Esters

If the acid and alcohol have functional groups on both ends of the molecule, they can make many ester groups, resulting in a polyester (condensation polymer)

Reactions of esters

• Acid hydrolysis

  • The reverse of the esterification

  • Makes carboxylic acid and alcohol

• Alkaline hydrolysis

  • React with hot aqueous NaOH

  • Makes carboxylate salt and alcohol

Uses of esters

• Small chained esters are used in perfumes and food flavourings

  • Smell nice and are volatile (vaporise easily)

• Glycerol, propane 1, 2, 3 triol

  • Can react glycerol with fatty acids (carboxylic acids) to form triglycerides (esters)

  • Animal and vegetable oils and fats are triglycerides

  • Hydrogen bonds as well as Van der Waals forces

  • Relatively high melting/boiling points

  • Can form hydrogen bonds to water so very soluble in water

Triglycerides (esters)

• Alkaline hydrolysis

  • Boil was NaOH

  • Forms glycerol + carboxylate salts (soaps)

  • Carboxylate salts have a polar (mixes with water) and non polar end (mixes with oils/grease). They allow grease and water to mix so are used for cleaning products

• Methanol + alkali catalyst

  • Glycerol + biodiesel

  • Mixture of methyl esters

  • Can be used as a fuel