a. Below is the reaction to synthesize DEET, the insect repellant using an amide
ID: 474685 • Letter: A
Question
a. Below is the reaction to synthesize DEET, the insect repellant using an amide bond coupling agent, DCC. Excess diethyl amine base (2) is utilized in this synthesis. Answer the following SIX questions regarding this reaction.
1. Knowing that excess 2 is used in this reaction, how would you QUENCH this reaction? Would you use acid or base? Explain.
2. If 1.0 g of DEET were synthesized in this reaction, what is the most appropriate glassware for this type of workup? Why?
3. After the quench, the product must be isolated from the reaction mixture. Suppose dichloromethane is added to the quenched reaction mixture. What layer is on the top and what layer is on the bottom (organic or aqueous)? Why?
4. Using your knowledge of acid/base chemistry, what species will be initially present in the organic layer after the quench?
5. What species will be present in the aqueous layer after the quench?
6. If leftover starting material 1 is present, can it be removed via acid/base extraction in the workup? Explain.
O O OH DCC N CH2Cl2 CH3 CH3 2 -C D-H NHExplanation / Answer
Answer:
1) The reaction can be quenched with the Ice. Then its PH is neutralized with 1N aqueous HCl solution. Then the aqueous layer is extracted with the DCM to get the compound.
2) For the 1 g preparation 50 mL of the Round bottom flask with two neck, one stopper or rubber septa and the stop key to create the Innert atmosphere in the reaction.
For the work up: one separating funnel (100 mL) and two conical flasks required. One for the DCM layer and one for Aqueous layer.
3) After quenching with water and adding the DCM, The reaction mixture is poured in the separating funnel.
The dencity of DCM is more than the water. Hence it becomes as bottom layer in the separating funnel.
4) The compound DEET goes in to the DCM layer because it is the nonpoloar than the reactants.
5) The Acid and the Base both can form the H-bonds with the water and dissolves in the aqueous layer.
6) The unreacted Acid can removed by the water wash (Aqueous layer) and Aqueous NaHCO3 solution wash. The Sodium bi carbonate solution is the basic in nature hence it can removes the unreacted Acid.
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