Part I: TLC of the crude and final product
Since there is no solvent given in the procedure, you will have to figure one out for yourself. The lab support will provide several solvents for the task: hexane, toluene, dichloromethane, methanol. You will have to place four spots on your TLC plate: benzoin, the reference compound, the crude and the purified product. Ideally, the Rf-values should vary by 0.3-0.4. This might be accomplished using one solvent or a solvent mixture.
Part II: Clean-up of your drawer and the lab
Part III: NMR simulations (dry lab!)
The assignment is done during the second half of the lab period in YH1044 or SLC.
Using ACD labs Software, simulate and analyze som eof the the spectra for the following compounds.
Generating the molecules
In order to draw these compounds, you will have to use ChemSketch (the drawing modules of the software). Try to make use of the existing templates available in the program e.g. benzene, cyclopentane, etc. Otherwise, the drawing process is similar to the one in Spartan. However, you cannot draw the molecule in Spartan and then copy it over!
To expand an area, push both mouse buttons. A crosshair appears on the screen and a second screen on the top. Define the left edge by moving the cursor to the left side and clicking the left mouse button. Then hold the left mouse button and drag the cursor to the right and click again. A dark gray field will move with the cursor to highlight the area to be expanded. Alternately, you can also drag the markers on the top window to define the range.
1H-NMR spectra:
1. After you draw the molecule, generate the proton spectrum (ACD/labs 1H-NMR Spectrum Generator) of the compound (the default frequency should be 400 MHz at this point). Analyze the splitting pattern of the spectra and compare them with what you would expect to see.
2. Compare the spectra of isopentylacetate with the one given in the reader.
3. Next, change the Default Basic Frequency (Options Menu) to 60 MHz and Recalculate the spectrum. What changes? How can you explain the change?
4. Activate the Integration feature in the Tools-menu. Can you account for its shape and the steps observed?
5. Measure the coupling constants in m-chloro isopropylbenzene. Can you explain the multiplet patterns?
13C-NMR spectra:
1. You can similate the 13C-NMR spectrum in the fashion (ACD/labs CNMR Spectrum Generator). Compare the different substitution patterns in the 13C-NMR spectrum of the molecules in group 2. (All generated spectra are proton-decoupled.)
2. If you check the "Off-Resonance" feature (in the Tools-Menu), the decoupling feature is deactivated. How do you the spectra change? Which conclusion can you make from this type of spectra?
3. Prepare a solution of 100 mg of isopentylacetate in 1 mL of CDCl3. How does the spectrum look like? Then change the concentration to 5 mg/mL CDCl3 and 200 mg /mL CDCl3. Which changes do you observe in the spectrum?
4. Compare the simulated 13C-spectra of isopentylacetate with the one given in the reader.