Cyclohexene

Oxidation of Cyclohexene to Adipic Acid Mitchell, Jerome Lab Partner: Atri, Jyotsna CHM0206-Organic Chemistry II – Section 10157 Dr. Saphronia R. Wallace August 8, 2011 Abstract The purpose of this experiment was to perform an oxidation reaction. The oxidation reaction used was the synthesis of adipic acid from cyclohexene. The percent yield of 53.12% adipic acid, suggests that several factors may have affected the outcome not to yield at 100% adipic acid. Even though the percent yield was low, the melting point test of the sample was 154-158°C, which was close to the literature value of 152.1°C. Adipic acid is used to manufacture nylon and polyurethane foams. Nylon and polyurethane are used in the make-up of medical equipment, parachutes, machine screws, clothing used from thermal insulation to sound proofing of rooms.4 Introduction Adipic acid is a white crystalline solid used primarily in the manufacture of nylon 6, 6 polymers for fibers and plastics. The largest global use of adipic acid (ADA) is in nylon 6, 6 production, which accounts for 73% of global output.  Nylon fiber accounts for 47% of the global market and nylon resin 26%. The non-nylon sector accounts for 27% of world demand, of which polyurethane (PU) is the largest. Smaller uses are in plasticizers, resins, coatings and polyamide 4,6.5 In this experiment, adipic acid was synthesized in one step starting from cyclohexene by way of oxidation. 3 Cyclohexene + 8 KMnO4 + 4 H2O yields 3 Adipic Acid + 8 KOH + 8 MnO2 as the complete balanced equation for the experiment. Oxidative cleavage is a known process in which the bonds of carbon atoms are broken. During the experiment, cyclohexene was oxidized by using potassium permanganate. The oxygen atoms in the KMnO4 are added to the carbon – carbon double bonds and dicarboxylic acid was formed. The heated reaction mixture coagulated the manganese dioxide that was removed through filtration over a vacuum. As a qualitative analysis of the sample, the melting point was taken and infrared spectroscopy was attempted to characterize the product. Data Figure 1: Oxidation of Cyclohexene to Adipic Acid2 Figure 2: Interpretation of the IR of Hexanedioic Acid (Adipic Acid)6 Table 1: Physical Data for All Chemicals Chemical | MW(g/mol) | mp(˚C) | bp(˚C) | density(g/mL) | Solubility | Hazards | | | | | | | | Cyclohexene | 82.15 | -103.7 | 82.8 | 0.8098 | Water | Flammable, Irritant | | | | | | | | Potassium | 158.03 | 240.0 | N/A | 2.703 | Partial in | Irritant | Permanganate | | | | Water | | | | | | | | | Sodium | 104.07 | 150.0 | N/A | 1.48 | Water | Irritant | Bisulfite | | | | | | | | | | | | | | Acetone | 58.08 | 94.5 | 56.5 | 0.7925 | Water | Flammable | | | | | | | | Hydrochloric | 36.47 | -25.0 | 109.0 | 1.19 | Water | Toxic, Corrosive | Acid | | | | | | | | | | | | | | Adipic | 146.14 | 152.15 | 337.5 | 1.36 | Water | Irritant | Acid | | | | | | | Calculations Amount of Cyclohexene used = mL Cyclohexene X Cyclohexene density 4.97 mL (0.8098 g/mL) = 4.0247 g Cyclohexene Mole Cyclohexene = g Cyclohexene / MW Cyclohexene Mole Cyclohexene = 4.0247 g / (82.15 g/mol) = 0.0490 mol Cyclohexene Amount of KMnO4 used = (mL KMnO4) X (M KMnO4) X (MW KMnO4) 0.250 L KMnO4 X (0.3 mol KMnO4/L) X 158.03 g/mol = 11.8523 g KMnO4 Mole KMnO4 = g KMnO4 / MW KMnO4 Mole KMnO4 = 11.8523 g / (158.03 g/mol) = 0.075 mol KMnO4 Cyclohexene is Limiting Reagent (LR) Cyclohexene and Adipic Acid 1:1 molar ratio 0.049 mol Cyclohexene X (3 mol Adipic Acid / 3 mol Cyclohexene) = 0.049 mol Adipic Acid Theoretical Yield = LR X MW Adipic Acid 0.049 mol Cyclohexene X 146.14 g/mol Adipic Acid = 7.16 g Adipic Acid Scintillation vial empty = 15.0625 g Scintillation vial (+) Adipic Acid = 18.866 g Measured mass Adipic Acid = Actual = 3.8035 g Adipic Acid Percent Yield = (Actual / Theoretical) X 100 Percent Yield = (3.8035 g Adipic Acid / 7.16 g Adipic Acid) X 100 = 53.12 % Adipic Acid Melting point first observed = 154˚C Melting point after all adipic acid melted = 158˚C Results and Discussion The moles of cyclohexene were calculated to be 0.049 g and therefore making it the limiting reagent. The theoretical yield was calculated to be 7.16 g of adipic acid which was compared to the actual yield of 3.8035 g. The percent yield was calculated to be 53.12 % in which the pH, cooling down period, and the boiling of the solution may have affected the outcome. The solution appeared to not have been completely mixed after pouring it into the Buchner funnel, due to the precipitate left in the Erlenmyer flask.. Cold water was used in an attempt to rinse completely. During