Recrystallization: Solvent and Solubility
RECRYSTALLIZATION OF ACETANILIDE
ABSTRACT
Recrystallization is the primary method for purifying solid organic compounds through the differences in solubility at different temperatures. In this experiment, a suitable solvent was first determined. Acetanilide was produced by acetylation of aniline with acetic anhydride. The crude acetanilide was dissolved in a solvent in a heating water bath. The hot solution was filtered and the filtrate, cooled slowly in an ice bath as crystals started forming out. As the compound crystallizes from the solution, molecules of other compounds were excluded from the crystals to obtain pure acetanilide.
INTRODUCTION
Recrystallization, referred to as the second crystallization, is a method in which two crystallization processes are performed. It is a process of dissolving the solid to be crystallized in a hot solvent or solvent mixture and then cooling the solution slowly. This technique can be used for large or small quantities of materials, and is usually very effective and efficient. The most important aspect of the recrystallization technique is the selection of the solvent. A large number of solvents are commonly used for recrystallization of organic compounds. Among these are water, ethanol, ethyl ether, methanol, and hexane to name just a few. A solvent, which works beautifully for one recrystallization, may be totally unsuitable for purification of a different compound - the choice for recrystallization solvent is made on a case-by-case basis. This is because of the variation of solubility of different organic compounds in these solvents. A desirable recrystallizing solvent would increase the solubility of the solute as the temperature rises. Aniline is a clear to slightly yellow liquid with a characteristic odor. It is slightly soluble in water and mixes readily with most organic solvents. When exposed to light and air, it slowly changes color. It darkens because of atmospheric oxidation of an impurity usually
ABSTRACT
Recrystallization is the primary method for purifying solid organic compounds through the differences in solubility at different temperatures. In this experiment, a suitable solvent was first determined. Acetanilide was produced by acetylation of aniline with acetic anhydride. The crude acetanilide was dissolved in a solvent in a heating water bath. The hot solution was filtered and the filtrate, cooled slowly in an ice bath as crystals started forming out. As the compound crystallizes from the solution, molecules of other compounds were excluded from the crystals to obtain pure acetanilide.
INTRODUCTION
Recrystallization, referred to as the second crystallization, is a method in which two crystallization processes are performed. It is a process of dissolving the solid to be crystallized in a hot solvent or solvent mixture and then cooling the solution slowly. This technique can be used for large or small quantities of materials, and is usually very effective and efficient. The most important aspect of the recrystallization technique is the selection of the solvent. A large number of solvents are commonly used for recrystallization of organic compounds. Among these are water, ethanol, ethyl ether, methanol, and hexane to name just a few. A solvent, which works beautifully for one recrystallization, may be totally unsuitable for purification of a different compound - the choice for recrystallization solvent is made on a case-by-case basis. This is because of the variation of solubility of different organic compounds in these solvents. A desirable recrystallizing solvent would increase the solubility of the solute as the temperature rises. Aniline is a clear to slightly yellow liquid with a characteristic odor. It is slightly soluble in water and mixes readily with most organic solvents. When exposed to light and air, it slowly changes color. It darkens because of atmospheric oxidation of an impurity usually