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:

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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. $\begin{array}{c}{C}_2{H}_5\mathit{OH}\\ \text{ethanol}\end{array}+\begin{array}{c}{\mathit{CH}}_3\mathit{COOH}\\ \text{ethanoic acid}\end{array}\begin{array}{c}\mathrm{\rightleftharpoons }\\ \text{concentrated sulphuric acid}\end{array}\begin{array}{c}{\mathit{CH}}_3{\mathit{COOC}}_2{H}_5\\ \text{ethyl ethanoate}\end{array}+H_{2}O$ ○ 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:

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

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