The Separation and Purification of Organic Compounds Sunshine Marie Introduction 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. Methodology 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.
Procedure 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. Extraction 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. 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. Sublimation 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 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. Distillation Simple Distillation A simple distillation set-up was assembled. 100 mL of sandy water and 2 g of copper sulfate was placed on the distilling flask.
Several pieces of broken glass wa added and the heating was started. 50 mL of the distillate was collected when the mixture was boiled. Paper Chromatography: Separation and Identification of Amino Acids Results Solution and Filtration In this experiment, we had the mixture of benzoic acid and sugar. They were divided into two. The first was added by distilled water and the second was added by denatured alcohol. In this, the sugar remained undissolved in denatured alcohol, and the benzoic acid remained undissolved in water.
The component that dissolved in water was recovered by using the technique of filtration and evaporation. We used the process of filtration when we separated a minute of two substances, which really dissolved in solvent while other may be insoluble. Its resulting product are already filtered which means that the mixture is free from impure substances. Extraction Given the mixture of benzoic acid and sugar, we used the process of extraction for the separation of compounds. Different chemicals added the mixture. Thus, resulting to the formation of white precipitate.
The procedure was used for the recovery of a substance from a mixture by bringing into contact with solvent preferentially dissolves the compound. Sugar was dissolved in the mixture of chloroform. The substance in the residue after the chloroform was evaporated is the benzoic acid, its formula is CzH6O2. Sublimation We had the benzoic acid in this process of sublimation. Benzoic acid was covered with a flask filled with cold water and was heated, resulting to the formation of white crystals. Sublimation was used to convert impure organic acd into vapor without passing through the liquid state.
Recrystallization and Decolorization This process was used when solid compounds can be separated by a processed of crystals growth in which impurities retained of the mother liquor. The animal charcoal removed the color of purify the solution. It captured bubbles of gases. It absorbs also the impurities of the solution. Distillation The distillation process is used when separating mixture of liquids with different volatilities. The processes that are involved in the distillation process are evaporation and condensation.
In the experiment on simple distillation, the alcohol is the distillate and the residue is water. We put a broken to prevent ebullition. Paper Chromatography: Separation and Identification of Amino Acids This process is used when component are to be separated and distributed between two phases sample needed: the mobile phase and stationary phase. Below is the result: *Solvent- 7. 7 cm *Solute- 8. 5 cm Calculations: Rf= distance travelled by solute distance travelled by solvent = 8. 5 cm 7. 7 cm Rf = 0. 91 cm Discussion
In the process of Solution and Filtration, the results utilizes the fact that one of the compounds of a mixture of the two substances may readily dissolve in a solvent while the other may be insoluble. We used also the process of evaporation to furnish the soluble substance. In the Extraction that we made, the compound or the mixture is dissolved in one of the two immiscible solvents and then shaken with the other. Equal amounts of the solvent are used, the amount of the compound in each of the two layers had the direct proportion to the relative solubility of the compound in each of the solvents.
The dissolved substance distributes itself between the two immiscible solvents so that the ration of its concentration in each solvent remains a constant for any particular temperature. In the method of Purification, the solid is heated until its vapor pressure is high enough to collect on a cooled surface above the solid. It is concerned about the mechanism of evaporation of molecules of atoms from the solids and with the mechanism of crystal growth from vapors. In the process of Recrystallization and Decolorizzation, formation of crystals. Crystal formation involves three consecutive stages.
The first stage involves removal of impurities which may retard or inhibit crystallization. The second stage is nucleus formation and the third state is the encourgament of growth to visible crystals. This is the process most commonly employed for the separation and purification of solid organic compounds. The impure solid is dissolved in the minimum volume of a suitable solvent. The soluble impurities pass into solution while the insoluble ones are left behind. The hot solution is then filtered and allowed to cool undisturbed till Crystallization is complete.
The crystals are then separated from the mother liquor by filtration and dried. In the process of Distillation, a large temperature difference between boiling points of the components that was purified was required to obtain an efficient separation. The technique of simple distillation is inefficient for the separation of components having temperature difference in boiling points of 30 degrees to 50 degrees. The operation of distillation is employed for the purification of liquids from nonvolatile impurities.
The impure liquid is boiled in a flask and the vapors so formed are collected and condensed to give back the pure liquid in another vessel. The non-volatile impurities are left behind in the flask. The last process is the Paper Chromatography, the paper was carefully dipped into a solvent, which is absorbed into the paper and rises up it. For accurate work the distance moved by the solvent is marked on carefully with a pencil and the distances moved by each ‘centre’ of the colored spots was also measured.
Due to different solubility and different molecular ‘adhesion’ some colors move more than others up the paper, so effecting the separation of the different colored molecules. Conclusion Therefore, the experiments that are were tested in this exercise seemed to met the objectives. We separated the substances to purified the organic compounds, we performed the different operations properly with their possible results and we analyzed and stated the observation based on the results of the different experiments.
I can say that, Organic compounds was derived from natural sources are seldom pure. They are often mixed with other substances, which also occurred with them. The method employed for separation and purification of organic compounds depend upon the nature of the organic compound and the impurities present in it. References Organic Chemistry Laboratory Manual Organic Chemistry with Biochemistry Laboratory Handouts Encarta Premium DVD 2009 scienceclarrified. com
