- Experiment 8 Multistep Synthesis In Chemistry It Is Often Necessary To Run Multiple Reactions To Accomplish A Desired 1 (111.62 KiB) Viewed 33 times
Experiment 8: Multistep Synthesis In chemistry, it is often necessary to run multiple reactions to accomplish a desired transformation. In this experiment, you will be completing a multistep synthesis. Of particular note for the experiment is the reaction of o-vanillin with p-toluidine, which is accomplished without a solvent. Though these two reactants are both solids, the reaction actually occurs in the liquid phase, as mixing these two solvents causes them to melt due to their low melting points. For this reason (and others), this experiment is also a good introduction to Green Chemistry, which attempts to minimize the creation and use of environmentally damaging substances and processes. Imine Formation H + co-pro N 0-vanillin p-toluidine OCH3 Reduction of Imine H
Reduction of Imine H H NaBH4 EtOH H 0 OCH3 د کلي علل کم Acetylation OCH3 OCH
Pre-Lab Preparation Readings from Mohrig Green chemistry (22-32), Green chemistry (from Wikipedia), Convergent synthesis (from Wikipedia), Divergent synthesis (from Wikipedia) Physical Data Table Ortho-vanillin, para-toluidine, 95% ethanol, sodium borohydride, glacial acetic acid, acetic anhydride, hexane Prelab Calculations 2.5 mmol of ortho vanillin in grams 2.5 mmol of para-toluidine in grams 1.3 mmol of sodium borohydride in grams Procedure Imine Formation 1. Weigh 2.5 mmol of ortho-vanillin and 2.5 mmol of para-toluidine into a tared 20 ml beaker. NOTE: make sure to weigh equivalent molar amounts of both reactants. 2. Mix reactants with a glass rod. Continue until solids become a homogeneous dry powder. 3. Weigh the beaker to determine percent yield. Determine the IR and melting point of the
1. Weigh 2.5 mmol of ortho-vanillin and 2.5 mmol of para-toluidine into a tared 20 ml beaker. NOTE: make sure to weigh equivalent molar amounts of both reactants. 2. Mix reactants with a glass rod. Continue until solids become a homogeneous dry powder. 3. Weigh the beaker to determine percent yield. Determine the IR and melting point of the sample. NOTE: If product does not become a powder, recrystallize from hexanes and isolate before proceeding to the next reaction. Imine Reduction 4. Dissolve the imine product in 8 mLs of 95% ethanol. 5. Slowly add 1.3 mmol of sodium borohydride to the solution while stirring. Acetylation of the Imine 6. Add 1 mL of glacial acetic acid to neutralize excess borohydride and phenoxide. 7. Add 1 ml of acetic anhydride and gently heat the solution for 10 minutes. 8. Transfer the solution to a larger beaker and slowly add 40 mLs of deionized water while stirring with a glass rod. 9. Cool the mixture in an ice bath and collect the solid using vacuum filtration.
10. Once dry, weigh the product and determine its melting point. 11. Recrystallize the product from a minimal amount of hexanes. 12. Weigh the sample to determine percent yield. Determine the IR and melting point of the sample. Post-Lab Analysis 1. Why is it important to minimize the number of reactions in a synthetic pathway? 2. Which of the twelve principles of green chemistry are represented in this reaction? List specific examples. 3. Was this reaction an example of a convergent or divergent synthesis? Explain your reasoning. 4. Draw the mechanism for the reduction of the imine.