M11- Carboxylic Acids

• Carboxylic acids


  Organic compounds having hydroxyl group attached to the acyl group
• Carboxylic acid derivatives


  Carboxylic acids where the hydroxyl group is substituted with other functional groups
• Carboxylic acids


  • Have high boiling points due to hydrogen bonds between the molecules
  • Form hydrogen bonds with water molecules which makes them soluble in water
  • Are colorless and have a particular odor
  • Can be in liquid form or wax
• Carboxylic acids have much higher boiling points than hydrocarbons, alcohols, ethers, aldehydes, or ketones of similar molecular weight
• Factors influencing boiling points and water solubility

  • Dipolar attractive forces between molecules
  • Hydrogen bonding
• Solubility of carboxylic acids in water

  • Similar to that of alcohols, aldehydes, and ketones
  • Acids with fewer than about five carbons dissolve in water
  • Solubility decreases with increasing number of carbon atoms due to increased hydrophobic interaction of hydrocarbon part
  • Also soluble in less polar organic solvents like benzene, ether, alcohol, chloroform, etc.
• Carboxylic acids


  • Carboxylic acids with less than ten number of carbon atoms are colorless liquids at room temperature
  • Carboxylic acids with more than 10 carbon atoms are wax like solids
  • The higher acids are wax like solids due to their low volatility
• Carboxylic acids


  • Many are colorless liquids with disagreeable odors
  • Carboxylic acids with 5 to 10 carbon atoms all have "goaty" odors
  • The acids with more than 10 carbon atoms are waxlike solids, and their odor diminishes with increasing molar mass and resultant decreasing volatility
  • Produced by the action of skin bacteria on human sebum (skin oils), which accounts for the odor of poorly ventilated locker rooms
• Acidity of carboxylic acids

  They are generally more acidic than other organic compounds containing hydroxyl groups but are generally weaker than the familiar mineral acids (e.g., hydrochloric acid, HCl, sulfuric acid, H2SO4, etc.)
• Carboxylic acid derivatives


  • Acyl phosphate
  • Thioester
  • Ester
  • Carboxylic acid
  • Amide
  • Carboxylate
• Acyl phosphate


  • An acyl group with a phosphate attached to the oxygen
  • Enzymes activate a carboxylate group by converting it to an acyl phosphate, at the expense of an ATP
  • Can also be formed by removing hydrogen from the oxygen of a carboxylic acid and replace it with phosphate
• Converting carboxylic acid to acyl chloride

  1. Using phosphorus(V) chloride, phosphorus(III) chloride, or sulfur dichloride oxide (thionyl chloride)

  2. Acyl chlorides are very reactive, and can be used to make a wide range of other things
• Forming acid anhydrides


  1. By heating two carboxylic acids at a high temperature of nearly 800℃, removing one water molecule

  2. Can also be synthesized by the reaction of a carboxylic acid with P2O5
• Carboxylic acid derivatives


  • Undergo various types of reactions including acyl group substitution, reduction, reactions with organometallic reagents
• Nucleophilic attack on carboxylic acid derivatives

  1. Nucleophiles attack the carboxylic acid derivatives from one side of the carbonyl carbon, converting it to tetrahedral geometry

  2. The X group serves as the leaving group and when it leaves, the carbon reforms double bond with oxygen

  3. At the end of reaction, nucleophile becomes the new X group
• Reactivity of carboxylic acid derivatives

  • Acyl phosphate (most reactive)
  • Thioester
  • Ester
  • Carboxylic acid
  • Amide
  • Carboxylate (least reactive)
• Reduction of carboxylic acid derivatives

  1. To either aldehydes or alcohols

  2. Reduction reactions include catalytic dehydrogenation, complex metal hydride reactions, diborane reduction

  3. Acyl halides are reduced to aldehyde in the presence of palladium as catalyst under mild conditions
• Reaction of carboxylic acid derivatives with organometallic compounds

  Esters react with Grignard reagents to form tertiary alcohols