Qualitative organic analysis - Introduction The aim of this...

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Introduction The aim of this experiment is to characterize the structures of organic compounds by qualitative organic analysis. Qualitative organic analysis is used to establish the presence or absence of particular organic compounds or functional groups in an unknown sample. In this experiment, qualitative organic analysis was used to find out which organic compound was alkene, which one was alcohol, which one was ketone or aldehyde. This method is to determine the structure of an unknown organic compound. First of there are two steps for alkene for bromine and potassium permanganate test. According to the lab manual, most alkenes react quickly and smoothly with a dilute solution of bromine to form a colorless solution. When alkenes reacts with a solution of potassium permanganate, the product will change from purple to clear with some muddy brown precipitate. These two reactions are an example of an addition reaction resulting from the conservation of one pi bond and one sigma bond into two sigma bond. The electrons of the pi bond are exposes and are particularly susceptible to electrophiles such as bromine and potassium. However, each reaction differs in the stereochemistry as a result. Following for the test of alcohol, a chromic acid test was used to test for the existence of alcohols using Jones reagent. This reaction can be seen tested positive when the initial color orange indicative of Cr +6 is changed to a blue/green precipitate or suspension (Cr +3 ). The primary and secondary alcohols is oxidized via the reagent to carboxylic acids; however, the tertiary cannot react with chromic acid because they do not have ahydrogen atom bonded to the central carbon. For the next part, the amines add to the carbonyl group to give compounds known as imines. These imines could be used to characterize the identify of unknown aldehyde or ketone via formation yellow, orange, or reddish precipitates
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while alcohols do not react. The last one, the unknown was added to 2,3-dimitrophenylhadryzine to indicate the carbonyl group since it produce nice crystals with well-defined melting points. The mechanism of the reactions of alkenes with bromine: The mechanism of the reactions of alkenes with potassium permanganate: The mechanism of the reactions of primary alcohol with Jones reagent: The mechanism of the reactions of a ketone with 2,4-DNP: Experimental Section Flow chart Part 1: Test for an alkene Br 2
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+ 1mL methylene chloride + 3 drops unknown IA + 4 drops of 1M Br 2 + Agitate + Time, precipitate, texture, color + 1mL methylene chloride + 3 drops of unknown IB + 4 drops 1M Br 2 + Agitate + Time, precipitate, texture, color + 1mL methylene chloride + 3 drops of unknown IC + 4 drops 1M Br 2 + Agitate + Time, precipitate, texture, color Potassium permanganate + 1mL methylene chloride + 3 drops of unknown IA
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