January 26, 2023

This video serves as a brief overview of the experimental flow in Practical 2 of CHM 181, at the University of Pretoria.

Good day students i’m lori lee kenz welcome to part two of the synthesis of aspirin this part we’re going to look at the purity of our aspirin we’re going to determine whether all of our salicylic acid has formed aspirin we’re going to do this by using a tlc plate and tlc is short for thin layer chromatography experiment we’re going to do this by adding a standard

Of aspirin so where we know that is exactly aspirin and nothing else in it our homemade aspirin and then our starting reagent of salicylic acid and we’ll see how they compare we now have our aspirin synthesized or at least what we hope is aspirin so now we need to dry on tlc plates we’re going to dissolve some of our aspirin in ethanol and then we’re going to

Use the capillary tube to spot them on our tlc plate so now we need to start spotting rtlc plate with our three reagents the standard of salicylic acid our standard of aspirin and our homemade aspirin we’re going to take our standard aspirin which has already been prepared for us we’re going to use a capillary tube so this is a glass tube which is extremely

Thin to make sure that we only have a really thin spot on our tlc plate so we just dip it into our solution and then we need to make sure that the capillary tube is upright when we spot it so you’ll see there’s a little dot that forms and we’re going to do that twice to make sure we’ve got enough solution on our tlc plate so now we’re doing our homemade

Aspirin and this is salicylic acid before we run the tlc plate we’re going to use a uv light to confirm that we have spotted everywhere you can see that there are dots at each one of them the salicylic acid is a bit lighter than the rest you both will be able to see it when we run the tlc tray so now we need to start running our tlc plate but before we can

Do that we need to make sure that the beaker with our eluent is fully saturated okay so now we need to make sure that the tlc plate is dry before we have a look at it under the uv light again so here you can see the three different dots so i’ll circle them so this one we’ve clearly got a circle over there in here this is what you’re going to use to identify

Whether our synthesized aspirin formed aspirin completely or whether it still has salicylic acid in it now that you have the data from our tlc plate you can determine the purity of our aspirin if there are more than one spot in our homemade aspirin especially one corresponding to a salicylic acid you can determine whether all of our salicylic acid has reacted

To form aspirin or not if there are any points that do not match the salicylic acid all the aspirin standards that we’ve used that probably means that the sample is impure you’re now going to use this data and determine whether our homemade aspirin is pure or not so this is an experiment that you can also do at home you’ll find more information on this in the

Chromatography experiment done by a different group of scientists i hope you’ve learned something today and enjoy the rest of your day

Transcribed from video
Synthesis and Analysis of Aspirin (experiment 2) By UP Chemistry Department