You need the following, in this order:
- Title of experiment, name and date
- The reaction scheme for the specific reaction you are performing. No mechanism is included in the scheme. Underneath the structure of reactants write how much you are using, g or mg for solids, mL and density for liquids, also how many mmol of each you are using. Get this information from the procedure or online resources. Indicate in your scheme which reactant is limiting. Indicate in your scheme which product is the desired product and the theoretical yield in mmol and either g or mg. Add above or below the arrow any solvents and conditions for the reaction. All the reactants should be to the left of the reaction arrow.
- Prepare a table of reactants and products and their pertinent information. Column headings are name, structure, MF, MW (g/mol), density (if a solid the say NA), amount used for reactants (g or mg for solids, mL for liquids), mmol used, mmol expected for products, theoretical yield for products g or mg and hazards. Each reactant and organic product is a row in the table.
- Prepare a table of reaction solvents and workup solutions. The columns for this table should be name, structure, bp, density, purpose (be specific i.e. “removes H2O”, “removes ions”, “neutralizes” etc.) and hazards. All of the information for 3 and 4 can be found in the procedure or online. Sigma-Aldrich Catalog is a good source. Chemfinder is another option. You will need to know the mmol of zinc, allyl bromide, and benzaldehyde. Allyl bromide and benzaldehyde are the two major reactants. Which one is limiting? What is the theoretical yield?
- Obtain reference IR spectra for starting material and expected product. SDBS is a good source. You can also search online using the name along with the type of spectrum you are looking for. Organize IR data of the product(s) into table(s). For the IR table, the two column headings are structure and IR Diagnostic Bands (cm-1). The correct format for listing data in the second column is stretch, frequency range, descriptors. For example a broad, medium sp3C-H stretch from 2800 -3000 cm-1would be: sp3C-H, 2800-3000, b, m. You will be doing a full analysis of all non-fingerprint region bands of any acquired spectra.
- Obtain proton NMR spectra for the starting material and expected product. SDBS is a good source. You can also search online using the name along with the type of spectrum you are looking for. Organize the NMR information for the expected product into a table. You will need the structure of the product with the non equivalent H's labelled alphabetically. For each H set you will need chemical shift, multiplicity, J values if applicable and how many H are generating the signal.
- Draw out a formal curved arrow electron pushing mechanism for the reaction you are performing in the laboratory. You will need to show intermediates but not transition states. You can use chemical drawing software or copy and paste from a reference. If you have a reference be sure and cite it.
- Save the entire pre lab as one document. Also save as a pdf file and upload the pdf file.
4. Take the quiz. The quiz covers the readings and the prelab. A passing grade is 14/20. You have 3 attempts to pass the quiz. You need to prep for the quiz and have your materials with you when you take the quiz because you will have a 10 point deduction for every quiz retake. Do not retake the quiz if you have a 14 or higher.
Lab 12 Aldol Reaction During Lab
1. In a 50 mL Erlenmeyer flask equipped with a stir bar, dissolve 2.0 g of NaOH in 15 mL of deionized H2O.
2. To this solution, add 15 mL of ethanol.
3. In a separate beaker, combine 8 mmol acetone with 16 mmol benzaldehyde. Swirl well to homogenize the sample.
4. Prepare a TLC plate from this mixture. Determine the correct eluent mixture of hexanes and ethyl acetate to develop your plate.You are going to mintor the reaction progess by monitoring the decease in benzaldehyde.
5. Add the solution from step 3 to the Erlenmeyer flask slowly. Continue stirring the reaction mixture at room temperature for
6. While the reaction is running, monitor by TLC.
7. When the reaction is complete, chill the flask in an ice bath to 4 °C.
8. When the product has precipitated, collect it by vacuum filtration on a preweighed BÃ¼chner funnel.
9. Wash the filter cake with 10 mL of 95 % ethanol.
10. Wash the filter cake with 10 mL 4 % acetic acid in 95 % ethanol (v/v).
11. Wash the filter cake with 95 % ethanol. Fluff the solid to increase the surface area exposed to the air, and proceed to pull vacuum through the product for 10 - 15 minutes.
12. Obtain product mass by difference. Determine % yield.
13. Obtain a mp of your product. Prepare an NMR sample of your product and acquire a IR spectrum. of your product.
|Due By (Pacific Time)
||04/19/2015 12:00 am