Reearch Paper

Recrystallization Estopace, Edgie1, Polintan, Clarisse K. prof Edgie Estopace, School of chemical substance Engineering, alchemy and Biotechnology, Mapua Institute of Technology Clarisse Polintan, CHM145L/A21, School of Chemical Engineering, Chemistry and Biotechnology, Mapua Institute of Technology ABSTRACT This experiment is all or so identifying the appropriate solving for recrystallization and technique and to use the recrystallization technique in ablutionary a consentaneous sample. Most organic substances ar unclean and lead techniques in order to purify a sample. One of these techniques to make an im clean sample pure is by recrystallization.This experiment includes the determination of a undecomposed declaration for recrystallization for composites such as acetanilid, acetamide, aspirin, benzoic acid, naphthalene, and sucrose, for closures such as pissing supply, ethanol, benzene, and ethyl group acetate. Also pure acetanilide is achieved. here ar five stud y steps in the recrystallization solve dissolving the solute in the resoluteness, performing a gravity filtration, if necessary, obtaining crystals of the solute, collecting the solute crystals by vacuum filtration, and, finally, drying the resulting crystals giving us the pure sample of the compound.The best answer employ for each of the compounds listed and the portion recovery of the cutting acetanilide. The physical properties of the compound were in like manner determined. INTRODUCTION Differential solubility is defined as the differences in the amount of solid that can be concluded in an appropriate reply as affected by variations in temperature. Solubility is inversely proportional to its temperature, since almost solids have solubilities that are visit in liquifiable firmness of purposes at low temperatures.Feature hold Relative RatesFree-Radical BrominationDifferences in solubilities are sometimes apply in the process of obtaining pure compounds by dissolv ing the solid in tropical solvent and allow the un break apartd impurities to be pick uped off. The filtrate would thusly be cooled down and recrystallized as a purer compound. There should be differences in the solubilities of the solid and the impurities in order for the recrystallization to be effective. Recrystallization only works when the proper solvent is being used.The appropriate recrystallization solvent should dissolve the entire compound at heights temperature, dissolver very little or none of the compound at low temperature, have different solubilities for the compound and the impurities, have a boiling point below the melting point of the compound, have relatively low boiling point, be inert with respect to the compound, and be relatively inexpensive. MATERIALS AND METHODS The first part of the experiment required the students figure out which solvent is appropriate for recrystallization technique. Approximately 0. 10 grams of acetamide was weighed and placed ins ide a test tube.The acetamide was thusly dissolved in two millilitres of glacial weewee. The solubility behaviour was hence observed. If the acetamide did not dissolve, the mixture was and so boil and its solubility behaviour was again observed. These steps were thence repeated but with cold ethanol, benzene, and ethyl acetate as the solvent instead of water. The above procedures were repeated, however, the students used different solutes this time for observation. The compounds used coterminous were acetanilide, aspirin, benzoic acid, naphthalene, and sucrose, followed by the recording of data.The countenance part of the experiment tackled the recrystallization process using impure acetanilide and water as a solvent to obtain a pure sample of acetanilide. This part used the acrid sombreness Filtration Set-up first, followed by the vacancy Filtration Set-up. The calorific Gravity Filtration Set-up included the pursual apparatuses a stemless funnel, a fluted ashless filt er makeup, an Erlenmeyer flask, a hot water lavatory, and a hot plate. The Vacuum Filtration Set-up included water suction, rubber tubing, a 500ml Erlenmeyer flask, a rubber stopper and a porcelain Buchner funnel.Other apparatuses used include the Thomas-Hoover break up Apparatus, micro test tubes, a test tube rack, capillary tubes, a beaker, and an oven. First, approximately 100 mL of water was heated and approximately 3. 50 grams of natural acetanilide was weighed. The impure acetanilide was then dissolved in 30 mL of water using 150-ml beaker. The mixture was slightly boiled using a hot plate. When the mixture started to boil, 2-ml portions of the previously heated water was added until the white solid had dissolved. A temperature of 90 C was primary(prenominal)tained. The total intensity level of the water used was then recorded.A small amount of activated carbon was then added. Using the hot gravity filtration set up up, the solution was poured into the fluted filter p aper that was in the stemless glass funnel. The filtrate should then be colourless, if not more activated carbon was added and the filtration process was repeated. The flask was then removed from the hot plate and the residue was discarded. FIGURE 1. Hot Gravity Filtration Setup FIGURE 2. Fluted Filter paper The colorless filtrate was then cooled down to room temperature, placed in an ice bath, and was stirred perpetually until crystallization was complete.This took about ton to fifteen minutes. When the crystallization was complete, the solution was vacuum filtered and then the crystals were washed in 2 mL of cold water. The crystals were then dried and weighed. The percentage recovery was then computed for and the melting point of the better crystals was determined using the Thomas Hoover Melting Apparatus. FIGURE 3. Vacuum Filtration Setup RESULTS Table I. Choice of Solvent (S=Soluble , I=In disintegrable) escalate Water Ethanol Benzene Ethyl Acetate Cold Hot Cold Hot Cold Ho t Cold Hot acetamide S S S S I S S S Acetanilide I S S S I S S SAspirin I S S S I S S S benzoic venomous I S S S S S S S Naphthalene I S I S S S S S Sucrose S S I S I I S S Compound Solvent trance for Recrystallization Acetamide Benzene Acetanilide Water Aspirin Benzene Benzoic Acid Water Naphthalene Water Sucrose Ethanol Table 1. 