Performed November 8th & 10th
Organic Chemistry 344
Objective: The purpose of this experiment was to synthesize adipic acid from cyclohexanol via an oxidation reaction that was catalyzed by sulfuric acid. Purity of the product was assessed by measuring the melting point.
Name| Formula| Molecular Weight (g/mol)| Boiling Point (0C)| Melting Point(0C)| Density(g/mL)| Hazards| Sodium Dichromate Dihydrate| Na2Cr2O7 . 2H2O| 297.98| 400.0| 357.0| 2.35| -Eye/skin irritant-Affects Respiratory System| Water| H2O| 18.02| 100.0| 0.0| 1.00| N/A|
Sulfuric Acid (98%)| H2SO4| 98.08| 337.0| 10.0| 1.84| -Eye/skin irritant-Affects Respiratory System-Produces large amounts of heat-Corrosive| Cyclohexanol| C6H12O| 100.16| 160.84| 25.93| 0.96| -Eye/skin irritant-Affects Respiratory System-Ingestion Hazard-May be combustible at high temperatures| Chromic Acid| H2CrO4| 118.01| 250.0| 197.0| 1.20| -Eye/skin irritant-Affects Respiratory System-Corrosive| Adipic Acid| C6H10O4| 146.14| 337.5| 152.1| 1.36| -Eye/skin irritant-Affects Respiratory System-May be combustible at high temperatures| Chromium (III) Salts| CrCl3| 266.48| 1300.0| 83.0| 1.76| -Eye/skin irritant-Affects Respiratory System| Alumina| Al2O3| 101.96| 2977.0| 2072.0| 3.95| -Eye/skin irritant-Affects Respiratory System| Source: Material Safety Data Sheet (2008).
Part I: Sodium dichromate dehydrate (14.99g) was placed in a 100 mL beaker and dissolved in 30.0 mL of water where it was observed to turn a neon orange color. The solution was cooled in an ice-water bath and 8.0 mL of sulfuric acid was slowly added to it in 1.0 mL portions. The chromic acid solution was then mixed until homogeneous and cooled to 10.00C in an ice-water bath. While the solution was cooling, 9.0 mL of sulfuric acid was carefully added to 25.0 mL of ice-cold water in a 125 mL Erlenmeyer flask and cooled to 200C. After the water-sulfuric acid mixture was cooled, 4.0 mL of cyclohexanol was added to the flask and swirled to mix all of the reagents. The chromic acid solution (5.0 mL) was added into the cyclohexanol-water-sulfuric acid mixture and swirled, at which point the mixture was observed to turn brown in color. The remaining chromic acid solution was then added to the reaction mixture in portions of 3.0 mL over a period of fifteen minutes, during which time the mixture’s temperature increased from 40.00C to 65.00C. After all of the chromic acid solution had been added, the reaction was left to stand for thirty minutes, swirling occasionally and making sure the temperature was kept between 55.00C to 65.00C. After the thirty minute standing period, it was observed that a green precipitate had formed. The mixture was then cooled to 10.00C in an ice-water bath, washed using three 20.0 mL portions of cold water, and filtered using vacuum filtration; leaving the crystals pale green and sugar-like in nature. The crude melting point and product yield was determined and the sample was stored for later experimentation.
Part II: The crude adipic crystals (2.01g) were recrystallized by dissolving them in distilled water (22.0 mL), heating the mixture until boiling, and then cooling it in an ice-water bath. The pure crystals where then dried for fifteen minutes using vacuum filtration, at which point they were observed to be white in color and granular. Finally, the pure product’s melting point and yield was determined and percent yield was calculated.
Data & Results:
Table 1: Adipic Acid Compound Data
Theoretical Yield of Adipic Acid| 5.60g|
Actual Yield of Crude Adipic Acid| 2.01g|
Actual Yield of Pure Adipic Acid| 1.98g|
Percent Yield of Pure Adipic Acid| 35.0%|
Limiting Reagent| Cyclohexanol|
Theoretical Melting Point of Adipic Acid|...