To install StudyMoose App tap and then “Add to Home Screen”
Save to my list
Remove from my list
The primary objective of this experiment was to purify crude acetanilide through recrystallization. Crude acetanilide was synthesized through the acetylation of aniline by acetic anhydride. To achieve a pure compound, the impurities in crude acetanilide, including acetic acid and unreacted acetic anhydride, were removed using activated charcoal, filtration, and recrystallization. The choice of recrystallizing solvent was determined by conducting solubility tests with methanol, hexane, and water. Water was selected as the recrystallizing solvent due to its suitable solubility characteristics. The experiment yielded 1.2 grams of pure acetanilide, resulting in a 40.54% yield.
Recrystallization is a fundamental technique used to purify solid organic compounds.
Compounds obtained from natural sources or chemical reactions often contain impurities, which can include insoluble, soluble, and colored impurities. To obtain a pure compound, these impurities must be separated and removed in a stepwise manner during the recrystallization process.
In this experiment, we aimed to synthesize pure acetanilide by first performing the acetylation of aniline using acetic anhydride.
Verified writer
Proficient in: Chemistry
4.7 (657)
“ Really polite, and a great writer! Task done as described and better, responded to all my questions promptly too! ”
The resulting crude acetanilide contained impurities in the form of acetic acid and unreacted acetic anhydride. To purify the crude acetanilide, we employed a series of techniques, including activated charcoal treatment, filtration, and recrystallization.
Aniline is a clear to slightly yellow liquid with a characteristic odor. It does not readily evaporate at room temperature. Aniline is slightly soluble in water and mixes readily with most organic solvents. Aniline is used to make a wide variety of products such as polyurethane foam, agricultural chemicals, synthetic dyes, antioxidants, stabilizers for the rubber industry, herbicides, varnishes and explosives.
Aniline is prepared commercially by the catalytic hydrogenation of nitrobenzene or by the action of ammonia on chlorobenzene. The reduction of nitrobenzene can also be carried out with iron borings in aqueous acid.
Preparation of Aniline:
C6H5NO2 + 3 H2 → C6H5NH2 + 2 H2O
Acetic anhydride is clear, colorless liquid with a strong, pungent, sour vinegar-like odor, lachrymator. Acetic anhydride is an important solvent and acetylation agent. It is used in the manufacture of acetyl compound, cellulose acetates, acetylizer and solvent in examining wool fat, glycerol, fatty and volatile oils, resins, detection of rosin, in organic synthesis, such as dehydrating agent in nitrations, sulfonations and other reactions where removal of water is necessary. Acetic anhydride is prepared by the carbonylation of methyl acetate. There is a two-stage process for the preparation of acetic anhydride, in which, in a first step, methyl bromide or, preferably, iodide is carbonylated to provide the corresponding acetyl halide, such acetyl halide in turn being reacted with methyl acetate, in a second step, to provide acetic anhydride, which corresponds to the following reaction scheme, in the event that methyl iodide is the starting material:
Step 1:
CH3I + CO → CH3COI
Step 2:
CH3COI + CH3COOCH3 → (CH3CO)2O + CH3I
Among the three recrystallizing solvents – methanol, hexane, and water, water was chosen to be used in the recrystallization of the acetanilide.
Table 1. Solubility of pure acetanilide in various solvents
| Solvent | At Room Temp. | During Heating | Upon Cooling |
|---|---|---|---|
| Water | Insoluble | Soluble | Insoluble |
| Methanol | Soluble | Soluble | Soluble |
| Hexane | Insoluble | Insoluble | Insoluble |
The solubility tests conducted with various solvents—methanol, hexane, and water—revealed that pure acetanilide was insoluble in hexane and water at room temperature. However, it became soluble when heated and returned to an insoluble state upon cooling. Methanol, on the other hand, exhibited solubility throughout the experiment. As a result, water was chosen as the recrystallizing solvent due to its favorable solubility characteristics.
The acetylation of aniline using acetic anhydride resulted in the formation of crude acetanilide. The experiment yielded 7.2 grams of crude acetanilide.
Pure acetanilide was obtained through the recrystallization of the crude acetanilide. From the initial 7.2 grams of crude acetanilide, 1.2 grams of pure acetanilide was isolated.
Theoretical Yield:
Aniline:
2mL x 1.0217 g/mL = 2.0434 g
2.04 g x 1 mol x 135.17 g/mol = 93.13 g/mol
Acetic Anhydride:
3mL x 1.082 g/mL = 3.246 g
3.246 g x 1 mol x 135.17 g/mol = 102.09 g/mol
Therefore, aniline is the limiting reagent.
Percentage Yield:
Percentage Yield = (Actual Yield / Theoretical Yield) x 100
= (1.20 grams / 2.96 grams) x 100
= 40.54%
The experiment resulted in a 40.54% yield of pure acetanilide.
The experiment successfully demonstrated various chemical processes, including the selection of a suitable recrystallizing solvent (water), the acetylation of aniline using acetic anhydride to produce crude acetanilide, and the purification of crude acetanilide through heating, activated charcoal treatment, and recrystallization. The final yield of pure acetanilide was 1.2 grams, representing a 40.54% yield.
For future experiments, it is advisable to explore alternative recrystallizing solvents to compare their effectiveness in purifying acetanilide. Additionally, further optimization of the purification process could potentially enhance the yield of pure acetanilide.
Chemistry Laboratory Report: Acetanilide Recrystallization. (2016, Apr 01). Retrieved from https://studymoose.com/document/organic-chemistry-experiment-4-recrystallization
👋 Hi! I’m your smart assistant Amy!
Don’t know where to start? Type your requirements and I’ll connect you to an academic expert within 3 minutes.
get help with your assignment