1 Table 1. 2 Table 2. Recrystallization of Impure Acetanilide Weight of crude acetanilide in grams 3. 53 g Weight of the filter paper in grams 1. 23 g Weight of the pure acetanilide in grams 0. 79 g Volume of water used in mL 62 mL Melting Point of pure acetanilide in 130-190 Percentage Recovery 29. 63 % Step Observation Boiling of crude acetanilide It boiled slowly and the boiling started at 90 C. ashen substance boiled as water was added black substance remained attachment of activated carbon Impurities in water were absorbed. Hot Gravity Filtration sinister substance was go forth on the filter paper and the white liquid went down and was expos ed from the black substance. Cooling in an ice bath Dissolved acetanilide formed white crystals. Vacuum Filtration The acetanilide was filtrated and what was left on the filter was the crystals. DISCUSSION In the experiment, all six of the sevensome criteria were vividly exhibited. The fist criterion states that the solvent should dissolve all of the compounds at high temperature. The second criterion is that the solvent should dissolve very little, or none of the compound at low temperatures. The third criterion is that the solvent should have different solubility with the impurities and the compound. The fourth and fifth criterion states that the solvent should have a low boiling point and that it should be lower than the melting point of the compound.The last criterion acquired from the experiment is that the solvent should be inert. In the first part of the experiment, we determined the most appropriate solvent for recrystallization of the compounds by checking whether the co mpound is insoluble in a cold solvent, and soluble when dipped in hot water bath. The results in Table 1. 2 are based on the data of Tables 1. 1, we chose such solvents because the compounds did not dissolve in the solvent at a low temperature, and it did at high temperature.Using an appropriate solvent for recrystallization is necessary because it can save you time, money and early(a) materials. Time because you are already sure that the solvent would be effective to use in dissolving the compound at certain temperatures, you wouldnt need to experiment anymore. For the second part of the experiment, the recrystallization of impure acetanilide, we were conducted to separate the impurities of the acetanilide by using the recrystallization process and by using water as the agent or the solvent for recrystallization.During recrystallization, minimum amount of solvent is used to dissolve the solute. This is important because if the amount of solvent exceeded the volume needed to disso lve the solute, recrystallization would not be possible anymore. A fluted filter paper was used in the hot filtration set up because it has a larger aerofoil area to catch the solid impurities, making it easier and more effective to separate the residues from the filtrate in the process.A stemless funnel was used during the hot filtration set up because unlike a regular funnel, the stem where the filtrate would limiting could recrystallize the solid immediately within its stem. If the funnel were stemless the filtrate would go straight down to the flask without crystalizing and compounds. The solution was not placed in an ice cold bath immediately after the hot filtration because the flask might have broke due to a drop in temperature. Vacuum filtration is used during the cold filtration step because it is asier to filter out the crystalized solid from the liquid since cold temperatures would already recrystallize the solid compounds. The cold crystals are washed with water to re move any impurities that are in the crystals. The main function of the activated carbon was to absorb any impurities in the water without reacting with it. Cooling the filtrate on an ice bath makes the recrystallization process accelerated because of the relatively low temperature. Based on the results on table 2, the percentage recovery was 29. 3%, which seems fairly low since 70. 37% of the crude acetanilide is impurities. Human error might have caused it to be that low and peradventure some crystals might have been left in the apparatus such as flasks. CONCLUSIONS AND RECOMMENDATIONS This experiment proves that the characteristics of choosing an ideal solvent for recrystallization are reliable and important. In the first part of the experiment, which had an objective of identifying the appropriate solvent for the recrystallization technique was achieved.The second objective, which was to use the recrystallization technique in purifying a solid sample, was also achieved. I would like to recommend that future researchers experiment on opposite solutes and solvents, preferably common ones in order to determine which solvents are most appropriate for recrystallization. An understanding of these compounds can be better obtained. REFERENCES 1. Baluyut, J. Y. G. , and De Castro, K. A. , Organic Chemistry Laboratory Manual For Chemistry Students Part1. 2. Klein, D. , (2011) Organic Chemistry, 1st Ed. , Cold joined States of America