Carboxylic acids and esters

• Carboxylic acid functional group

  C double bond O, single bond O H
• Solubility of carboxylic acids in water

  • Carboxylic acids are soluble due to hydrogen bonding between the carboxylic acid and water
  • Longer carbon chain decreases solubility as it prevents hydrogen bonding
• First 4 carboxylic acids (methanoic to butanoic) are fully miscible in water
• Carboxylic acids with 5 or more carbons have decreasing solubility in water
• Longer carbon chain in carboxylic acid

  Less able to form hydrogen bonds with water, decreasing solubility
• Acids


  Proton donors
• Carboxylic acids


  Weak acids that partially dissociate
• Partial dissociation of carboxylic acids

  1. Carboxylic acid

  2. Carboxylate ion

  3. Proton (H+)
• Carboxylate ion


  Negatively charged ion formed from the partial dissociation of a carboxylic acid
• Carboxylic acids will react with metals, bases, and carbonates to form salts
• Reaction of carboxylic acid with metal

  1. Carboxylic acid

  2. Metal

  3. Salt

  4. Hydrogen
• Reaction of carboxylic acid with base

  1. Carboxylic acid

  2. Base

  3. Salt

  4. Water
• Reaction of carboxylic acid with carbonate

  1. Carboxylic acid

  2. Carbonate

  3. Salt

  4. Water

  5. Carbon dioxide
• Ester


  Functional group with an R group, a C=O and C-O bond, and another R group
• Ester functional group

  • R group can be the same or different
  • R group cannot be H (would be a carboxylic acid)
• Making esters from carboxylic acids and alcohols

  1. Use carboxylic acid (e.g. ethanoic acid)

  2. Use alcohol (e.g. methanol)

  3. Reaction requires heat and concentrated sulfuric acid catalyst
• Making esters from acid anhydrides and alcohols

  1. Break bond in acid anhydride

  2. Break bond in alcohol

  3. Produces ester and carboxylic acid

  4. Does not require sulfuric acid catalyst, just needs heat
• Acid anhydride


  Two carboxylic acid molecules joined together with loss of water molecule
• Acid anhydride examples

  • Ethanoic anhydride
  • Methanoic anhydride
• Esters made from acid anhydrides and alcohols produce an ester and a carboxylic acid
• Esterification


  Reaction of alcohols to produce esters
• Esters made from acid anhydrides do not require a sulfuric acid catalyst, just heat
• Esterification reaction


  1. Carboxylic acid

  2. Alcohol

  3. Ester

  4. Water
• Conditions for esterification


  • Heat
  • Concentrated sulfuric acid catalyst
• Carboxylic acid

  General formula: RCOOH
• Alcohol

  General formula: R-OH
• Ester


  Formed from the R group of the carboxylic acid and the R group of the alcohol
• Specific example of esterification

  • Ethanoic acid (carboxylic acid) + Methanol (alcohol) → Methyl ethanoate (ester) + Water
• Naming esters


  Name the ester backwards - first part from the alcohol, second part from the carboxylic acid
• Example ester name


  • Methyl ethanoate
• Example esterification reaction

  • Propanoic acid + Ethanol → Ethyl propionate + Water
• For esterification with secondary alcohols, the ester bond forms in the middle of the molecule, not at the end
• Complex esterification example

  • Carboxylic acid + Alcohol → Ester + Water
• Hydrolysis


  The chemical breakdown of a substance by reaction with water
• Ester hydrolysis


  1. Break the ester bond by reacting with water

  2. Can be acid hydrolysis or alkaline hydrolysis
• Acid hydrolysis of esters


  • Reflux ester with dilute aqueous acid (e.g. hydrochloric acid or sulfuric acid)
  • Breaks the ester bond
  • Produces a carboxylic acid and an alcohol
• Alkaline hydrolysis of esters


  1. Reflux ester with aqueous alkali (e.g. sodium hydroxide or potassium hydroxide)

  2. Breaks ester bond

  3. Produces carboxylate salt and alcohol
• Esters use

  Used in soap manufacture, flavourings and perfumes
• Esters have pleasant sweet smells and flavors
• Acyl group


  General formula: R-C=O