esters

HideShow resource information
  • Created by: danni :)
  • Created on: 04-12-12 10:07
View mindmap
  • THE WONDERFUL WORLD OF ESTERS
    • SYNTHESIS OF ESTERS
      • carboxylic acid + alcohol --> ester +water
        • RCOOH + ROH --> RCOOR +H2O
      • slow reaction and subject to equilibrium : easier to use a more reactive acyl chloride or acid anhydride
        • e.g.,  ethanoyl chloride + ethanol --> ethyl ethanoate +HCl
        • ethanoic anhydride + ethanol --> ethyl ethanoate + ethanoic acid
    • naming esters
      • names starts with an alkyl word derived from the alcohol (e.g., methanol= methyl)
      • second part is the name of the acid used replacing -oic with -oate.
    • Properties of esters
      • volatile
      • don't form hydrogen bonds so have relatively low melting and boiling points
      • not very soluble in water or any other polar solvents
      • fruity/ flowery smell
    • reactions of esters
      • hydrolysis: reverse reaction of esterification in which the ester splits to form the original alcohol and acid
      • acid hydrolysis:  esters can be split by boiling with water and much more effectively by using a dilute acid. the acid is a catalyst and the reaction is reversible unlike base hydrolysis
      • base hydrolyis: boil with potassium hydroxide. more efficient  because when the acid is released it is neautralised by alkali to from potassium salt. sometimes called saponification
    • uses of esters
      • biodiesels
        • made from vegetable oils.  tend to clog fuel injection nozzles. needs to be more volatile so is obtained by transesterification. forms methyl esters
          • margarine
            • Can be made by partial hydrogenation: controlled amount of hydrogen  is added to the oil in the presence of a catalyst (usually nickel)
              • advantage: no interference with the order of the fatty acids on the triol
              • disadvantage: some trans isomers are formed which are believed to increase blood cholesterol.
          • advantage: no trans fatty acids produced
          • disadvantage: some stearic acid moves to middle carbon of triol which is believed to be harmful to health.
        • glycerol acids of three fatty acids + three molecules of methanol --> glycerol + methyl esters of three fatty acids
      • margarine
        • Can be made by partial hydrogenation: controlled amount of hydrogen  is added to the oil in the presence of a catalyst (usually nickel)
          • advantage: no interference with the order of the fatty acids on the triol
          • disadvantage: some trans isomers are formed which are believed to increase blood cholesterol.
    • polyesters
      • a condensation polymer is formed when monomers join together with the elimination of a simple molecule such as water or chlorine
      • a homopolymer is made from a single type of monomer. it must have a group at one end that can react with the group at the other end e.g., hydroxyacids
      • polyesters are not biodegradeable because enzymes haven't evolved that can hydrolyse the ester linkages in artificial fibres

Comments

Patrick I

this is super thanks for sharing!

danni :)

thanks and you're welcome :)

danni :)

thanks and you're welcome :)

apselv

  • this is really good! :) 

Similar Chemistry resources:

See all Chemistry resources »See all Functional Groups resources »