The Separation and Purification of Organic Compounds
Each year, many thousands of new or unknown organic compounds are prepared or extracted from natural sources such as plants, fungi and animals. In order to identify an unknown organic compound or the components of a mixture of organic compounds, it is necessary firstly to separate and purify the compounds. At any given temperature, a certain number of molecules of a substance in the liquid state have sufficient energy to escape from the surface to create a vapor pressure. This tendency becomes greater as the kinetic energy of the molecules is increased by raising the temperature. When a liquid is heated to a temperature at which the vapor pressure equals that of the surrounding atmosphere, the liquid boils, and this temperature is known as the boiling point. The boiling point of a pure substance at a specified pressure is thus a characteristic property of that substance, and can be used as a criterion of purity and a means of identification. The objectives of this exercise are:
Separate to purify the organic compound.
Perform the different operations properly with their possible result.
Analyze and state the observation based on the result of experiment.
Materials and Apparatus
The chemicals used in the experiment are as follows: benzoic acid, sugar, denatured alcohol, chloroform, acetanilide, copper sulfate, activated charcoal, distilled water, acetone, toluene, glutamic acid and glycine. The apparatus used include funnel, Erlenmeyer flask, separatory funnel, beakers, evaporating dish, water bath, graduated cylinder, stirring rod, watch glass, distilling flask, thermometer, tripod, wire gauze, burner, iron stand, burette, damps, utility damps, condenser adapter, receiver, medicine dropper and filter papers.
Solution and Filtration
A mixture of 1g benzoic acid and 1g sugar was divided into three equal parts. The first portion of the mixture, 25 mL of distilled water was added in a 250 mL beaker. It was shaked vigorously and was filtered. On the second portion of the mixture, 10 mL of denatured alcohol was added. It was shaked vigorously for 5 minutes and was filtered with a new filter paper.
On the third portion of the mixture mentioned, 100 mL of water was added into it. It was heated and was allowed to cool in room temperature and was poured into a separatory funnel. 5 mL of chloroform was added and a stopper was put into it and shaked. The two liquids was allowed to separate into distinct layers. The chloroform was withdrawn into an evaporating dish. The extraction was repeated with a 5 mL of chloroform and the chloroform layers was combined. The evaporating dish which contains the chloroform layers was heated on a water bath.
A 1 g of impure benzoic acid was placed in a dry beaker. The beaker was covered with a flask filled with cold water. It was placed over a low flame.
Recrystalizzation and Decolorization
6 g of impure acetanilide was placed in a 400-mL beaker and was added with 500 mL of distilled water. The mixture was heated while it was stirred until the acetanilide was dissolved. A pinch of animal charcoal was added while it was heated and stirred continuously. It was brought up to boiling point. The hot solution was filtered rapidly through a funnel with fluted filter paper. An equal amount of the filtrate was collected into two separate beakers. The first beaker was covered with a watch glass and was set aside to cool it slowly. The second beaker was placed on a cold water and was stirred while cooling. After the recrystallization was completed in both beakers, the size of the crystals was compared. Lots of crystals was filtered through the same filter paper. It was washed with a little cold water. The crystals was spread on a piece of filter paper and was allowed to dry. The crystals was weighed and was submitted to the instructor....
References: Organic Chemistry Laboratory Manual
Organic Chemistry with Biochemistry Laboratory Handouts
Encarta Premium DVD 2009
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