1. General

Review the following topics: IR spectroscopy, polarimetry

Don't forget to start writing your formal report. By now, you should be able to write an introduction that contains an alternate synthesis for the aldehyde and chiral epoxides. The draft version of the paper is due on October 28, 2005.

2. Experiment

a. Jacobsen ligand

The potassium carbonate has to be dissolved first before the aldehyde is added. This is very important to avoid possible side reactions.

You should use your own aldehyde whenever possible. If you did not get a crystals by now, check the residue using IR spectroscopy and TLC. If the oil contains significant amounts the aldehyde, use your own material. Just use a little more than the procedure asks for. Just don't use all of it so that you have something left to characterize it as well.

If you have to downscale the reaction, it is impartive to downscale the amount of solvent here. The ligand has a reasonable solubility in ethanol.

Make sure that you set the temperature to a gentle reflux and do not forget to stir it.

A reflux period of 30-45 minutes is usually sufficient in order to complete the reaction. Most of the time, a yellow precipitate is formed in the beginning already.

During the drying step, make sure that the washing procedure followed correctly: first water, then saturated sodium chloride solution and last the drying agent in the organic layer only (try to remove the aqueous layer as good as possible). We will use a rotavap to remove the solvent. If the lines are too long, remove the solvent on the hotplate like before.

For procedure how to use the polarimeter see last page of reader and link.

3. Thing to think about

a. Why do you add water to the reaction mixture before you allow it to cool down?

b. How many signals do you expect to see in the ¹³C-NMR spectrum of the ligand?

c. How does the polarimetric measurement help to establish the absolute configuration and purity of the ligand?

d. Which solvent is used for the polarimetry and the UV-Vis measurement?