Prepare an ice bath in a 100-mL beaker on a magnetic stir plate. To a clean, dry
ID: 534170 • Letter: P
Question
Prepare an ice bath in a 100-mL beaker on a magnetic stir plate. To a clean, dry 5-mL conical vial, pipet 0.20 mL of methyl benzoate. To the methyl benzoate, add 0.45 mL of concentrated (18 M) sulfuric acid and a spin vane. Attach an air condenser to the conical vial. Carefully clamp the apparatus so that the vial is immersed in the ice bath. Begin stirring. Into a clean, dry 3-mL conical vial, add 0.15 mL of concentrated (18 M) sulfuric acid and 0.15 mL of concentrated (16 M) nitric acid. Cool the mixture in a second ice hath. With a Pasteur pipet, slowly add the cooled sulfuric acid-nitric acid solution to the stirred solution of methyl benzoate through the air condenser. The addition should take approximately 15 minutes. Adding the nitrating agent more rapidly increases the amount of by-products and decreases the yield. When all the nitrating agent has been added, carefully remove the ice bath. Continue stirring until the reaction has come to room temperature. Then let the reaction flask stand undisturbed for 15 minutes. Place 2 g of ice in a 30-mL beaker. With a Pasteur pipet, transfer the reaction mixture to the beaker. Rinse the reaction vial with 1 mL of cold water. When the ice has melted, vacuum filter the crude crystals using a Hirsch funnel. Wash the crystals with two 1.0-mL portions of cold water and finally with two 0.3-mL portions of cold methanol. The crude product can be recrystallized from methanol. Record the mass of the dry product and calculate the yield.Explanation / Answer
The reaction mentioned above is the nitration of methyl benzoate where the nitration happens only at the meta position but no at the ortho and para positions. This is due to the effect of ester substituent attached to the benzene ring. The carbonyl group is electron withdrawing group hence deactivates the orho and para groups by decreasing the electron density in them but the meta position will be having hhigher electron density compared to ortho and para positions due to resonance. Hence the incoming nitro group attacks meta position giving meta nitro methyl benzoate.