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The Preparation of Acetaminophen (Paracetamol) with Thin Layer Chromatography (Tlc) to Monitor the Reaction.

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Experiment 3: The preparation of acetaminophen (paracetamol) with thin layer chromatography (TLC) to monitor the reaction.

Abstract:

This experiment is to demonstrate the preparation of paracetamol and its properties. Reflux and filtration of 4-aminophenol and acetic anhydride formed the crude sample. Further analysis of dry white crystals were used to give quantitative measurements and a percentage yield of 46% was obtained. The overall conclusion is that the acetic anhydride reacted with the –NH2 group.

Materials and Methods:

1. We weighed out (on a top-pan balance) 4-aminophenol (about 11.0g) in a weighing boat and transfer the powder to a 250cm3 round-bottomed flask (RBF) using a powder funnel. 2. Then recorded the amount …show more content…

-Sample + Ethanol= Colourless solution

FeCl3 was then added to this solution and a positive colour change was seen, as it turned green

-Sample + Ethanol + FeCl3 = Dark Green solution

This was then repeated using Salicyclic Acid instead of the sample to give a reference material as it will give a positive test for a phenol.

-Salicyclic Acid + Ethanol = Colourless solution

-Salicyclic Acid + Ethanol + FeCl3 =Purple solution

The positive colour change from colourless to dark green of the sample means that the phenol group is present in the sample. Therefore indicating that the acetic anhydride has reacted with the amino group.

3. Determine the melting point and record the infrared spectrum of the dry solid.

Melting Point:

The melting point of sample obtained is: 1680C

Literature Value: [1]: 169-1720C

Fig 1.1-Infrared Spectra of Paracetamol:

The infrared spectrum of paracetamol shows the appearance of a new peak at 1561 – 1650cm-1 this represents the carbonyl group from the acetic anhydride, meaning that paracetamol has been formed. The –OH peak is still present at 3109 – 3319cm-1 this shows that the phenol group is still attached to paracetamol. From the infrared spectra you can also see that the –NH2 group has disappeared. This is as it has been selectively acetylated by acetic anhydride to form paracetamol.

4. TLC Plate analysis and Rf values of important spots.

Fig 1.2-Thin Layer Chromatography of Student samples 1 and

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