Xuanyi Li Teaching assistant:
Monday, May 23, Full Report: Synthesis of Aspirin This is posted to help my fellow college students, but please, use this only as a guide and don't copy paste because it's bad.
The objective of organic synthesis is to design the simplest synthetic routes to a molecule. Acetylsalicylic acid, also known as aspirin, is one of the most widely used medications to reduce fever and is also used as a pain killer. It is an acetyl derivative of salicylic acid.
For the reaction to take place, an inorganic acid such as phosphoric acid is used as a catalyst. Be resourceful in this one. A white, milky mixture was obtained when salicylic acid, acetic anhydride and phosphoric acid a catalyst were mixed.
The mechanism of the reaction is: This shows that the oxygen in salicylic acid attacks one of the carbons in acetic anhydride. Also, the mechanism shows how acetic acid was separated from the acetylsalicylic acid.
In the first part of the experiment, heating of the mixture was done and a clear yellow liquid was obtained Table 2. Heating was employed so that salicylic acid would melt and react with acetic anhydride.
On the other hand, water was added after heating not at the start of the experiment. This is to prevent the reaction of acetic anhydride with water at the start of the experiment, if this had happened, no aspirin could have formed.
In this manner, acetic anhydride was decomposed after the formation of aspirin. This addition of cold water is very important in purification and isolation of the crystals from the liquid since aspirin is insoluble in cold water. Purification is needed to eliminate any salicylic acid and acetic anhydride that did not react, as well as the acetic acid product and phosphoric acid.
In this part, purification is not yet complete it was continued on the recrystallization part. Isolation was done through suction filtration, white, sugar-like crystals were obtained. This is quite far from the theoretical yield because it still contains impurities. This data was used to calculate the percent recovery on the latter part of the exercise.
The second part of the experiment was recrystallization. This is the second part of the purification process. Ethanol was used to dissolve aspirin along with the impurities such as salicylic acid and others. Cold water, on the other hand, is used to recrystallize only aspirin, thus, leaving all the impurities behind.
Since aspirin is an ester, it should not be recrytallized from hot water since esters hydrolyses in hot water. After cooling in an ice bath which further facilitates recrystallization and purificationthe mixture was then suction filtered.
The weight of the recovered sample was 2. The calculations for percent yield was shown in Table 6. The percent yield was Perhaps, the sample was not weighed properly or it was weighed when still wet. Certainly, another error occurred.
This could be due to handling problems in suction filtration or drying, etcetera. A classmate just told me the MP range of purified sample, too bad, I forgot to tell my groupmates!
In Table 8, the differentiation of synthesized acetylsalicylic acid from commercially available aspirin was accounted for. The test used in this part was Iodine test, which is a test for the presence of starch since iodine can form a black complex with starch.
After dissolving synthesized aspirin in 2mL water and 1mL iodine solution, a mixture of red-orange liquid and white precipitates was obtained while when commercially available aspirin was dissolved in 2mL water and 1mL iodine solution, a black precipitate in a dark brown to black solution was formed.
This shows that commercially available aspirin contains starch. Other tests that were performed were summarized in Table 7. Acetic anhydride gave a positive result to water solubility test to form acetic acid.
Small esters are actually fairly soluble in water but solubility falls with chain length and hydrophobic parts.
Since aspirin has a hydrophobic aromatic ring, it did not dissolve in water. Having these results, the recrystallized sample was then identified or assumed as acetylsalicylic acid.Reaction of phenol with NaOH and CO2 (Kolbe–Schmitt reaction), then with H2SO4 gives salicylic acid.
Phenol Salicylic acid. On Addition of Acetic anhydride to salicylic acid turn the hydroxyl group into an ester giving Asprin. In order to synthesise the acetylsalicylic acid we need an acetylizing reaction with the salicylic acid, this consists in the esterification with the acetic anhydride, in which the phenoplast group has been converted to its ethanoate ester and the acetic acid therefore been eliminated.
Experiment 1: Synthesis of Acetamides from Aniline and Substituted Anilines Many of the acetylated [CH 3 –C(=O)-] derivatives of aromatic amines (aka anilines) and phenols are acetic acid Both aniline and acetic anhydride are somewhat viscous liquids.
So, simply mixing them together does Reaction mechanism: N CH3 O H3C O O δ-HH δ+ N. Write a complete reaction of succinic acid and acetic anhydride. 2. Write an equation that accounts for the solubility of propanoic acid in aqueous base. 3. Write equations that describe the reaction mechanism for acid hydrolysis of each of the following compounds.
a) Acetyl Chloride b) Acetic anhydride EXPERIMENT 8 (Organic Chemistry II. The limiting reactant in this chemical reaction was salicylic acid, with acetic anhydride present in excess in order to react with any water produced during the reaction of the reactants, and thus improve the yield of aspirin.
The sulfuric acid that was added to the methanol and phthalic acid served as the acid catalyst to begin the reaction. A reflux system was used to provide the heat needed to continue the reaction.
With the knowledge of the starting materials and the conclusion of the product, it was deduced that the reaction was an esterification, which would.