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Brown Brittney Title: Multi-step synthesis of 4-bromo-2chloroacetanilide Lab Partner: Chelsea Searels Due: 10-29-2009 The purpose of this lab was to covert 4-bromo-2-chloroacetanilide from aniline through a series of steps being attentive of the percent yield. Experimental infrared spectroscopes and melting points were obtained of the products for confirmation of the desired products. Experimental Details: Table 1. List of Reagents/Reactants Substance Amount Molecular Weight (g/mol) mmol Density (g/ mL) Boiling/ Melting Point (C) Week One: Preparation of Aniline from Nitrobenzene Granulated tin Nitrobenzene HCl Sodium hydroxide 6.096g 2.6mL 13mL 12mL 118.71 123.06 36.46 39.997 50.7 25.3 420 639 7.287 1.199 1.18 2.13 MP=232C BP= 210.9C BP= 110C MP= 323C Week Two: Acetanilide from Aniline and 4-bromoacetanilide from Acetanilide Recovered aniline Stock aniline HCl Sodium acetate Acetic anhydride Ethanol Bromine 0.3g 2.0mL 2.1mL 2.484g 2.8mL 3.3mL 1mL 34.46 82.02 102.09 46.07 70 67.96 30.29 24.87 90.8 44.33 1.18 1.528 1.089 0.789 3.1028 BP=110C MP= 324C BP=39.8C BP=78.4C BP= 58.78C 1 93.13 25.23 1.0217 BP=184.83C Week Three: 4-bromo-2-chloroacetanilide from 4-bromoacetanilide Suspeneded 4bromoacetanilide HCl Acetic acid NaClO3 2.00g 6mL 7mL 0.501g 214.06 36.46 60.05 106.5 9.3 139 111.12 4.6 1.717 1.18 1.049 2.5 166-170C BP= 110C 118.1C MP= 448C The mutli-step synthesis was completed over a course of three weeks. In the first week, aniline was prepared from nitrobenzene by adding 6.094g of granulated tin combined with 2.6mL of nitrobenzene in a 100-mL boiling flask. An ice bath made at 0C and 13mL of HCl was added to the solution. A thermometer was inserted and the solution was stirred, maintaining a temperature of between 55 and 60C. After 15 minutes, the mixture was heated on a reflux to ensure the completion of the reaction. Only 0.3g of aniline was collected. The aniline was noted as orange oil droplets suspended in the solution. For the second week, the synthesis continued in preparing acetanilide from aniline and 4-bromoacetanilide from acetanilide. The recovered aniline was mixed with 2mL of stock aniline to perform the experiment. About 50mL of water and 2mL of HCl was added to the aniline. A solution of 2.8mL of sodium acetate and 15 mL of water was prepared. To the aniline hydrochloride solution, 2.8mL of acetic anhydride was added followed by the solution of sodium acetate. The mixture was swirled for about 5 minutes then cooled in an ice bath. The precipitate was filtered and weighed. Next, 2.5g of the recovered product was added to 10mL of glacial acetic acid and stirred. Then, a solution of 1.04mL of bromine and 2mL of glacial acetic acid added. The mixture was stirred for 5 minutes while slowly adding 80mL of water. Enough sodium bisulfate was added to discharge the yellow color. The product was recrystallized by adding ethanol. The product was filtered and rinsed with water. Finally in the last week, 4-bromo-2-chloroacetanilide was prepared from 4bromoacetanilide by weighing out 2.00g of 4-bromoacetanilide to suspend in 6mL of HCl and 7mL of acetic acid. The solution was heated on a hot plate until the solid was completely dissolved then cooled in an ice bath (0C). A solution of 0.500g of sodium chlorate and 1.5mL of water was added under the hood. The solution was allowed to stand for an hour. The solution was filter and the product collected and weighed (1). An IR was obtained for the products (4bromo-2-chloroacetanilide, 4-bromoacetanilide, and acetanilide). Data: Table 2. Data collected Mass of product (aniline) Mass of product: (Acetanilide) 2.905g 0.300g 2 (4-bromoacetanilide) Mass of product (4-bromo-2chloroacetanilide) Melting Points for product (acetanilide) Melting Points for product (4-bromoacetanilide) Point Melting for product (4-bromo-2-chloroacetanilide) Percent Yield (aniline) Percent Yield: (Acetanilide) (4-bromoacetanilide) Percent Yield (4-bromo-2chloroacetanilide) Overall Percent Yield 3.678g 1.309g 1) 113-116C 2) 114-118C 1) 164-167C 2) 165-171C 1) 148-150C 2) 149-153C 13% 73% 89.1% 56.4% 4.8% Percent yield for aniline: 0.300g2.360gx 100%=13% Percent yield for acetanilide: 2.905g4.000gx 100%=73% Percent yield for 4-bromoacetanilide: 3.678g4.130gx 100%=89.1% Percent yield for 4-bromo-2-chloroacetanilide: 1.309g2.320gx 100%=56.4% Overall Percent Yield: (0.13)(0.73)(0.891)(0.564) x 100% = 4.8% Table 3. IR peaks and their corresponding functional group for acetanilide Location of Peak (cm-1) 3290.73 1661.91 1559.37 N-H C=O C=C 3 Functional Group Table 4. IR peaks and their corresponding functional group for 4-bromoacetanilide Location of Peak (cm-1) 3298.85 3261.24 1667.67 1602.26 N-H N-H C=O C=C Functional Group Table 5. IR peaks and their corresponding functional group for 4-bromo-2-chloroacetanilide Location of Peak (cm-1) 3274.42 1664.22 1580.92 N-H C=O C=C Functional Group Discussion: For the first week, only 0.300g of aniline was collected from experiment. The orange oil droplets were suspended in the solution were concluded to be the aniline. In order to start the next experiment, 2.00mL of stock aniline was used. Errors such as not checking the pH of the solution before it was refluxed could have contributed to the low percent yield of 13%. Most likely there was not enough NaOH added in order for the solution to be basic enough for a high percent yield. There was a 73% yield for acetanilide to start the next experiment which was average. The percent yield obtained for 4-bromoacetanilide (89.1%) was above average. Each percent yield were important because it was dependent on the follow-up experiment (1). The melting points were obtained for acetanilide, 4-bromoacetanilide, and 4-bromo-2chloroacetanilide. The melting point ranged between 113 and 1118C for acetanilide, 164 and 171C for 4-bromoacetanilide, and 148 and 153C for 4-bromo-2-chloroacetanilide. In comparison to the literature values of 115C for acetanilide, 169C for 4-bromoacetanilide, and 151C for 4-bromo-2-chloroacenatilide, the actual melting points fit the range of the experimental melting points (3). The melting points were important in making predictions on the relative purity of each product. Infrared Spectrums were also obtained for acetanilide, 4-bromoacetanilide, and 4bromo-2-chloroacetanilide which were the products at the end of week. For acetanilide there were three defining peaks of a N-H at 3290.73 cm-1, a C=O at 1661.91 cm-1, and a C=C (arene) at 1602.26 cm-1. The peaks for 4-bromoacetanilide included two N-H at 3298.85 cm-1 and 4 3261.24 cm-1, a C=O at 1667.67 cm-1, and a C=C (arene) at 1602.26 cm-1. Lastly, the peaks for 4-bromo-2-chloroacetanilide included a N-H at 3274.42 cm-1, a C=O at 1664.22 cm-1, and an C=C (arene) at 1580.92 cm-1. All of the experimental peaks fit the range of the actual peaks of each of the products insisting of a N-H and C=O peak for the amide, and a C=C for the arene (2). The IR supported the data in confirming that the obtained products at the end of each experiment were indeed the desired products. Although the overall percent yield for the experiment was 4.8%, 1.309g (56.7%) was successfully converted through the multi-step synthesis. References: 1. Alexander, Christopher. Multi-step Synthesis. PowerPoint Kennesaw State University. Kennesaw, GA. October 24, 2009. Presentation. 2. Ault, A. Techniques and experiments for Organic Chemistry; University Science books: Sausalito, CA, 1998; pp. 454, 459-464, 615-617 3. (accessed October 27, 2009) 5 ... View Full Document

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