Recrystallization

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RECRYSTALLIZATION
Lem Therese D. Delos Ama, Glenn Dale M. Desquitado, John Carlos M. Drapesa, Arianne Valerie B. Escritor, Elisha Ellis R. Esteva
Group 4 2B Medical Technology Organic Chemistry Laboratory

ABSTRACT
In this experiment, acetanilide was used as the pure organic compound. Acetylation of aniline and acetic anhydride yields the crude product or crude acetanilide. The crude acetanilide was purified by dissolving it in hot water and then the solution was cooled slowly by placing in an ice bath. The yielded crystals were pure acetanilide since molecules of other compounds present in the crude acetanilide were excluded from the growing crystal lattice. Lattice is a fixed and rigid arrangement of atoms, molecules or ions. The melting point of the pure acetanilide was then determined by placing it in a capillary tube then immersed it to the oil bath with a thermometer and was monitored. The percentage yield calculated was 37.04%.

INTRODUCTION
Recrystallization is the simplest and most widely used operation for purifying organic solids that differ in their solubility at different temperature. The objectives of this experiment are to purify an impure solid, and calculate its percentage yield. It is a way of effective recovery of a substance mixed with another to produce a pure compound. With their differences in solubility you can separate them by dissolving the mixture then filter out the impurities in the process.

In this experiment, aniline is the primary compound used to acquire Acetanilide, which is our product. Anilineor phenylamine(IUPAC name) with a formula of C6H5NH2, is an odorless, oily, poisonous benzene derivative.

Figure 1. Structure of Aniline

Acetanilide is the product of this recrystallization. Acetanilide or N-phenylacetamide (IUPAC name) with a formula of C6H5NH(COCH3) is produced by adding acetic anhydride with Aniline.

Figure 2. Structure of Acetanilide

The experiment’s objectives are the following:
* Synthesize acetanilide by the acetylation of aniline
* Purify crude acetanilide product by recrystallization

EXPERIMENTAL
A. Compounds tested (or samples used)
Acetanilide

B. Procedure
A corn-grain sized amount of pure acetanilide was deposited into three (3) different test tubes. Distilled water was then added to one test tube, hexane to another, and methanol to the last. The test tubes were shaken and placed in a water bath for 1-5minutes. After heating, the test tubes were placed immediately to an ice bath. The solubility of the pure acetanilide in the different solvents at varying temperature was noted. This process will determine the appropriate and the best solvent that will yield pure acetanilide through the acetylation of aniline and acetic anhydride.

Figure 3. Filtration of the pure acetanilide and the expulsion of the impurities In an Erlenmeyer flask, 2mL of aniline was added with 20mL of distilled water then slowly added with 3mL of acetic anhydride. The flask was put in an ice bath to hasten the crystallization of the solution. When the crystals were fully formed, the solution was filtered to obtain the formed crystals, which will be the crude acetanilide. After filtering, the crystals were dried by pressing with filter paper that will sip the remaining liquid. This process is the first crystallization on the experiment.

Figure 4. The pure acetanilide with the thermometer in the melting point determination.

Figure 5. The mixture of aniline mixed with acetic anhydride forming the crude acetanilide When the crude Acetanilide was completely dry, 20mL of water was added which is the chosen recrystallizing solvent. The solution was subjected in a water bath until all the solid dissolves. Since the solution became colored, activated charcoal was used to remove the colored impurities and was heated again. After heating, the solution was filtered immediately while it was still hot and the filtrate was placed on an ice...
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