SPM Chemistry Form 5 Notes – Terminology and Concepts: Carbon Compounds (Part 7)

by BerryBerryTeacher

in Berry Reference (Notes)

Berry Berry Easy is back with Part 7 of the super long Carbon Compound series for SPM Form 5 Chemistry. Continuing from Part 5 and 6, where non-hydrocarbon alcohol and carboxylic acids were featured, respectively, Part 7 is about non-hydrocarbon esters. Based on feedback from previous students, most find that esters are relatively difficult to be understood (harder than carboxylic acids but still than alcohol). So please revise Part 5 and 6 before hopping into Part 7.

SPM Form 5 – Terminology and Concepts: Carbon Compounds (Part 7)

Non-Hydrocarbon – Esters

1. General formula: CnH2n+1COOCmH2m+1
Where n = 0, 1, 2, 3 … and m = 1, 2, 3 … (n and m = number of carbon)
R
COOR‘ where R and R‘ represented the same or different alkyl groups.

2. Esters are non-hydrocarbons which contain carbon, hydrogen and oxygen atoms.

3. The functional group in ester is carboxylate group, – COO -.
CnH2n+1COOH + CmH2m+1OH –> CnH2n+1COOCmH2m+1 + H2O

  • First part: taken from the alcohol (alkyl group)
  • Second part: taken from the carboxylic acid (-oic to -oate)
Name of ester Molecular formula of ester Prepared from
Ethyl methanoate HCOOC2H5 Ethanol + Methanoic acid
Methyl ethanoate CH3COOCH3 Methanol + Ethanoic acid
Propyl ethanoate CH3COOC3H7 Propanol + Ethanoic acid
Ethyl propanoate C2H5COOC2H5 Ethanol + Propanoic acid

4. Physical properties of ester

Name Odour
3-metylbutyl acetate Banana
Ethyl butanoate Pineapple
Octyl ethanoate Orange
Isoamyl isovalerate Apple
  • Simple esters are colourless liquid and are found in fruits and flowers.
  • Esters have sweet pleasant smell.
  • Esters are covalent compounds.
  • Esters are insoluble in water but soluble in organic solvent.
  • Esters are less dense than water.
  • Esters are neutral and cannot conduct electricity.
  • The higher and more complex esters have higher boiling points and less volatile.

Natural sources:

  • Vegetable oils (palm oil) and liquids esters can be found in plants derived from glycerol and fatty acids.
  • Fats are solid esters (milk fat) derived from glycerol and fatty acids.
  • Waxes (beewax) are solid ester derived from long-chain fatty acids and long-chain alcohols.

5. Uses of Esters

  • Preparation of cosmetics and perfumes (esters are volatile and have sweet smell).
  • Synthetic esters used as food additives (artificial flavour).
  • Natural esters serves as storage reserve of energy in living things.
  • In plant, wax (esters) helps to prevent dehydration and attack of microorganisms.
  • Esters used as solvents for glue and varnishes.
  • Esters used to make plastics softer.
  • Esters used to produce polyester (threads and synthetics fabrics)
  • Esters used to produce soap and detergents.

So for Form 5 SPM Chemistry students, be sure to come back for the final two parts in the carbon compound series to be published berry berry soon.

Previous post:

Next post: