Recrystallization of Benzoic Acid

The objective of this experiment was to observe multi-step finish of benzoic venereal disease subsequently performing the extraction from a mixture containing benzoic mordant, cellulose, and methyl o draw. Re vitreous silicalization was by to remove impurities from the sample. The totality of BA recovered during recrystallization is much less than the extracted amount of BA. The difference amidst the light and im subtle samples was observed by semblance of warming calculates. It was found that im fresh samples leave alone exact a overthrow and wider liquescent gear up range.The experiment performed was important because it provides important knowledge almost the chemic nature and reactivitys of different obscures that female genitalia be employ in everyday life. Introduction Now that the desired compound is extracted, it still contains impurities. These impurities bunghole be removed through a attend called recrystallization. Recrystallization is a method f or correcting truehearted compounds which atomic number 18 frequently the proceedss of essential reactions. This theory is based on three important concepts. The step forwardgrowth is that a compound is always more soluble in hot declarations than in cold solvents.Secondly, molecules swallow unique solubility properties. Lastly, a growing crystal leave behind only accept similar entities into its latt frosting. This is related to the crystal lattice theory which states crystal governing body is anti-entropic based on the equation ? G =? H-T? S. There be three stages of solubility collision, dissociation, and solvation. In order to paint a picture the probability of collision between the solute and solvent, heat is cast uped to the governing body. When this occurs, the solute impart attack the pellucid structure of the solute and start dissociation. As dissociation continues until all the molecules are free, solvation occurs.Choosing the in effect(p) solvent is imp ortant when considering recrystallization. The solute mustiness consider a high temperature coefficient in the solvent it must be soluble at high temperatures and insoluble at low temperatures, satisfying the first principle stated above. to a fault the boiling point of the solvent must be put down than the liquescent point of the solute. This allow for ensure that the solute fragmentises in the solvent and does not melt. The solvent must also be inert to prevent chemical interactions with the solute. Impurities must either be readily dissolved in the solvent or be insoluble.The solvent must also be volatile, and finally, it would be practiced to the experimenter if the solvent is relatively inexpensive. Once the semblance and most impurities are removed, the crystals can be formed in the ascendent through a swear out called nucleation. Nucleation can be induced by slack uply cooling the resoluteness to dwell temperature. It is important to do this checkly so that ha nd close to solute resembling impurities do not enter the crystal lattice, as described by the terzetto principle of recrystallization. Chemists often cater already pure crystals of the solute to the resoluteness in order to provide a pre-formed lattice for other molecules to enter.This is called set outing. Scratching the folderol container in which the resolvent is contained with a methamphetamine hydrochloride stir rod lead also induce nucleation on microscopic glass particles. The concept of start is similar to that of seeding. Finally, nucleation can be induced by cooling the result farther in an ice bath however, this is only a farthermost resort hotel option over delinquent to its least efficiency to bring frontwards crystals. The crystallized solute can then be collected by clean filtration. There is a difference observed in the physical properties of the pure compound and the impure mixture. One of the tests of purity is liquescent point.Melting point is an intrinsic, or intensive, property the value is independent of the quantity of the substance. Melting point is the temperature at which a substance changes physical state from solid to perspicuous. Because the substance will develop a certain shape and surface area exposure, thither will be a time interval in which the melting occurs. Thus, it is more accurate to refer to this as melting range. Melting range encompasses the temperature at which the first particles can be seen turning from solid to liquid until all the sample is in the liquid state. Purer samples have smaller melting ranges.Perfectly pure compounds will have ranges of only 1-2C. Impurities lower melting point below literature values and also widen the range between which melting occurs. New techniques and equipment used were used during both parts of the purification process. Activated fusain was used to adsorb impure color in products. sedateness filtration was used to remove insoluble products which were im purities. Fluted filter paper was used to shoe collar more of the impurities. A heating mantel was introduced during recrystallization. It is a heat first used for solutions. For determining the melting point of benzoic vinegarish, a Mel-Temp instrument was use.It is used for determining when a small amount of a solid begins to melt and when the melting ends while studying the temperatures, respectively. Experimental Recrystallization Lab Initially, took a small amount of impure BA to the side for following workweeks lab. The impure BA crystals were weighed, using an analytical balance, and then primed(p) in a 250 mL Erlenmeyer flaskful. 