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I have been supplied with an unknown organic compound containing one of the following functional groups: Alkene Primary alcohol Tertiary

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Introduction

Assessed practical (skills P and A) Introduction I have been supplied with an unknown organic compound containing one of the following functional groups: * Alkene * Primary alcohol * Tertiary alcohol * Aldehyde * Ketone * Carboxylic acid * Ester * Phenol The organic compounds above all have different functional groups, and will react differently. Therefore in order to identify the functional group that the unknown compound contains I will carry out a series of experiments. I had to choose carefully which tests to use because each test should be dependant on the result of the previous test. Method 1) Test for the presence of an alkene: Bromine test Add 5 drops of bromine solution (a brown/orange colour) to 2cm of the unknown compound. Indication of a positive test The orange/brown solution decolourises. 2) Test for the presence of a primary alcohol: Heat the unknown organic compound gently (reflux) with potassium dichromate (VI), which is an oxidising agent, and concentrated H SO in distilling apparatus. Indication of a positive test The orange solution turns green, as the orange dichromate (VI) ...read more.

Middle

Drop by drop add ammonia solution until the precipitate of silver oxide dissolves. Add one or two drops of the unknown compound, shake the tube gently and place in a beaker of warm water. A positive test is indicated by: A silver mirror is produced on the sides of the test tube from the colourless solution. 6) Test for an alcohol (-OH) group Add three drops of the compound to be tested to 10drops of an acidified cerric ammonium nitrate solution (a yellow solution) The alcohol complexes with the cerric nitrate ion A positive test is indicated by: The immediate formation of red or red-brown colour indicates a positive test. If the unknown compound is not soluble in water, two layers will be present. A red colour in either layer will indicate a positive test. 7) Test for the presence of a carboxylic acid: Sodium bicarbonate test An acid/base reaction occurs. Sodium bicarbonate reacts with the carboxylic acid to give off carbon dioxide gas. Add a few drops of the unknown compound to 1cm of methanol and slowly add to 1cm of a saturated solution of sodium bicarbonate. ...read more.

Conclusion

Add 5 drops of FeCl solution (a yellow solution) to a test tube containing 2 drops of the unknown compound. A positive test is indicated by: The solution changes colour to a purple. . Risk Assessment * Phenolphthalein can cause skin contamination, always wear rubber gloves when handling. * Sodium Hydroxide is corrosive and an irritant. Handle carefully by wearing gloves and goggles * Potassium dichromate (VI) is toxic if inhaled, handle carefully and do not leave bottles uncapped. * Iron (III) chloride is irritating to eyes and skin so wear gloves and protective goggles. * 2,4 DNPH is toxic by skin contact. * Organic substances are flammable so all heating should be carried out in a water bath. * Clean up all chemical spills immediately, and dispose of all waste as directed. Apparatus * 10cm measuring cylinder * Teat pipette * Test tube rack * Water bath * Small beaker * Distilled water * Large beakers Reagents * 2,4-dinitrophenylhydrazine (DNPH) (aq) * 20 drops of 2M ammonia solution * 20 drops of 2M sodium hydroxide solution * Limewater * 5 drops Iron Chloride (5% FeCl ) * 5 drops Phenolphthalein indicator * 5 drops Bromine solution * Potassium dichromate (VI) (aq) * Concentrated sulphuric acid (aq) * 1cm 0. ...read more.

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