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
| 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.
