Friday, September 17, 2010
Monday, September 6, 2010
Monday, August 30, 2010
Testing for Aldehydes and Ketones
Only Aldehydes will react with any of the tests outlined below because they can be oxidised furter to the carboxylic acid. Ketones will not react so there will not be any colour change.
Benedicts solution
Fehlings solution
Tollens Test
Benedicts solution
Fehlings solution
Tollens Test
Reactions of alkenes and alcohols
http://prezi.com/td-h0senlhw9/y13-reactions-of-alkenes-and-alcohols/
Thursday, August 26, 2010
Organic chemistry -Ester preparation -The steps involved.
Method
1. The carboxylic acid and alcohol are heated by reflux with a little conc H2SO4 as a catalyst for 30 minutes.
The mixture is refluxed to allow the reaction mixture to be heated with out the loss of reactant which is very volatile. The reactant evaporates and rises up into the condenser which is cooled with water flowing in a separate tube around the outside. It the condenses back down into the reaction flask.
2. The mixture is then allowed to cool and then the excess acid is neutralised by the addition of sodium carbonate solution.
Sodium carbonate solution is added to react with remove the sulfuric acid from the reaction mixture, therefore stopping the reaction.
3. The resulting mixture is then placed into a separating funnel and the bottom aqueous layer is then poured off.
A separating funnel allows easy removal of the water from the organic layer as the organic layer sits on the top.
4. The remaining organic layer is then washed with more sodium carbonate solution and again the aqueous layer is poured off.
This is done to remove any remianing acid. which gets neutralised by the sodium carbonate solution.
5. Anhydrous Magnesium sulfate is then added to the organic layer to remove any remaining water.
Anhydrous magnesium sulfate binds to any water in the organic layer, therefore removing the water and making the organic layer 'dry'.
6. The solid magnesium sulfate is then filtered off and the organic layer is distilled to collect the pure ester.
1. The carboxylic acid and alcohol are heated by reflux with a little conc H2SO4 as a catalyst for 30 minutes.
The mixture is refluxed to allow the reaction mixture to be heated with out the loss of reactant which is very volatile. The reactant evaporates and rises up into the condenser which is cooled with water flowing in a separate tube around the outside. It the condenses back down into the reaction flask.
2. The mixture is then allowed to cool and then the excess acid is neutralised by the addition of sodium carbonate solution.
Sodium carbonate solution is added to react with remove the sulfuric acid from the reaction mixture, therefore stopping the reaction.
3. The resulting mixture is then placed into a separating funnel and the bottom aqueous layer is then poured off.
A separating funnel allows easy removal of the water from the organic layer as the organic layer sits on the top.
4. The remaining organic layer is then washed with more sodium carbonate solution and again the aqueous layer is poured off.
This is done to remove any remianing acid. which gets neutralised by the sodium carbonate solution.
5. Anhydrous Magnesium sulfate is then added to the organic layer to remove any remaining water.
Anhydrous magnesium sulfate binds to any water in the organic layer, therefore removing the water and making the organic layer 'dry'.
6. The solid magnesium sulfate is then filtered off and the organic layer is distilled to collect the pure ester.
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