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)
RCOOR‘ 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
- 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.
- 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.