Acetaminophen - lab report PDF

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Description

Acetaminophen Jodyann munroe

Purpose The purpose of this experiment is to produce and purify acetaminophen by first reacting paminophenol with acetic anhydride and undergoing recrystallization to produce a crude acetaminophen. After it is purified by a second recrystallization using ethanol, the percentage yield will be calculated for the pure product produced and its purity will be measured by taking the melting point, IR, and TLC.

Introduction Acetaminophen is a mild analgesic (pain reliever) and antipyretics ( relive fever). Preparation of acetaminophen involves treating an amine with an acid anhydride to form an amide. In this case, p-aminophenol, the amine, is treated with acetic anhydride to form acetaminophen, the amide. During the process to synthesize p-aminophenol the lone pair of electrons on the amine of paminophenol attacks the C=O bond of the acetic anhydride causing it to break. Nitrogen as a positive charge but regains electrons by losing a proton. The negative charge on the oxygen comes back in to reform the C=O bond causing the other C-O bond to break. This results in an amide bond formation and a carboxylic acid by-product. Aside from the chemical reactions that produce the product acetaminophen, isolation and purification techniques also have to be used to

end up with a pure product rather than a crude one. Recrystallization is a technique that will further purify the product. Acetaminophen is not soluble in cold water but it is when the solvent is hot. Any impurities will dissolve in hot water. When everything as dissolved the solution, is cooled. Acetaminophen will crystallize but the impurities will remain dissolved. The acetaminophen can then be characterized by a melting point range IR spectroscopy and TLC.

Procedure

0.5 g of p-aminophenol was weighed and placed in 10 mL vial using a pipet 550mL of water was added, and a spin vane was placed in the conical vial and attached to an air condenser. A sand bath was heated to 120 ℃ a distillation apparatus was assembled, the vial was placed deep in the sand bath, the distillation vial was attached and set on spin until it started to reflux. The vial was kept spinning for 20 min, after 20 mins the magnetic stirrer was washed with ionized water letting it run into the flask. A TLC plate was used, making markings from 1-3. 1 had the p-NH2phenol solution dotted on a line, 2 had the reaction, and 3 had the standard Aceto (Tylenol). The TLC plate was then placed in 0.5% acetic acid in a 250mL beaker. And left to sit until the solvent as nearly run to the top of the plate. After it as ran to the top of the plate the results were

reviewed under UV light. Back to the reaction, the reaction was placed in an ice bath for 15 min and collected by vacuum filtration on a Hirsch funnel. The vial was rinsed with 0.5 mL of icecold water and the mixture was transferred to the Hirsch funnel. The crystals were left to dry for 10 mins through the Hirsch funnel, and the products were transferred to a watch glass to allow to air dry, this process took a few days. And after the few days, the crystals were weighed, percentage yield calculated, and color of the crystals was recorded.

The Acetaminophen as placed a 10 mL Erlenmeyer flask and in another flask 3 mL of a solvent mixture composed of 50% water and 50% methanol with a boiling chip was placed on a hot plate. When the solvent began to boil the hot solvent was added slowly to the acetaminophen using a pipet. Both flasks were then placed on the hot plate to keep them hot and the continuance of adding the boiling solvent to the flask containing the acetaminophen until the solids dissolved proceeded. Once the solid dissolved the contents in the flask were allowed to cool to room temperature. The inside of the flask was scratched with a micro-spatula. The contents were then placed in an ice bath to complete crystallization for 10 minutes. The flask was then transferred to the Hirsch funnel and rinsed with 0.5 mL of ice-cold solvent (50% water 50% methanol). The crystals were dried for 10 minutes and then transferred to watch glass and allowed to air dry. The melting point was then taken and an IR spectroscopy was done.

Data

Chemical

Wt (g)

Melting point

% yield

Starting p-

0.508

N/A

N/A

crude acetaminophen .510

N/A

72.5%

Pure acetamniophen

172

40.0%

aminophenol

.275

Crystal color: cocoa

Calculation

0.508 p -acetaminophen x 1mol/109.1 = 0.00465 theoretical yield

0.510 g crude acetaminophen x 1 mol/ 151.2 = 0.003373 crude acetaminophen

0.275 x 1mol/ 151.2 = 0.0018187 pure acetaminophen

0.003373/0.00465 x100= 72.5% crude acetaminophen

0.0018187/0.00454 x100 = 40.0 % pure acetaminophen

Quality of results

While conducting this experiment it is possible that errors have occurred. One confusion with this lab was understanding the procedures to conduct the lab, there was so much material that it was hard to follow the steps. In terms of completing the section with the TLC plate, there was no prior experience in doing a TLC lab so it was difficult to work as a team to do the TLC plate. A couple of TLC plates were wasted due to not placing the contents on it correctly. Another error was while heating the sand bathe it overheated and the sand had to be left to cool and then reheated again. While measuring the crystals after recrystallization a little bit of the crystals were lost on the weighing scale.

Discussion

In conclusion, the objective was met of this experiment as acetaminophen was synthesized through isolation by recrystallization with the final product characterized by IR spectroscopy, melting point, and TLC. The experimental melting point of the purified acetaminophen product was 172.5 with a 40.0% yield. This result indicates a moderately high purity of the final product. For the TLC plate after looking under the UV light one spot could be seen that corresponds to the acetaminophen that was different from the other spots that were originally marked, conforming the sample was pure. Overall the experiment was successful...