200 mL of pee was turn (with boiling stones) in a 250 mL round bottom flask using a heating mantel. The boiled wet was added behind to the benzoic erosive crystals. Only enough water was added to dissolve the BA crystals.For the pl causticity of the lab the Erlenmeyer flask was kept on a steam bath. brown coal was added to the BA solu tion and then gravity filtered using a funnel shape with fluted filter paper. The filtrate was collected in a 250 mL Erlenmeyer flask. If color in the BA solution still remained then charcoal should be added again. The BA solution was removed from the steam bath and cooled, preferably on a window sill. If crystals did not form while cooling on window sill, use another method to induce nucleation to the start the formation of crystals. The crystals were collects by vacuum filtration and placed on a line up subsequently glass to dry.Melting evidence of benzoic paneling A melting point tobacco pipe was loaded with BA crystals by inverting the tube into the BA crystals on the watch glass. The tube was packed by dropping through a funnel. The Mel-Temp frame-up was used to define the melting point range. A rapid melting range experiment was done first and then a slow melting range experiment was carried out to get a give way range. Results Recrystallization lab Observations non much charcoal was used to adsorb the colored molecules The BA crystals were small, shiny, flaky, and white. Almost compar commensurate to texture of dandruff. Data Mass of extracted Benzoic Acid = 2. 3 g Mass of recrystallized Benzoic Acid = 1. 84 g Calculations portion (%) retrieval =(weight later on recrystalization)/(mass stark naked BA) ? 100 Percent (%) recovery =(1. 84 g)/(2. 43 g) ? 100=75. 72% Melting set lab Observations Once the benzoic stinging began to melt, it happened very quickly.It was hard was uncontrollable to watch the melting and recording the start and end temperature. The crude BA had a lower and wider melting point range. Data Melting Point Ranges RunCrude (Impure) Benzoic Acid (C)Purified Benzoic Acid (C) Fast 110. 2-118. 4 at 4. 5 selectivity (Range 8. 2)115. 4-118. 5 at 4 selectivity(Range 3. ) Slow113. 2-117. 3 selectivity (Range4. 1)117. 5-120. 0 selectivity (Range 2. 5) give-and-take The cultivation of recrystallization and determining melting p oint labs were to explore the techniques used to puzzle pure samples from desired compounds. aft(prenominal) the extraction the goal was to recrystallize the benzoic demigod and determine the per centum recovery. Then the goal was to determine the melting point range of the recrystallized benzoic acid and compare it to the melting range of the small sample of the impure benzoic acid. 1. 84 grams of pure benzoic acid was obtained, which was calculated to be 75. 2% from the 2. 43 grams of impure benzoic acid.The percent recovery from the impure sample shows that about three fourths of the sample was able to be collected as pure benzoic acid, and that 0. 59 g of the impure benzoic acid was impurities. From this the experimenter can infer that the pure benzoic acid accounted for most of the mass or that little benzoic acid was lost with the removal of the impurities. Also, there is always a chance that near of the benzoic acid may have remained in the solution rather of crystalli zing. Also, using an ice-bath to induce nucleation could have lowered my results or recrystallization because it was the last resort to crystalize the solute. Maybe adding too much charcoal could have adsorbed some of the solute. The charcoal was used to adsorb any of the cellulose (which is the reason for the color) that was left behind. Not too much charcoal was actually used however, my benzoic acid solution did not have much color so charcoal may not have been needed.Note that the initial value for percent recovery is slightly less than the extracted mass because of the impure benzoic acid set aside for the melting point comparison. The total composition from the very first starting benzoic acid mixture is only 44. 2% (1. 84 grams / 4. 17 grams). Considering practical purposes of recrystallization, one comes to realize how important it is to make this processes as efficient as come-at-able to save money and gain as much product as possible, for example with ibuprofen purificati on for the pharmaceutical industry. The purity of the sample is shown by the melting range. As expected, the pure benzoic acid had the smallest melting point range of 2. 