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Identification of an unknown organic compound

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Identification of an unknown organic compound Aims: The aim of the identification experiment is to use a variety of tests to ultimately go to one functional group to identify an unknown organic compound. It could be one of the following: * Alkenes * Primary alcohol * Tertiary alcohol * Aldehyde * Ketones * Carboxylic acid * Ester * Phenol I will take each of the supplied functional groups and talk about them generally and identify a test which will be most suitable to identify whether that functional group is present in the unknown organic compound we are provided with. If tests need to be taken to see if oxygen, carbon dioxide or hydrogen gas has been given off, we will do the following: * Hydrogen - is present if we light a splint and put it in the test tube and it goes out with a squeaky pop. * Oxygen - is present if we light a wooden splint and blow it out and put it in the test tube and it rekindles. * Carbon dioxide - is present if when bubbled through lime water- it goes cloudy. ...read more.


If the test is positive the solution a silver mirror will form. * Fehling's solution - Mix 0.5cm3 of Fehling's solution A with 0.5cm3 of Fehling's solution B in a small test tube. Add 2 or 3 drops of the unknown organic compound and heat the tube. If the test is positive the solution will go from blue to red. I have decided to use the Fehlings test and the tollens reagent as these two tests will make sure it has a aldehyde present we can eliminate that to find out whether the unknown compound is a ketone . Fehlings test, in the the blue Cu2+(aq) complex solution forms a brown precipitate of copper(I) oxide Cu2O(s). The aldehyde reduces the copper ion and in the process gets oxidised to a carboxylic acid. Apparatus needed: * Fehlings solution A * Fehlings solution B * Test tube * Unknown organic compound * Hot water bath * Beaker For tollens * Silver nitrate solution * Sodium hydroxide * Ammonia solution * Water bath * Unknown organic compound When these two have been used and we have found out that it is not an aldehyde we will be use the 2-4-dinitrophenylhydrazine test to test positive for a ketone as aldehyde has been eliminated Equation for tollen's : RCHO + 2{Ag(NH3) ...read more.


is substituted to give 0 base + water The reason why phenol produces water is because it is partially sparingly soluble in water. Therefore phenol ionizes slightly in water so the -OH bond breaks to form a hydrogen ion and phenoxide ion. The bond is more readily in phenol than water so phenol is more acidic than water (chemistry 2 endorsed by OCR page 17 in the blue box) The identification test I will use for this will be using ferric (iron iii) chloride. I will add 5 drops of ferric chloride; add 2 drops of substance and 2 drops of water. If the test is positive the color of the solution will turn purple. The Iron(III) ions form strongly coloured complexes with several organic compounds including phenol. The colour of the complexes vary from compound to compound. You get an intense violet-purple solution formed when phenol is added to the solution. (http://www.chemguide.co.uk/organicprops/phenol/other.html) Apparatus needed: * Ferric chloride * Test tube * Water * Unknown organic compound Other tests I could have used would have been adding the substance to sodium hydrogen carbonate. If it doesn't dissolve this would have suggested a phenol was present. Flow chart of tests ?? ?? ?? ?? 13c2 1 ...read more.

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