To Isolate The Compounds Of Pure Acetylsalicylic Acid

We underwent two different reaction schemes using Dipotassium phosphate (K2HPO4) and Potassium hydroxide (KOH) to isolate the compounds of pure Acetylsalicylic Acid/Aspirin and N-(4-hydroxyphenyl) Ethanimidate/Acetaminophen respectively from Excedrin.
The first reaction scheme to undergo acid-base organic extraction was to isolate the most acidic compound in Excedrin with a weak base, K2HPO4. We isolated the aspirin using aqueous base extraction, with Dipotassium phosphate then treated with HCl to force acidification.
The mechanism for Scheme 1 is shown below: The second reaction scheme we used was also an organic acid-base extraction involving acidification. We used a more basic solvent for this scheme, KOH, to isolate the next most acidic
Since recrystallization is more of a method to purify than a separation method we had to apply the bases. Normally, recrystallization is done by increasing the solubility of a solvent by heating it up, but since we did constant temperature recrystallization we use acidification as our method of recrystallization. The acidification using 6M HCl changed the solubility of our compounds by protonating them. The addition of HCl changed our compounds from soluble ionic salts to less soluble organic compounds. Due to this decreased solubility, our desired compounds of aspirin and acetaminophen precipitated out of the solution into crystals. These crystalline solids can be understood on a molecular level as having their molecules arranged in organized lattice structures. Crystallization provides pure compounds due to the neatness of the lattice formed, all of the molecules in the crystals need to be the same size to form a crystal lattice and impurities tend to be different sizes and shapes on a molecular level. When the crystals form impurities cannot fit in the lattice so they are easy to remove. And all recrystallization needs to occur within a pure compound is just some of the molecules you want to crystallize to nucleate. Nucleation will often happen on its own but there are methods like “crystal seeding” that can encourage
Organic solutes dissolve very well in organic solvents, but not in aqueous solutions. And ionic salts dissolve better in aqueous solution. To utilize this information, we introduced bases that changed our neutral compounds to ionic salts. In water, the salts form of our compounds we produced dissolved better than the pure compound. This change in solubility is what allows the acidic recrystallization to work, because when we put HCl in our solution it reacted with our salts and returned one of our desired products. The desired product, the aspirin or acetaminophen, is much less soluble in water than the salt version of the compound. The decrease in solubility is why the compounds precipitated out and we were able to form the crystals. So, in its salt form the aspirin and acetaminophen are more soluble in aqueous solvents than organic solvents, and in their organic form they are more soluble in organic solvents. These solubility trends are due to the fact that like attracts like so ionic salts, which are very polar, are more likely to dissolve in a polar molecule like water. Organic solutes are more likely to dissolve in the similarly less polar organic