Pre-Lab
Analgesic drugs are known for reducing pain, while antiseptic drugs reduce symptoms such as fevers and swelling. However, some of these drugs can reduce both illnesses. To obtain a pure compound in these drugs, the scientist needs to separate the desired compound by taking advantage of the different physical and chemical properties. Such as; different boiling points, melting points and their solubility properties.
To do this a chemist can also asses the differences between acidic and basic substances when they are added to water soluble mixtures. Within this current experiment I will asses the pharmaceutical preparation of Panacetin, by using it’s solubility along with other organic molecules.
We know that Panacetin is made up of sucrose, aspirin and some other unknown substance. We know the substance has to be Phenacetin or Acetanilide. To help solidify our reasoning, we need a % recovery of 8-12% sucrose, 35-45% aspirin and 45-55% unknown. Sucrose for example is insoluble in dichloromethane, while aspirin is soluble in CH2Cl2, but not in H2O.
The organic compound sodium hydroxide will convert aspirin to Sodium Acetylsalicylate, which is soluble in water. Phenacetin and Actinilide are soluble in CH2Cl2, but not water. Actinilide and Phenacetin can be converted to salts by Sodium Hydroxide. The drawn out calculations on the last page will show this process being completed. Phenacetin and Acetinilide being broken down into salts helps us express that, Panacetin and dichloromethane should dissolve the aspirin and our unknown substance, but leave our sucrose behind that can be extracted by filtration.
Aspirin can then be dissolved by an aqueous solution, HCL and dichloromethane. Which will then be converted to a salt. Once we dissolve the salt, our unknown solution will be left behind. The drawn out calculations on the last page of the lab will also show all the organic molecule’s, molecular structures. Problem: Is the composition of Panacetin as stated on the label correct? Hypothesis: I believe that the label is correct. Because our bodies have the ability to use Acetaminophen, to convert Acetanilide and Phenacetin.
Without that ability or bodies would have shown us bad symptoms, as soon as we consumed Panacetin. Procedure: Sucrose Separation Accurately weigh 3g of Panacetin, put in 125ml beaker Add 50ml of CH2Cl2 to 125ml beaker Stir mixture until its dissolved, use an already weighed filter paper to filter the mix using gravity. Weigh sucrose after it dries and try to retain as much as possible!!! Aspirin Separation Transfer to funnel and extract by using two, 25ml portions of aqueous 1M Sodium Hydroxide. You will need to separate containers and label each.
Then return the dichloromethane to separate funnel before next extraction Combine the 2 aqueous extracts into the same container and save the dichloromethane layer. Add 10mlof 6M HCL SLOWLY, while stirring to the combined aqueous extracts Test the Ph level and add more acid if needed to reach a Ph of 2 Cool with ice bath until the solution is at least 10 degrees centigrade, and the use a vacuum to filtrate Unknown Separation Use filter flask attached to a trap and aspirator to evaporate the solvent (CH2Cl2) Stop when the solid is the only thing remaining, or when no more evaporation is occurring
Observation
During the first portion we were able to weigh exactly 3. 00g of Panacetin. Once I added CH2Cl2, I saw the white solution become a milky, or light colored gray liquid form. As we stirred the Panacetin dissolved slowly, and the fog like substance remained. After the filtrate was separated from the solution, I was left with a white, powdery substance called sucrose. We set the damp sucrose aside and 24hrs later, we took its mass.
Later on during the aspirin separation, I saw two separate liquids form, from one solution. Aspirin was filtrated out of the solution once we dded NaOH. Thus, leaving us with a layer of aspirin and another layer of CH2Cl2. During the unknown separation, the aspirator evaporated the the solvent. But by cooling the substance we were able to recover the dichlormethane and then re evaporate until I only saw the solid substance remain. Although we succeeded with losing barely any substance, as I will prove later in the calculations section.
Analysis
To determine if the label reads correctly, we need to find all of our percent recoveries. Once again to try and illustrate this, we need to use all of our background knowledge. Acetanilide and Phenacetin are not soluble in H2O, but are soluble in CH2Cl2. They also cannot be converted into salts by sodium hydroxide. Since the two possible unknowns cannot be dissolved in water, I can mix Panacetin with CH2Cl2.
This, dissolves the aspirin and the unknown components, leaving us a powdery looking substance called sucrose, that will need to be filtered. I measured out 3grams of Panacetin and then mixed it with CH2Cl2. Then after the filtration I was left with sucrose isolated, and then a substance containing aspirin and the unknown all mixed in with dichloromethane. Our data shows that we had a total of . 92g of sucrose. However, once we subtract the filter paper we only have . 40g of sucrose. Now I had another mixture that needed to be filtered out. In order to get aspirin separated from the solution, I needed to use NaOH.
