin (found in vanilla), cinnamaldehyde (found in cinnamon), and benzaldehyde (found in almonds).
  • They impart characteristic aromas and flavors to various products.
  1. Application: Carboxylic Acids in Pharmaceuticals
  • Carboxylic acids are widely used in the pharmaceutical industry.
  • Examples: Aspirin (acetylsalicylic acid), ibuprofen (2-(4-isobutylphenyl)propanoic acid), and paracetamol (4-acetamidophenol).
  • Carboxylic acids can act as prodrugs, where they are converted to active forms in the body.
  1. Summary
  • Aldehydes, ketones, and carboxylic acids are important classes of organic compounds.
  • They have distinct structures and properties, including their nomenclature and physical characteristics.
  • Aldehydes and ketones can undergo various chemical reactions, including oxidation, reduction, and addition reactions.
  • Carboxylic acids have unique reactions, such as esterification and hydrolysis.
  • These compounds find numerous applications in industries such as fragrance, flavor, pharmaceutical, and more.
  1. Chemical Reactions: Aromatic Substitution
  • Aromatic aldehydes and ketones can undergo electrophilic aromatic substitution reactions.
    • Example: Benzaldehyde + Br2 → Bromobenzaldehyde
  1. Chemical Reactions: Acetal Formation
  • Aldehydes and ketones can react with alcohol in the presence of an acid catalyst to form acetals.
  • Example: Aldehyde or Ketone + Alcohol → Acetal + Water
  1. Chemical Reactions: Aldol Condensation (Crossed)
  • Aldol condensation can also occur between different aldehydes or ketones, resulting in the formation of a β-hydroxyaldehyde or β-hydroxyketone.
  • Example: Aldehyde 1 + Aldehyde 2 → β-Hydroxyaldehyde
  1. Chemical Reactions: Decarboxylation of β-Dicarboxylic Acids
  • β-Dicarboxylic acids can undergo decarboxylation to form α,β-unsaturated acids.
  • Example: β-Dicarboxylic Acid → α,β-Unsaturated Acid + Carbon Dioxide
  1. Chemical Reactions: Reactions of Carboxylic Acid Derivatives
  • Carboxylic acid derivatives include acid halides, acid anhydrides, esters, and amides.
  • These derivatives can undergo various reactions, including nucleophilic substitution and hydrolysis.
  • Example: Acid Chloride + Alcohol → Ester + HCl
  1. Application: Carboxylic Acids in Food Preservation
  • Carboxylic acids are commonly used as preservatives in food and beverages.
  • Examples: Benzoic acid, sorbic acid, and citric acid.
  • They inhibit the growth of bacteria, fungi, and other microorganisms.
  1. Application: Aldehydes and Ketones in Polymer Industry
  • Aldehydes and ketones are used in the polymer industry for the synthesis of resins and plastics.
  • Examples: Formaldehyde for the production of urea-formaldehyde and phenol-formaldehyde resins.
  1. Application: Carboxylic Acids in Dyeing and Printing
  • Carboxylic acids are used in the textile industry for dyeing and printing processes.
  • They help in binding dyes to the fabric and improving color fastness.
  1. Application: Ketones as Solvents
  • Ketones, such as acetone, are widely used as solvents in various fields.
  • They dissolve a wide range of compounds and are commonly used in laboratories and industries.
  1. Summary
  • Aldehydes, ketones, and carboxylic acids are versatile organic compounds with various applications in different industries.
  • They undergo diverse chemical reactions, including oxidation, reduction, addition, and substitution reactions.
  • These compounds play crucial roles in the synthesis of pharmaceuticals, fragrances, plastics, and other products.
  • Understanding their properties and reactions is essential for comprehending the field of organic chemistry.