Thursday 26 February 2015

2.7.1 - Laboratory Activity : Preparation of Ester in Laboratory


Laboratory Activity 2.7.1:
Preparation of Ester in Laboratory
Aim: To prepare ester in laboratory

Material:
» Ethanol, C2H5OH
» Ethanoic acid, CH3COOH
» Concentrated sulphuric acid
» Porcelain pieces
» Water

Apparatus:
» Liebig condenser
» Beaker
» Tripod stand
» Wire gauze
» Round-bottomed flask
» Retort with stand
» Bunsen burner
Procedure:

(A) Preparation of ethyl ethanoate
1.
2. 20cm3 of ethanol and 10cm3 of ethanoic acid is added into a round-bottomed flask.
3. 2cm3 of concentrated sulphuric acid is added to the mixture.
4. A few small pieces of porcelain are added to the flask.
5. The mixture is heated under reflux for about 30 minutes.

(B) Distillation of ethyl ethanoate
1.
2. Distillation process at a temperature range of 77°C – 80°C is used to obtain ethyl ethanoate from the mixture of product.

(C) Purifying the distillate of ethyl ethanoate
1.
Removal of ethanoic and sulphuric acid
The distillate is poured into a separating column.
Sodium carbonate is added slow into the distillate until no more effervescence occurs.
The bottom layer (water) is removed and the process is repeated until all the acids are removed.
2.
Separation of ethyl ethanoate and ethanol
Distilled water is added. The mixture is then shaken strongly and allowed to rest.
Two layers of liquid will form after few minutes.
The bottom layer is then drained out, and the upper layer is poured into a conical flask.
3.
Removal of water
Some anhydrous calcium chloride is used to dry ethyl ethanoate and the mixture is then filtered.
A colourless liquid with a fragrant smell is produced.
Obervation:

The following animation shows the arrangement of apparatus and the observation of the experiment.
Analysis: 

(A) Preparation of ethyl ethanoate
Ethanoic acid and ethanol reacts to from ethyl ethanoate.
C2H5OHethanol+CH3COOHethanoic acid concentrated sulphuric acid CH3COOC2H5 ethyl ethanoate+H2O
The mixture needs to be heated under reflux to avoid loss of volatile substances.
Water bath is used to ensure evenly heating of the solution.

(B) Distillation of ethyl ethanoate
The distillate contains impurities such as ethanol and ethanoic acid.

(C) Purifying the distillate of ethyl ethanoate
The sodium carbonate solution is used to neutralise the ethanoic acid and sulphuric acid so that the acid impurities can be removed.
When water is added, two layers of liquid are formed.
Conclusion:

Pure ester (ethyl ethanoate) can be prepared with the reaction between a carboxylic acid and an alcohol.


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