5C. From this, one can tell that this sample was not perfectly pure because pure compounds have melting point ranges of less than 1C.There may have been some impurities left in the sample since activated charcoal was not used for this sample. Human error while scraping the impure mixture from the funnel and also from the Erlenmeyer flask would result in a decreased yield. Also, the nucleation may have had some impurity particles collect in the lattice when recrystallizing. After performing the rapid and slow experiment, the temperatures (especially for the pure BA) were not similar. This was probably due to what is called thermometer lag. If the Mel-Temp apparatus selectivity was higher than the temperature readings were not as accurate as the slow experiment.The actual value for the melting range coincides with th e literature value of 122. 4C given in the reagent table. The impure sample, however, had a significantly bigger melting range of 4. 1C. Also, the impure sample had a lower temperature. This is because impurities disrupt lattice forces and decrease the energy required to break the intermolecular bonds between benzoic acid molecules. One way that this experiment could have been improved is to have more space to perform the various move in the lab. A lot of the mistakes and errors committed (i. e. pillage) were due to crowding of various equipment that were closely packed next to each other. Overall, theses labs were a success be the experimenter was able to achieve the goals of each lab. The benzoic acid was able to recrystallize and the melting point was fairly close to the literature value even with possible errors performed in lab.Works Cited Wikipedia The Free Encyclopedia. Wikimedia Foundation, Inc. 22 July 2004. Thurs. 7 Oct. 2010. Zubrick, James. The Organic Chem Lab pick Ma nual. 6th. Pittsburgh John Wiley & Son, Inc. , 2008. Print.Recrystallization of Benzoic AcidRecrystallization of Benzoic Acid Objective To purify benzoic acid by recrystallization and gain experience with a basal organic laboratory techniques. stage setting Products of chemical reactions are often begrime with impurities. One method for make pure chemicals, recrystallization, takes benefit of the differences in the solubilities of the desired products and the impurities and the drift for the slow formation of crystals to pull out impurities from the crystalline solid. HC HC HC CH C CH MgBr + CO2 + HCl HC HC HC CH C CH CO2H ClMgBrBenzoic acid, the chemical that we will be purifying, can be do by reacting phenylmagnesium bromide with hundred dioxide. When the product of that reaction is treated with hydrochloric acid, benzoic acid is formed. From the balanced chemical equation, it is clear that the benzoic acid will not be pure since the byproduct MgClBr, an dome solid, form s at the aforesaid(prenominal) time the desired product forms. Benzoic acid can be separated from garret solids because the materials have different solubilities in water.At room temperature, benzoic acid is not particularly soluble in water, whereas ionic solids like MgClBr are. Thus, adding water to the crude reaction products will dissolve the ionic solid, and nearly all of the benzoic acid will remain undissolved. If the fault were filtered, much of the impurity would be washed away however, the resulting product wouldnt be as pure as a recrystallized product. To take advantage of the extra purity garnered by crystallization, all of the benzoic acid must be dissolved. On the other hand, the benzoic acid needs to come back out of solution to crystallize.Simply adding room-temperature water cannot accomplish this goal once the benzoic acid is dissolved there would be no reason for it crystallize. Since benzoic acid is much more soluble in hot water as compared to cold, small amo unts of hot water are added to dissolve the benzoic acid. If the hot, double-dyed(a), aqueous solution of benzoic acid is cooled, the solution becomes supersaturated, and the supersaturated solution crystallizes. map 1. Obtain a sample of copper(II) sulphate begrime benzoic acid. 2. ply approximately 0. g (record the actual mass) of the contaminated benzoic acid and 5 mL of water to a 25-mL Erlenmeyer flask. 3. warmly the flask and its contents on a hot graduated table and easily add near-boiling water to dissolve the solids. 4. Continue to warm the flask and add near-boiling water until all of the solids have disolved 5. Remove the flask from the hot plate and allow it to cool slowly on the bench top. Covering the flask with a beaker can military service slow the rate at which the solution cools. After approximately twenty dollar bill minutes, crystals will have formed.Cool the gap further using an ice bath. If crystals have not formed after 20 minutes, there are a few t echniques that can be used to coax the crystals out of solution. Often scratching the glass container with a glass rod will induce crystallization. Alternatively, a seed crystal can be obtained by evaporating a drop of the solution on the tip of a inspiration rod or spatula. Returning this seed crystal to the super saturated solution will cause crystals to form. 6. send the crystals to a Hirsch funnel, and filter the benzoic acidwater suspension. . Wash the benzoic acid crystals with ice-cold water by pouring ice-cold water over the crystals. 8. Dry the crystals on the Hirsch funnel that is, allow the vacuum filtration system to draw air through the crystals until the mass of the crystals remains relatively constant. describe the benzoic acid in your drawer and allow it to dry completely. 