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identifcation of and organic unknown

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Identification of an organic unknown Plan Introduction In this investigation I will get a number of unknown organic compounds to which I have to identify using a number of simple chemical tests. The flow-chart below shows these simple tests that I will use to identify the functional groups of the unknowns. General safety procedures Always wear gloves and goggles when handling any unknown because some materials could be corrosive or an irritant. Be careful when disposing organic materials insure there is an organic waste beaker or bucket available. 1. Test unknown with acidified potassium manganate. THEROY: Manganate (VII) ions are a strong oxidising agent, and in the first instance oxidise ethene to ethane-1,2-diol causing the colour change from purple to colourless. The equation is as follows; C2H4 + H2O + {O} C2H6O2 EQUITMENT: pipettes, Test tube, Beaker of warm water. SAFETY: follow general safety procedures. PROCEDURE: Add 1cm3 of potassium manganate to a test tube also add 1cm3 of sulphuric acid to the test tube and also add a few drops of the unknown, final place the test tube in a beaker of warm water. ...read more.


SAFETY: always follow general safety procedures, 2,4-DNPH is explosive and toxic and ethanol is extremely flammable, so take extra care when appropriate and ensure Bunsen burners are switched off in the presence of any flammable chemical. PROCEDURE: To 1cm� of 2,4-dinitrophenylhydrazine solution and 1cm� of ethanol, add several drops of the carbonyl, ester or alcohol unknown via pipette, Heat with a water bath if necessary. OBSERVATIONS: A colour change to orange/yellow indicates the presence of a carbonyl group, which will be an aldehyde or a ketone. No colour change indicates that it is an alcohol, or ester. 5. Test unknown with tollens reagent THEROY: Aldehydes are easily oxidised to acids. Ketones cannot be oxidised, as there is no place for the oxygen from the oxidising agent. Tollens reagent consists of silver nitrate and ammonia to form the complex ion {Ag (NH3)2} this is reduced to silver in the reaction with the aldehyde forming a silver mirror. EQUIPMENT: Test tube Pipette Silver nitrate solution Sodium hydroxide solution Ammonia solution Water Bath SAFETY: Follow general safety procedures and silver nitrate solution, sodium hydroxide solution and ammonia solution are all corrosive so handle with care. ...read more.


PROCEDURE: add equal amounts of HCL and ZnCl2 to a test tube then add several drops of the alcohol and ester unknown and shake gently. OBSERVATIONS: no change indicates an ester; cloudy very quickly indicates a tertiary alcohol. 8. Confirmation of carboxylic acid with addition of base THEROY: Because of their enhanced acidity, carboxylic acids react with bases to form ionic salts, as shown in the following equation. RCO2H + NaHCO3 RCO2 (-) Na (+) + CO2 + H2O EQUITMENT: Pipette test tube NaHCO3 SAFTY: Take care when handling acids and bases as irritation to the skin can be caused, always follow general safety procedures. PROCEDURE: Add equal amounts of unknown with the NaHCO3 into a test tube using a pipette and shake gently. OBSERVATIONS: after a few seconds and salt precipitate should start to form, confirming the unknown to be a carboxylic acid. 9. Confirmation of ester by hydrolysis THEROY: Hydrolysis is simply a reaction with water, the hydrolysis of an ester produces an alcohol and a carboxylic acid the reaction is in equilibrium as shown below EQUITMENT: Test tube Pipette HCl Water SAFETY: follow general safety procedure, handle chemicals with care. ...read more.

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