CHEM 3112 Beyond Labz Experiment 2: Nitration of Benzaldehyde Electrophilic aromatic substitution reactions are a class of reactions that are commonly employed to directly functionalize aromatic compounds. The reaction of the arene and the electrophile is the rate determining step which is followed by deprotonation and aromatization. In this experiment you will be performing a nitration of benzaldehyde. Nitric acid, when heated, is a good oxidizing agent which can form a nitronium ion without the addition of sulfuric acid. However, the rate of nitration is increased in the presence of sulfuric acid due to the increased concentration of the nitronium ion, the electrophile. Aldehydes are deactivating groups, and therefore meta directors in electrophilic aromatic substitution reactions. As a result, this experiment only has one possible product. In contrast, an activating group, such as an alkyl group, directs addition to both the ortho and para positions, forming two products. Nitration reactions are typically performed in a mixture of concentrated nitric and sulfuric acids at low temperatures, as the reaction is highly exothermic. Controlling the temperature is important for safety and to prevent the addition of multiple nitro groups to sufficiently activated rings. The product of this reaction however, 3-nitro-benzaldehyde, is strongly deactivated, and therefore the addition of a second NO2 group is extremely slow, with a massive energy barrier, and thus very unlikely. Therefore, this particular nitration reaction can be ran with heat, because otherwise the rate is very slow. Note that in the program, the nitric acid and sulfuric acid are already mixed, so it is not necessary to add both to your flask. Directions: 1. 2. 3. 4. 5. Open Beyond Labz Client. Choose the “Worksheets” tab. Choose “Organic Chemistry”. Choose “Aromatic Substitution”. Choose “Benzene Nitration – 1”; this should bring up a PDF file with the experimental procedure. 6. Back in the Beyond Labz Client, choose the “Labs” tab, and open “Organic Chemistry” 7. Under “Organic Worksheets” choose “Aromatic Substitution” then “VCL 8-1: Benzene Nitration – 1”. This should bring you to the lab bench. 8. You are now ready to attempt the experiment. Lab Report Questions: 1. List the starting materials, solvent, reagent, temperature range (low, room temp, or high) and products formed: 2. How long did it take to finish the reaction? 3. List any important IR peaks (If no noteworthy peaks, answer “none”). 4. Are there any IR peaks NOT PRESENT that indicate the product was formed? (Hint: think about the functional groups of the starting material and the product) 5. List the 1H NMR peaks. List the peak number, chemical shift, multiplicity (splitting pattern), and the integration. 6. List the 13C NMR peaks. List the peak number and the chemical shift. 7. What is the electrophile in this reaction? 8. What is the nucleophile in this reaction? 9. What is the catalyst (catalysts do not directly participate in the reaction, but increase the rate)? T.UU 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 200 175 150 125 100 75 50 25 FTIR Common Name: IUPAC Name: 2,2 2,3 2,4 2,5 2,6 2,7 2,82.03 BP: MP: MICRONS 3.5 45 6.5 100 10 11 12 13 14 15 16 17 18 19 21 23 25 LIFO.O 90 4.05 % 80 +0.1 tu -0.28 R 70 N 60 s M 50 0 0.3 B 40 0.4N N 30 -0.5 F0.6 Fo.7 E 20 10 IN F1.0 0 4500 4400 4200 4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1200 1000 800 600 2.0 400 1800 1600 1400 WAVENUMBERS
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