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Identification of an organic unknown

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Introduction

Identification of an organic unknown Introduction In this chemistry coursework, I am supplied with an unknown organic compound containing one of the following functional group: * Alkene * Primary alcohol * Tertiary alcohol * Aldehyde * Ketone * Carboxylic Acid * Ester * Phenol I am going to outline a sequence of simple chemical test that I could use to identify each group. Each test must be dependant on the result of previous test. I am going to write up a plan include a flow chat, and a procedure which provides fully details of each test with the expected observations and any necessary safety precaution. Also I will need to consider the equipment and apparatus and chemicals use. Primary and Tertiary alcohol Oxidation can be used to decide whether it a primary or tertiary alcohol. Oxidation with acidified potassium dichromate(VI) solution results in a colour change from orange to green due to the formation of Cr3+ ions, as long as there is not an excess of dichromate present. A colour change will therefore only occur with primary and secondary alcohol. The Lucas test is another way of distinguishing between primary and tertiary alcohols. It depends on substitution of chlorine for the hydroxyl group. The alcohol is shaken hard in a stoppered flask with concentrated hydrochloric acid and anhydrous zinc chloride. The flask is then allowed to stand. ...read more.

Middle

very flammable; therefore I must keep the stopper on the bottle as much as possible, keep the bottle away from flames and wear safety spectacles Tollens' reagent becomes explosive on evaporation. Therefore wash away residues immediately after use. Procedure 1. Put about 1cm3 of 0.05M AgNO3 into a very clean test tube and add three or four drops of sodium hydroxide solution. 2. Drop by drop, add ammonia solution until the precipitate of silver oxide nearly dissolves (do not try to get rid of all the little black specks of silver oxide). 3. Add one or two drops of unknown, shake the tube gently and place in a beaker of warm water. 4. Note observations and immediately rinse out the test tube. Positive results If a shinny silver mirror form, aldehydes presents. Negative results Ketones have no reaction with Tollens test. Fehling's test Fehling's test are similare to Tollens' test, except that copper(II) is used instead of silver(I) as the oxidizing agent. Fehling's regent must be freshly prepared before each used. Fehling's solution A is awueous copper(II) sulphate; Fehling's solution B contains alkali and tartrate ions. Equal volumes of Fehling's A and B should be mixed to give a deep blue solution of copper(II) tartrate complex. Equations Apparatus Safety spectacles Protective gloves Fehling's solution A and B Test tubes Hazards The unknown compound could be is very flammable; therefore I must keep the stopper on the bottle as much as possible, keep the bottle away from flames and wear safety spectacles Fehling's solution is corrosive, Safety spectacles and gloves must wear Procedure 1. ...read more.

Conclusion

Test tubes Hazard Warning Both phenol and bromine water attack the skin and give off irritating vapours. Therefore, safty spectacles and gloves must wear, avoid contact with skin, and keep stoppers on bottles as much as possible. Procedure 1. Into a test tube pour about 5 cm3 of water and add a spatula-measure of unknown. 2. Cork and shake until the phenol has dissolved. 3. Pour half the solution into another test tube for the reaction with neutral Iron(III) chloride solution. 4. Add about six drops of bromine water to the aqueous phenol. Shaking the test tube after the addition of each drop. 5. Note your observation. Positive results White precipitate and brown colour disappeared means phenol presents. Reaction with neutral Iron(III) chloride solution I could use this reaction as a confirmation test to distinguish phenols. Phenols produce a colour complex with this reagent. Apparatus Safety spectacles Protective gloves Iron(III) chloride solution, 0.5M FeCl3 Test tubes Hazard Warning Both phenol and bromine water attack the skin and give off irritating vapours. Therefore, safty spectacles and gloves must wear, avoid contact with skin, and keep stoppers on bottles as much as possible. Procedure 1. Into a test tube, pour about 1 cm3 of Iron(III) chloride solution. Add sodium carbonate solution, drop by drop, until a trace of the brown precipitate just remains after shaking 2. Add a few drops of neutral Iron(III) chloride solution to the solution prepared in the reaction with bromine water. 3. Note observation. Positive results Violet coloration means phenol presents. ?? ?? ?? ?? Sophie Lam ...read more.

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