Extraction and Evaporation Recrystallization and Melting Point Measurement
Chem 231: Organic Chemistry Lab
EXPERIMENT #2 and #3
Extraction and Evaporation
Recrystallization and Melting Point Measurement
PURPOSE:
1. To the components of a simulated pharmaceutical preparation, Panacetin, and identifying the unknown component of the mixture through extraction and separation methods.
2. To learn how to purify by recrystallization, how to dry them and how to obtain a melting point.
PRECAUTION: ACETANILIDE AND PHENACETIN ARE EYE AND SKIN IRRITANTS. Minimize contact with your unknown compound.
THEORY:
In this experiment, Panacetin, a pharmaceutical preparation will be separated from its components by making use of their solubilities and acid-base properties. Panacetin contains aspirin, sucrose and an unknown component that may be either acetanilide or phenacetin. Of the three components, only sucrose is insoluble in the organic solvent dichloromethane (CH2Cl2 or methylene chloride). The insoluble sucrose can be filtered out if Panacetin is dissolved completely in dichloromethane by gravity filtration or centrifugation leaving the soluble aspirin, acetanilide and phenacetin in the solution.
Although the acetanilide and aspirin are both quite insoluble in water at room temperature, the sodium salt of aspirin is very soluble in water but insoluble in dichloromethane. Aspirin, which is a strong acid can be converted to the salt, sodium acetylsalicylate by extraction with an aqueous solution of sodium bicarbonate . This salt will migrate from the dichloromethane layer, in which it is insoluble, to the aqueous layer, in which it is soluble. The unknown component will stay behind in the solution and can be isolated by evaporating the solvent from the dichloromethane solution. Adding HCl to the aqueous solution restores aspirin as an insoluble white solid.
In the third experiment, the identity of the unknown component of Panacetin will be purified. Purification is necessary because the separation procedure
EXPERIMENT #2 and #3
Extraction and Evaporation
Recrystallization and Melting Point Measurement
PURPOSE:
1. To the components of a simulated pharmaceutical preparation, Panacetin, and identifying the unknown component of the mixture through extraction and separation methods.
2. To learn how to purify by recrystallization, how to dry them and how to obtain a melting point.
PRECAUTION: ACETANILIDE AND PHENACETIN ARE EYE AND SKIN IRRITANTS. Minimize contact with your unknown compound.
THEORY:
In this experiment, Panacetin, a pharmaceutical preparation will be separated from its components by making use of their solubilities and acid-base properties. Panacetin contains aspirin, sucrose and an unknown component that may be either acetanilide or phenacetin. Of the three components, only sucrose is insoluble in the organic solvent dichloromethane (CH2Cl2 or methylene chloride). The insoluble sucrose can be filtered out if Panacetin is dissolved completely in dichloromethane by gravity filtration or centrifugation leaving the soluble aspirin, acetanilide and phenacetin in the solution.
Although the acetanilide and aspirin are both quite insoluble in water at room temperature, the sodium salt of aspirin is very soluble in water but insoluble in dichloromethane. Aspirin, which is a strong acid can be converted to the salt, sodium acetylsalicylate by extraction with an aqueous solution of sodium bicarbonate . This salt will migrate from the dichloromethane layer, in which it is insoluble, to the aqueous layer, in which it is soluble. The unknown component will stay behind in the solution and can be isolated by evaporating the solvent from the dichloromethane solution. Adding HCl to the aqueous solution restores aspirin as an insoluble white solid.
In the third experiment, the identity of the unknown component of Panacetin will be purified. Purification is necessary because the separation procedure