9. darn the benzoic acid is drying, gasify the water from the aqueous CuSO4 solution. Remember to add a magnetic stir bar to your flask to lower the find of spattering. 10.Note the appearance o f your CuSO4, and, if possible, record the mass of the CuSO4 that you obtained. 11. After allowing the benzoic acid crystals to dry for a week, determine the mass and the melting point of the benzoic acid. Experimental Report issue an experimental describing the procedure that you followed to recrystallize the benzoic acid. A first draft of the experimental is due one week after steps 110 have been completed. A final feign that includes the final mass and the melting point of the benzoic acid is due one week after step 11 is completed.Recrystallization of Benzoic AcidRecrystallization of Benzoic Acid Objective To purify benzoic acid by recrystallization and gain experience with a basic organic laboratory techniques. Background Products of chemical reactions are often contaminated with impurities. One method for purifying chemicals, recrystallization, takes advantage of the differences in the solubilities of the desired products and the impurities and the tendency for the slow for mation of crystals to exclude impurities from the crystalline solid. HC HC HC CH C CH MgBr + CO2 + HCl HC HC HC CH C CH CO2H ClMgBrBenzoic acid, the chemical that we will be purifying, can be made by reacting phenylmagnesium bromide with carbon dioxide. When the product of that reaction is treated with hydrochloric acid, benzoic acid is formed. From the balanced chemical equation, it is clear that the benzoic acid will not be pure since the byproduct MgClBr, an ionic solid, forms at the same time the desired product forms. Benzoic acid can be separated from ionic solids because the materials have different solubilities in water.At room temperature, benzoic acid is not particularly soluble in water, whereas ionic solids like MgClBr are. Thus, adding water to the crude reaction products will dissolve the ionic solid, and nearly all of the benzoic acid will remain undissolved. If the suspension were filtered, much of the impurity would be washed away however, the resulting product woul dnt be as pure as a recrystallized product. To take advantage of the extra purity garnered by crystallization, all of the benzoic acid must be dissolved. On the other hand, the benzoic acid needs to come back out of solution to crystallize.Simply adding room-temperature water cannot accomplish this goal once the benzoic acid is dissolved there would be no reason for it crystallize. Since benzoic acid is much more soluble in hot water as compared to cold, small amounts of hot water are added to dissolve the benzoic acid. If the hot, saturated, aqueous solution of benzoic acid is cooled, the solution becomes supersaturated, and the supersaturated solution crystallizes. Procedure 1. Obtain a sample of copper(II) sulfate contaminated benzoic acid. 2. Add approximately 0. g (record the actual mass) of the contaminated benzoic acid and 5 mL of water to a 25-mL Erlenmeyer flask. 3. Warm the flask and its contents on a hot plate and slowly add near-boiling water to dissolve the solids. 4. C ontinue to warm the flask and add near-boiling water until all of the solids have disolved 5. Remove the flask from the hot plate and allow it to cool slowly on the bench top. Covering the flask with a beaker can help slow the rate at which the solution cools. After approximately twenty minutes, crystals will have formed.Cool the suspension further using an ice bath. If crystals have not formed after 20 minutes, there are a few techniques that can be used to coax the crystals out of solution. Often scratching the glass container with a glass rod will induce crystallization. Alternatively, a seed crystal can be obtained by evaporating a drop of the solution on the tip of a stirring rod or spatula. Returning this seed crystal to the super saturated solution will cause crystals to form. 6. Transfer the crystals to a Hirsch funnel, and filter the benzoic acidwater suspension. . Wash the benzoic acid crystals with ice-cold water by pouring ice-cold water over the crystals. 8. Dry the cry stals on the Hirsch funnel that is, allow the vacuum filtration system to draw air through the crystals until the mass of the crystals remains relatively constant. Place the benzoic acid in your drawer and allow it to dry completely. 9. While the benzoic acid is drying, evaporate the water from the aqueous CuSO4 solution. Remember to add a magnetic stir bar to your flask to lower the risk of spattering. 10.Note the appearance of your CuSO4, and, if possible, record the mass of the CuSO4 that you obtained. 11. After allowing the benzoic acid crystals to dry for a week, determine the mass and the melting point of the benzoic acid. Experimental Report Write an experimental describing the procedure that you followed to recrystallize the benzoic acid. A first draft of the experimental is due one week after steps 110 have been completed. A final copy that includes the final mass and the melting point of the benzoic acid is due one week after step 11 is completed.