Combined 250 mg of 3,4-dimethoxybenzaldehyde and 200 mg of 1-indanone and then 5
ID: 975917 • Letter: C
Question
Combined 250 mg of 3,4-dimethoxybenzaldehyde and 200 mg of 1-indanone and then 50mg NaOH after.
Help me find the theo yield, and limiting reagent.
Reaction Combine 250 mg of 3,4-dimethoxybenzaldehyde with 200 mg of 1-indanone in a test tube. clean metal spatula, carefully mix and crush the solids together until a brown oil results. Take care that you do not break the test tube! 1. With a 2. Next, add 50 mg finely ground (mortar and pestle) Sodium Hydroxide (Hygroscopic! Do not let this touch your skin of course). Continue to mix and scrape the bulk material...which will soon form a solid again. Workup and Purification . After the mixture has solidified, simply let it stand undisturbed for 15 minutes. Meanwhile: 2. Transfer a small aliquot of your reaction mixture to a ceramic well plate and dissolve it in acetone. Do the same for the two starting materials (feel free to share), and use these solutions to spot and co-spot a silica plate for TLC analysis (4:1 H:E) After ~ 15 minutes, add roughly 2 mL of 10% aqueous HCl solution, and scrape the walls of the test tube to dislodge the solids. Use pH paper to verify that the solution is still acidic, adding more HCI solution as needed. 3, 4. Isolate the solid via vacuum filtration, then pull air through it for several minutes to dry it 5. Tare a small Erlenmever flask and transfer the crude material to it Record your crude yield. Begin to heat the crystallization solvent hot, use some to wash the residual crude product from the test tube into your crystallization vessel. Slowly, with stirring and warming, add minimal hot solvent to your crude product until you have JUST enough to form a clear yellow solution. Allow the solution to cool to room temperature (later transfer to an ice bath to maximize recovery if time permits), then collect the crystals by vacuum filtration and as above, pull air through the solid extensively 6. (90-95% aq. EtOH:-20mL or less). Once the solvent is 7. Characterization I. Calculate and record your theoretical yield, actual yield, and % yield. 2. Provide final TLC of SM vs crude vs pure, including the Rr values 3. Report the physical properties, color and mp range of your recrystallized product. Report the isolated mass and both % recovery (from crystallization) and % yield of final purified product. Submit your sample into the labeled class vial for your lab section. 4. Post-Lab Questions and Exercises. 1. Propose a mechanism for the conversion of starting material to product 2. Please suggest appropriate starting materials for the following three aldol reactions, For each of these, I'd consider first identifying the proper"-hydroxy carbonyl" intermediate. a "diketone starting material)Explanation / Answer
From the balance aldol reaction its clear that,
1 mole of 3,4-dimethoxybenzaldehyde react with 1 mole of 1-indanone to form 1 mole of dehydrated aldol product i.e. ,- Unsaturated ketone.
i.e. 166 g of 3,4-dimethoxybenzaldehyde react with 146 g of 1-indanone to form 294 g of ,- Unsaturated ketone product.
Hence we write,
166 g of 3,4-dimethoxybenzaldehyde 146 g of 1-indanone 294 g of ,- Unsaturated ketone product.
1)Limiting reagent determination:
We have ,
If, 166 g of 3,4-dimethoxybenzaldehyde 146 g of 1-indanone
i.e. 166 mg of 3,4-dimethoxybenzaldehyde 146 mg of 1-indanone …………. (see unit changes) ………. (1)
Then, 250 mg of 3,4-dimethoxybenzaldehyde (say) ‘A’ g of 1-indanone. ………………. (2)
Hence,
A = (250x146)/(166)
A = 219.9 g
It means for complete reaction,
250 mg of 3,4-dimethoxybenzaldehyde requires 219.9 mg of 1-Indanone.
But we have used only 200 mg of 1-Indanone. Hence 1-Indanone is the limiting reagent.
Note: It means reaction mixture will contain unreacted 3,4-dimethoxybenzaldehyde.
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2) With 1-Indanone as limiting reagent let us calculate theoretical yield (MT) of the product.
1-Indanone used is 200 mg let us rewrite correspondence equation for 1-Indanone and
If, 146 mg of 1-indanone 294 mg of ,- Unsaturated ketone product.
Then, 200 mg of 1-Indanone (say) ‘MT’ mg of ,- Unsaturated ketone product.
MT = (200x294)/(146)
MT = 402.7 mg of ,- Unsaturated ketone product.
Theoretical yield of the ,- Unsaturated ketone product i.e. reaction is 402.7 mg.
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