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Identifying An Unknown Compound

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Chemistry Skill P The purpose of this experiment is to identify an unknown organic compound, henceforth compound X. It is known that the functional group present in compound X is one of alkene, ester, aldehyde, ketone, alcohol, phenol or carboxylic acid. By performing a series of experiments, it should be possible to determine which is the case. Attached is a flow chart, outlining the process necessary to identify the functional group in compound X. Red text denotes an observation, green text a test to be carried out, and black text the conclusion to be drawn from the results. Additionally, the event that no change is observed, and hence no reaction has taken place, is simply denoted by "N/R". Below, one can find detailed descriptions of how to perform the reactions In the vast majority of cases, organic compounds are in the liquid state at room temperature, and this an assumption I have made of compound X during the ensuing instruction. Safety Precautions As we are working with an unknown substance, it is important to take safety in to account. There are some general safety points that are necessary for all tests, and they are as follows: * Lab coats are to be worn at all times, to protect skin from exposure to chemicals. ...read more.


The insolubility of the esters, when compared with the acid and alcohol, may result in the smell being more easily detectable.ii Safety: Sulphuric acid at a concentration of 1 mol dm-3 is corrosive, and irritant. Great care should be taken to avoid exposing the eyes to contact with sulphuric acid, as it causes burns and has an affinity for water.iii Add Aqueous Bromine Chemicals: Aqueous bromine solution. Equipment: Boiling Tube, Bung. Method: Fill the boiling tube half full with aqueous bromine solution, and add one or two drops of compound X. Put the bung on, and gently mix the solution. Watch for decolourisation of the mixture, and a white precipitate, depending on the outcomes indicated on the flowchart. Add neutral iron chloride solution Chemicals: neutral iron (III) chloride solution. Equipment: Boiling tube. Method: Add 1cm3 of compound X to the boiling tube, followed by a few drops of the iron chloride. Watch for the formation of a brightly coloured, often purple complex.iv Warm with acidified potassium dichromate solution Chemicals: Potassium dichromate, sulphuric acid, water. Equipment: Boiling tube, 250cm3 beaker, Bunsen burner, tripod, gauze. Method: Fill the beaker with roughly 150cm3 of water, and heat using the Bunsen burner until it is approaching boiling. ...read more.


Gloves should be worn when working with it, to prevent contact with skin, and caution should be exercised at all times. Warm with Tollen's reagent Chemicals: Silver nitrate, sodium hydroxide (1 mol dm-3), 1 mol dm-3 ammonia solution, water Equipment: 250cm3 beaker, boiling tube, Bunsen burner, tripod, gauze. Method: Fill the 250cm3 beaker with roughly 150cm3 of water, and heat to near boiling using the Bunsen burner, tripod and gauze. Add roughly 5cm 3 depth of silver nitrate solution to a clean boiling tube, and place this in the water bath. Upon adding a drop of sodium hydroxide, you should see a brown precipitate form. Now slowly add drops of the aqueous ammonia until all the brown precipitate has dissolved. Without delay, add several drops of compound X to your solution, and watch for the formation of a silver mirror around the inside of the boiling tube, or a grey precipitate. Either of the two is a positive result. Safety: Silver nitrate is corrosive, and should be handled with care. Ammonia and sodium hydroxide are both bases, and contact with skin should be avoided. It's important to take when disposing of the substances. i Hills Road Study Pack CRS4 pg. 41 ii http://www.chemguide.co.uk/organicprops/esters/preparation.html iii CLEAPSS Hazcard 098 iv Hills Road Study Pack CRS4 pg. 43 v Hills Road Study Pack CRS4 pg. 43 vi http://jchemed.chem.wisc.edu/JCEsoft/CCA/CCA5/MAIN/1ORGANIC/ORG11/TRAM11/C/0362502/MOVIE.HTM ...read more.

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