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3. Addition of Water (Hydration) |
- Alkenes react with water (in the form of steam) at high temperature and pressure, in the presence of phosphoric acid, H3 PO4 as a catalyst to produce alcohol.
- Catalyst: phosphoric acid.
- Temperature: 300°C.
- Pressure: 60 atm.
- This reaction is also called the hydration reaction.
- Product: Alcohol.
\(\,\\C_2H_4(g) + H_2O(ce) \xrightarrow []{H_3PO_4}C_2H_5OH(ce)\)
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4. Acidified potassium manganate(VII) solution, KMnO4 |
- Acidified potassium manganate(VII) solution is a very good oxidising agent.
- This reaction is also called the oxidation reaction.
- Product: Diol (Alcohol with two hydroxyl groups).
\(C_2H_4(g) + H_2O(l) \xrightarrow []{[O]} CH_2OHCH_2OH(l)\)
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- The pair of electrons making up one of the double bonds is shared with the carbon atom of another alkene molecule in the polymerisation reaction.
- Example: polymerisation of ethene:
- Polymer: polyethene.
- Monomer: ethene.
- Pressure: 2000 atm.
- Temperature: 100°C to 300°C.
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Penyediaan Etanol |
Production of Ethanol in the Indutry |
- Addition reaction with water (steam)
- Catalyst: phosphoric acid.
- Temperature: 300°C.
- Pressure: 60 atm.
- \(C_2H_4(g) + H_2O(l) \xrightarrow[]{H_3PO_4} C_2H_5OH(l)\)
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Production of Ethanol in the Laboratory |
- The fermentation process of carbohydrate or sugary substances like rice, barley or fruits
- These substances contain glucose.
- Zymase in yeast acts as a catalyst to convert glucose to ethanol.
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- \(C_6H_{12}O_6(aq) \xrightarrow[]{yis} 2C_2H_5OH(l) + 2CO_2(g)\)
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Chemical Properties of Ethanol |
- Combustion of ethanol in excess oxygen produces carbon dioxide and water.
- \(C_2H_5OH(l) + 3O_2 (g) \rightarrow 2CO_2(g) + 3H_2O(l)\)
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- Ethanol is oxidised by acidified potassium dichromate(VI) solution.
- Product: ethanoic acid
- Dichromate ion (orange) changes to chromium ion (green).
- \(C_2H_5OH(l) \xrightarrow[]{[O]} CH_3COOH(l)\)
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- A water molecule is eliminated from the reaction.
- Catalyst: sulphuric acid.
- Temperature: 180°C.
- Product: ethene.
- \(C_2H_5OH(l) \xrightarrow[]{H_2SO_4, 180^\circ C} C_2H_4(g) + H_2O(l)\)
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Preparation of Ethanoic Acid in the Laboratory |
- Oxidation of ethanol
- Ethanol is oxidised by acidified potassium dichromate(VI) solution.
- Dichromate ion (orange) changes to chromium ion (green).
- \(C_2H_5OH(l) \xrightarrow[]{[O]} CH_3COOH (l)\)
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Chemical Reactions of Ethanoic Acid as An Acid |
Reaction with Base or Alkali |
- Product: salt and water
- Also known as neutralisation reaction.
- Example of reaction with sodium hydroxide:
- \(CH_3COOH (aq) + NaOH(aq) \rightarrow CH_3COONa (aq) + H_2O(l)\)
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Reaction with Reactive Metal |
- Product: salt and hydrogen gas
- Example of reaction with magnesium:
- \(2CH_3COOH (aq) + Mg(s) \rightarrow (CH_3COO)_2Mg (aq) + H_2(g)\)
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Reaction with Metal Carbonate |
- Product: salt, carbon dioxide gas and water
- Example of reaction with calcium carbonate:
- \(2CH_3COOH (aq) + CaCO_3(s) \rightarrow (CH_3COO)_2Ca(aq) + H_2O(l) + CO_2(g)\)
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The Chemical Reaction of Ethanoic Acid with An Alcohol |
- Product: ester.
- Also known as an esterification reaction.
- Catalyst: hydrogen ion.
- \(CH_3COOH (aq) + C_2H_5OH(l) \xrightarrow []{H^+}CH_3COOC_2H_5(aq) + H_2O(l)\)
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Ester |
- Functional group: carboxylate group, \(-COOC-\)
- General formula: \(C_nH_{2n+1}COOC_mH_{2m+1}\), where n = 0,1,2,… and m = 1,2,3,…
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Naming Ester |
- Ester is produced by combining alcohol with carboxylic acid.
- There are two parts to naming an ester.
- The first part is based on the name of the alcohol.
- The second part is based on the name of the carboxylic acid.
- Example: Ethyl butanoate.
![The diagram shows the structural formula of ethyl butanoate.](https://question.pandai.org/uploads/image/228677/KSSM-CH-11-02-ester-01.png)
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Steps in Naming An Ester |
- Determine the alkyl group of the alcohol chain based on the structural formula or the molecular formula.
- Determine the name of the carboxylic acid part.
- Change the term ‘oic’ in carboxylic acid to ‘oate’.
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Preparation of Ethyl Ethanoate in Laboratory |
- Mixing ethanoic acid with ethanol by reflux reaction.
- Reflux is needed because ethanol is a volatile solution.
- \(CH_3COOH(aq)+ C_2H_5OH(aq) \xrightarrow[]{ H_2SO_4} CH_3COOC_2H_5(aq)+H_2O(l)\)
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Physical Properties of Ethyl Ethanoate |
- A colourless solution at room temperature.
- Nice fruity smell.
- Soluble in water.
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Esterification Ester |
- Product: ester.
- Also known as an esterification reaction.
- Catalyst: hydrogen ion.
- Example of esterification reaction of ethanoic acid with ethanol:
- \(CH_3COOH(aq)+ C_2H_5OH(aq) \xrightarrow[]{ H_2SO_4} CH_3COOC_2H_5(aq)+H_2O(l)\)
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![This image is a diagram illustrating the various uses of esters. At the center, there is a box labeled ‘USES OF ESTER.’ Surrounding this central box are six other boxes connected by lines. Each of these boxes contains a different use of esters: 1. Explosives 2. Insect repellent 3. Detergent 4. Solvents 5. Perfumes 6. Food flavourings The background is white, and the boxes are in shades of blue. The diagram is branded with the ‘Pandai’ logo at the bottom right corner.](https://question.pandai.org/uploads/image/134073/Uses_of_esther_-_Copy.jpg) |
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Natural Sources of Ester |
Flower or Fruit |
Ester |
Jasmie
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Benzyl ethanoate |
Pear
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Propyl ethanoate |
Apricot
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Pentyl propanoate |
Kiwi
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Methyl benzoate |
Pineapple
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Ethyl butanoate |
Banana
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3-methylbutyl ethanoate |
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