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Introduction

Identifying of an organic unknown? Identification of an organic unknown? Aim: In this investigation I will get a number of unknown organic compounds. Which I have to identify by using a number of different chemical and physical techniques. The only thing is known about the compound is that it contains one of the functional group: alcohol, aldehyde, ketone, carboxylic acid, phenol and ester. Therefore I devised a sequence of tests that would identify which one of the groups the sample contains. The flow chart below shows the chemical techniques, which I will use to identify the functional group of the unknown. 1: Test with universal indicator. Explanation: Aqueous phenol decolourises bromine water to form a white precipitate of 2, 4, 6- tribromophenol. The presence of OH group in the phenol increases the inclination of the benzene ring to electrophilic attack. The oxygen in the OH group has a lone pair of electron, these can localise n electrons. Because the charge density of the n electron is increased especially in the 2, 4 and 6 arrangement. This is the main cause of the reaction that's takes place only in phenol not in carboxylic acid. 3. Test for carbonyl group Procedure - About 1cm3 of 2, 4 - dinitrophenylhdrazine solution and 1cm3 of ethanol and add several drops of the test substance by using a pipette. ...read more.

Middle

2. They are then placed in water bath and heated; a water bath is used because some chemicals are potentially flammable. 2cm3 sodium hydroxide is then added to each sample in order to hydrolyse the solution. 2cm3 nitric acid is then added to acidify the solution. Silver nitrate is added until no further change takes place. A precipitate is formed in three of the sample solutions. A white precipitate of Silver Chloride (Cl-) soluble in aqueous ammonia would indicate a chloroalkane. A cream precipitate of Silver Bromide (Br-) soluble in concentrated ammonia would indicate a bromoalkane. A yellow precipitate of Silver Iodide (I-) insoluble in ammonia would indicate an iodoalkane. One of the sample liquids should have tested negative for each of the three tests carried out. This sample is the alkane. IDENTIFICATION OF UNKNOWN ORGANIC COMPOUND Introduction This aim of this coursework is to plan and outline a sequence of simple chemical tests that can be used to identify unknown organic compound. These unknown compounds contain one of the following functional groups: Alkenes, Tertiary Alcohol, Aldehyde, Ketone, carboxylic acid, Primary Alcohol, Ester and Phenol. The tests, observations, and inferences will be tabulated and then the risk analysis/safety precautions will be tabulated as well, followed by a flow chart.. ...read more.

Conclusion

Heat the mixture until it boils. On cooling, add 2 ml of hydrochloric acid. If the solution is cloudy, add 2 mL of 95% ethanol. Add I drop of 5% iron (III) chloride. Observe colour change. A positive test will be a distinct burgundy or magenta colour Esters react with hydroxylamine in the presence of sodium hydroxide to form the sodium salt of the corresponding hydroxamic acid. On acidification and addition of ferric chloride the magenta-coloured iron (III) complex of the hydroxamic acid is formed. Therefore Ester is present and confirmed. Risk Analysis Safety precautions Alchohols - (Ethanol) Causes skin and eye irritation Highly flammable Harmful by Inhalation Avoid contact with skin and eyes. Wear eye protection; wash with cold water in the event of contact. Avoid contact with open fire, take car while heating/refluxing, if possible use heating mantle instead of Bunsen burner. Avoid Inhaling gas Ester May act as Irritant Wear safety glasses Ensure there is adequate ventilation H2SO4 Corrosive Liquid can cause damage to skin and eyes See safety precautions on alchohols Use gloves PCl5 Corrosive Always use the fume cupboard Tollens Reagent Highly explosive After the test with Tollens reagent, pour the contents of the test tube into a sink and wash the test tube with dilute nitric acid. ...read more.

This student written piece of work is one of many that can be found in our GCSE Aqueous Chemistry section.