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Identification of an organic unknown

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Introduction

Identification of an organic unknown Aim There are many different chemical tests, which enable us to identify an unknown compound. The only thing known about the compound is that it contains one of the following functional groups: * Alkene * Primary alcohol * Tertiary alcohol * Aldehyde * Ketone * Carboxylic acid * Ester * Phenol I devised a sequence of tests that would identify which of the groups the sample contains. Initially I worked out what tests there are for each functional group, and decided which one to use on the basis that each test should be dependent on the result of the previous test, which helped me to arrange the sequence. Apparatus and reagents * Bromine Water * Test tubes/Test tube racks * Acidified Potassium Dichromate (VI) (K2Cr2O7) ...read more.

Middle

Carefully add a spatula of PCl5 bit by bit. Keep product Dry If positive, steamy white fumes will be given off. Ethanoic acid test Test for all Alcohols Pour 2 cm3 of H into test tube; add equal volume of ethanoic acid. Add 10 drops of H2SO4 and the warm gently. Pour mixture into 400 ml beaker containing 200 ml water. A Sweet smell is given off Test for Primary Alcohols using Jones's reagent (CrO3-H2SO4 in H2O) In a test tube, place 1 ml of acetone in a test tube and dissolve one drop of the unknown compound Add one drop of Jones's reagent and then shake the test tube to mix contents Primary and secondary alcohols react within two seconds. ...read more.

Conclusion

Carboxylic acid present and confirmed, as this test is negative for phenols and alcohols. FeCl3 Test This is the test for Phenols Dissolve 0.50 g of unknown compound in water; add aqueous solution of iron (III) chloride drop-wise There is colour change. Violet colour for phenol and red colour for carboxylic acids 2,4-DNP test This is a test for carbonyls (Aldehydes and Ketones) Add a few drops of 2,4-DNP solution to the unknown compound Label product Carbonyl A yellow or orange precipitate is produced. Confirmation of Aldehyde using Tollen's Reagent Add 2-3 drops of the unknown compound in methanol to 2-3 ml of Tollen's reagent contained in a very clean test tube. Warm gently in a water bath. A silver mirror forms on the side of the test tube from the colourless solution A2 Chemistry - Assessed Practical: Skill P Ibrar Khan 1 ...read more.

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