filtration, the brown precipitate was left on the filter paper and discarded as waste. The pH paper was used as drops of hydrochloric acid was added to the beaker, to monitor the pH of the solution, from a pH of ten to lower it to a pH two.. The accuracy was problematic due to the close color range of pH 2, 3, and 4 on pH paper. A pH meter would have made the monitoring of the acidity of the solution more accurate. During the point of boiling the solution, it was noticed at a low volume that some of the solution was boiling out of the beaker, which could affect the yield. The beaker was removed from the heat without knowing how close the volume was to 10 mL. The sample was dried over-night in a 60˚C oven where 3.8035 g of adipic acid was obtained from the filter paper. A small amount of the adipic acid sample was measured on a melting point apparatus and showed a melting point range from 154 - 158˚C. Due to the fact that the literature melting point value is 152.1˚C, there may have been some impurities that caused the temperature to be slightly higher than the literature value. A Fourier Transform Infrared Spectroscopy (IR) was the final step in the experiment to analyze the product. Unfortunately, the adipic acid would not dissolve in ethanol, methanol, chloroform, or acetone. Therefore, the ability to run aproper IR spec was not an option. If an IR spec was ran, the graph would be expected to look like Figure 2 in the data section. On figure 2, the absorption at 3000 cm-1 can be considered the O-H bond of the carboxylic acid and the absorption between 1670 – 1780 cm-1 can be considered the C=O. Everything below absorption 1500 cm-1 can be considered fingerprint portion because of various C-C, C-O, C-N, and C-X that occur.3 Conclusion Experimental Section The experiment was conducted with laboratory safety, which was utilized throughout the entire lab. Safety glasses, gloves, and buttoned lab coats were used during the operation of the experiment. An Erlenmeyer flask was used to prepare 0.3 M solution of potassium permanganate. The amount of potassium permanganate was calculated and it was found that 11.85 grams needed to be added to the flask as the volume was brought up to 250 mL with distilled water. Another Erlenmeyer flask was used to add 4.97 mL of cyclohexene to 50 mL of acetone. The permanganate solution was added to the cyclohexene/acetone flask using approximately 25 mL every two minutes while swirling the flask. The solution was heated between 55-60˚C in a sand bath for 30 minutes. The darkened solution was removed from the heat and 10.0884 grams of sodium bisulfite was added to the solution. The solution was chilled on ice and the Buchner funnel apparatus was erected with the vacuum pump and sidearm flask. Filter paper was placed in the Buchner funnel and placed on top of the side arm flask. After the solution was poured out of the Erlenmeyer flask, it was rinsed with cold water and it was poured back into the Buchner funnel apparatus to remove the sample. The precipitate on the filter was removed as waste while the clear filtrate was placed into a 600 mL beaker. Drops of hydrochloric acid were used to bring the pH of the solution to 2. The acidity was checked with pH paper. The solution was placed under the hood and boiled until the volume was reduced to approximately 10 mL. The remaining solution was chilled in an ice bath until filtration. Another filter was placed in the Buchner funnel as the solution was air dried by the vacuum. The filter was removed with the adipic acid crystals and placed on a watch glass. The watch glass was placed in a 60˚C oven until filter was completely dry. The precipitate was then placed in a pre-weighed scintillation vial for storage. A very small amount was placed on melting point machine and observed melting point to be between 154-158˚C. A Fourier Transform-Infrared Spectroscopy was attempted for characterization, but was inconclusive through technical difficulties in the lab.1 References 1Gwinnett Technical College, Lab Worksheet # 3: Oxidation of Cyclohexene to Adipic Acid, Dr. Saphronia R. Wallace. 2Jerome Mitchell. Oxidation of Cyclohexene to Adipic Acid 2011, Laboratory Notebook, pp 11-15. 3McMurry, J. Organic Chemistry, 7th ed.; Thomson: Belmont, Ca, 2008: 425-429. 4 China Chemical Reporter; 6/6/2011, Vol. 22 Issue 11, p19-20. 5 ICIS Chemical Business; 2/28/2011, Vol. 279 Issue 8, p43. 6Smith, A.L., The Coblentz Society Desk Book of Infrared Spectra in Carver, C.D., editor, The Coblentz Society Desk Book of Infrared Spectra, Second Edition, The Coblentz Society:Kirkwood, MO, 1982, pp 1-24.