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In I/GCSE Chemistry, we will learn about Esters – COO group 2E.
Properties
- Fruity smell b/c organic
- Low molecular mass + B.P = (molecules evaporate quickly ) good for solvents
- Highly flammable
- Some can hydrolyse back to original reactants
- Acetate is a colourless liquid at room temp.
Uses
- Flood flavourings
- Perfumes
- Solvents
- Plasticsers
In I/GCSE Chemistry, Extracting natural esters is too expensive. Instead you can make synthetic “nature identical” esters.
Alcohol + Carboxylic acid [+sulphuric ester catalyst] --> Ester
Making an ester
Refluxing
- Ethanol + Ethanoic acid + conc. Sulfuric acid is in the flask
- Heating speeds up the reaction, although gently so that the ethanol doesn’t evaporate/ catch on fire
- The flask is fitted with a condenser
- The condenser catches the ethanol vapour and recycles it back into the flask
- This enables the chemicals to react
Distillation (separating ester from waste chemicals)
- Reacted mixture is heated below a fractionating column (FC)
- As mixture boils, vapour goes up FC
- When temp. at top of the FC reaches boiling point of ethyl ethanoate, it become a liquid
- The liquid flows through condenser and is collected in a container
- The liquid is impure ethyl ethanoate
Purification
- In I/GCSE Chemistry, The distillate ( liquid collected) is poured into a tap funnel
First part
- The mixture is shaken with the aqueous reagent, sodium carbonate (Na2SO3),to remove acidic impurities
- The mixture separates into two layers b/c the ethyl ethanoate doesn’t mix with the water in the sodium carbonate solution
- The top layer is ethyl ethanoate. The lower layer is sodium carbonate solution.
- The lower layer can be tapped off
Second part
- The remaining upper layer is shaken with conc. calcium chloride (CaCl2).
- The CaCl2 removes any remaining ethanol
- The lower layer is tapped off again
- Only ethyl ethanoate and some water in the solution remains
Drying
- In I/GCSE Chemistry, Water still remains in the solution
- Anhydrous granules of calcium chloride (a drying agent) can absorb the water
Filtration
- The granules/ lumps of calcium chloride can be filtered
- Only pure ethyl ethanoate remains
You got it now!
