CHM 206 Expt 12

docx

School

University of Miami *

*We aren’t endorsed by this school

Course

206

Subject

Chemistry

Date

Feb 20, 2024

Type

docx

Pages

Uploaded by DrStrawKoala18

Experiment 12: Nitration of Methyl Benzoate – A Macroscale Synthesis Objective The purpose of this experiment is to apply electrophilic aromatic substitution reactions and macroscale synthetic procedures to understand the activation and deactivation of substituents. Table of Reagents Reagent Molar Mass ( g mol ) Melting Point (°C) Safety Sulfuric Acid 98.079 10.31 Causes severe skin burns and eye damage. Very strong acid and corrosive. Nitric Acid 63.01 -43.6 Very strong acid and corrosive. May intensify fire, oxidizer. Causes severe skin burns and eye damage. Wash any spills thoroughly. Methyl Benzoate 136.15 -15 Harmful if swallowed. Keep away from heat and flames. Methyl m-benzoate 181.15 78 Can cause eye and skin damage. Reaction Equations/Experiment Equipment and Apparatus

General Safety Any spills on clothes or skin should be reported to the TA right away in order to start the clean up process. If anything spills on you or your clothes go directly under the shower and rinse for 15 minutes and then follow up with NaHCO 3 . Procedure

1. Place 12 mL of concentrated sulfuric acid in a 100 mL beaker and cool to about 0 °C using an ice-water bath. 2. Add about 6 mg of methyl benzoate using a graduated cylinder and cool again to 0 °C. 3. Slowly add a cooled (0 °C) mixture of 4 mL of nitric acid and 4 mL of sulfuric acid using a Pasteur pipet. 4. Stir continuously with a glass rod and keep the temperature below 15 °C (ice bath). 5. Allow the mixture to warm to room temperature and wait 15 minutes. 6. Pour the reaction mixture onto ~50 g of ice in a larger beaker. 7. Stir and filter the mixture once all the ice has melted. 8. Wash the solids on the filter twice with 15 mL of cold water, then twice with 10 mL of cold methanol. 9. Weigh the crude product and recrystallize from methanol. 10. Filter and dry the crystals on top of the Buchner funnel. 11. Determine the melting point (~78 °C) and record the IR Spectrum using the ATR source. Observations  The temperature rose very quickly when adding methyl benzoate to the sulfuric acid. There was also vapor present.  The temperature would also rise quickly when adding the nitric acid and sulfuric acid mixture. o The color of the solution also turned yellow.  There was foaming present when adding the solution to the beaker with ice.  The two different crystals that came out as product were fluffy, white powders. Data and Results Volume of Methyl Benzoate (to use): 6 g ∗ 1 mL 1.084 g = 5.54 mL Crude Weight: 5.832 g Final Weight: 5.041 g Theoretical Yield of Methyl m -Nitrobenzoate: 6 g Methyl Benzoate ∗ 1 mol Methyl Benzoate 136.15 g Methyl Benzoate ∗ 1 mol Methyl m − Nitrobenzoate 1 mol Methyl Benzoate ∗ 181.15 g Methylm − Nitrobenzoat 1 mole Methyl m − Nitrobenzoate Percent Yield: 5.832 7.983 ∗ 100 = 73.05%

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Recovery Yield: 4.741 5.832 ∗ 100 = 81.92% Melting Point: 74.8-76.7 °C IR Spectra of Methyl m-Nitrobenzoate: Discussion and Conclusion The experiment turned out very well as our percent yield was 73.05%. Difficulty managing the reaction temperature could account for our lower percent yield. Moving the products between beakers and funnels also could have affected the percent yield. The crystals also could not have been fully dry after using the Buchner funnel. The combination of these problems could have lowered the percent yield and created some by products. In the IR Spectra of our product there were peaks at 1717.69 cm -1 (Carbonyl group) as well as 1527.26 and 1350.89 cm -1 (Nitro group). Looking at the IR from our collected product it can be seen that the product was relatively pure. The melting point recorded for the product was

74.8-76.7 °C. compared to the actual value which is 78 °C. This could have been due to the crystals not being fully dry lowering the melting point. Post Lab Questions 1. 2. Sulfuric acid is a very strong acid that can deprotonate itself, therefore, it dissolves in concentrated sulfuric acid, and then can protonate the carboxyl group in the methyl benzoate. 3. If the reaction was not maintained at 15 °C then ortho-, para-nitrobenzoate could have been formed.

4. Since it is lower in energy, therefore, more stable, it will favor the meta-position. 5. % Yield: 5.832 7.983 ∗ 100 = 73.05% Recovery Yield: 4.741 5.832 ∗ 100 = 81.92% 6. The IR was similar to the IR in the handbook since there were peaks at 1717.69 cm -1 and 2950 cm -1 . 7. Cold methanol removes water from the crystals and cleans the product. The cold temperature lets the crystals be less soluble allowing no products to be lost when washing. 8. Too much methanol would lead to product loss and a diminished yield. 9. HSO 4 -1 10. D 11. C 12. A

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version