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 salicylic aldehyde prepared in the lab and chiral epoxides. The draft version of the paper is due on April 23, 2010 by 4:30 pm in YH 3077E.

2. Experiment

a. Jacobsen ligand

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

If you have to downscale the reaction, it is imperative to downscale the amount of solvent as well because the ligand exhibits a moderate 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 45 minutes is usually sufficient in order to complete the reaction. Most of the time, a yellow precipitate is formed in the beginning already, which requires efficient stirring to avoid bumping.

During the drying step, the washing procedure followed correctly: first water, then saturated sodium chloride solution and lastly the drying agent in the organic layer only (try to remove the aqueous layer as good as possible). The students will most likely 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 is water added to the reaction mixture before it is allowed to cool down?

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

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? What are the proper concentrations for each measurement?