Once we extracted this solution, we were left with two different layers. An organic layer and an aqueous layer. The aqueous layer contained sodium acetylsalicylate with water. By adding HCl to the substance, we can now filter the precipitated aspirin. After the paper was dried overnight we took its mass and found that we had contained 1. 17g of aspirin. Now we had to get our unknown substance out of the organic layer that was mixed with dichloromethane. To do so, we evaporated the liquid, cooled it, to recover the dichloromethane and then let it evaporate over night.
Once the evaporation was complete I weighed the mass of what should be the unknown, and came up with 1. 90g, without subtracting the filter paper. Once the paper is subtracted, the mass of the unknown is 1. 38g. I then took the total mass of the compounds (aspirin, sucrose & unknown) and came up with a total of 2. 95grams. My next step led me to calculating the percent of each organic compound in Panacetin. My percent sucrose was . 40/2. 95X100=13. 559%. Percentage of aspirin was 1. 17/2. 95X100=39. 661%. And finally, my percent of unknown was 1. 38/2. 95X100=46. 779%.
I found my total percent recovery by taking my total mass recovered, divided by mass of Panacetin, all multiplied by a factor of 100. Thus showing me that 2. 95/3. 00X100=98. 33% was recovered. All of my percent recoveries were within the recommended ranges. Aspirin fell right into the middle of the recommended marks. 35-45% was the label’s required amount. And my aspirin’s 39. 661% recovered, is telling me that is an accurate recovery. 45-55% was what the label preferred unknown amount, and I recovered 46. 779%. Which isn’t perfect, however, its a high enough A to say that the label is also accurate.
Unless, I made the same mistake that the original chemist made. Now sucrose is a slightly different scenario. Sucrose was desired to be at a % recovery rate of 8-12%. However I recovered 13. 559%. So out of the desired range, but only slightly. This was probably caused not by a mathematical error, but most likely by myself. I more than confident that my error came from not stirring the Panacetin with CH2Cl2, until the Panacetin was dissolved. Time was permitting me from being able to completely dissolve the Panacetin. So I decided that I was close enough to being 100% dissolved.
I did once last stir and looked into the substance. Everything looked to be dissolved, however my percent recovery proves to me that I was very close, just not close enough to get a within the desired sucrose range. Not stirring my Panacetin until it dissolved also caused me to not be able to completely recover my desired 3. 00grams of Panacetin. This is why my total mass recovered is only 2. 95g, instead of 3. 00g. Thus giving me 98. 33% rather than 100% recovery.
Conclusion
Finishing the lab, and calculating my percent yields, I am more than confident in saying that my hypothesis was correct. My aspirin recovery was right in the middle of the recommended 35-45% rate with 39. 661% recovered. My unknown recovery was established with a 46. 779% recovered. Which is right in the mix of the recommended amount (45-55%). The only reason why I received a total recovery rate of 98. 33% instead of 100%. Was because I didn’t mix the Panacetin with CH2Cl2 well enough. Therefore I received a recovery rate just outside the recommended range of 8-12% with 13. 559% recovered. If I had mixed the Panacetin a little more I would have probably made the range, instead of missing it by 1. 59% (13. 559-12. 000).
Never the less, I believe that 98. 33% recovered is a high enough A, to say that the problem above, is not a problem at all. The label on Panacetin is correct. By adding 6M of HCl to sodium acetylsalicylate, we know that a chemical reaction occurred because the HCl will cause the solution to donate its OH ion that was transferred from aspirin, when we added NaOH to it earlier in the experiment.
We know that the OH ion will be transferred because our prior knowledge of acids, bases vs. strong and weak acids and bases. I know that HCl is very strong acid and that it can produce maximum concentration of H+. Since sodium acetylsalicylate can be ionized in water, it will give up its OH ion to the other mixture thats inside the solution (aspirin).
This is exactly the mistake I made when performing this lab. Not stirring allowing the Panacetin to dissolve caused me to receive a percent recovery that was 1. 559% to high. However, the percentage that one would be above or below the 8-12% desired amount, changes based off of how much Panacetin hadn’t dissolved.
By failing to mix the aqueous and organic solutions completely your percent recovery rate of aspirin would be effected. Because you wouldn’t have been able to clearly separate the two layers, even with vacuum filtration. So when your aspirin dried and you measured out the mass, it would probably be to low due to the amount of CH2Cl2 or unknown thats still residing in the aspirin. Thus, causing your percent recovery to be out of the desired range of 35-45%. If I were to have made this mistake I believe that my overall recovery rate of the unknown portion of Panacetin would have to be effected negatively.
Because
This would make our Ph level a lot higher than 2. So in theory I believe that we would have a more basic substance rather than an acidic one. Because HCl is what causes sodium acetylsilylate to donate the OH ion. If NaOH were to replace it, then the proton donation would never occur. If this mistake were to have occurred, the litmus paper making our solution’s Ph level 7, would make our aspirin recovery rate impossible to get. Because being at pH of 7, the solution isn’t acting as base due it already proton donating itself.
