1. General

Review the following topics: NMR spectroscopy, Infrared spectroscopy, Recrystallization, Flash chromatography

2. Experiment

Safety notes: Concentrated phosphoric acid and acetic acid anhydride are very corrosive.

In the initial stage of the reaction, ferrocene is dissolved in acetic acid anhydride. The reaction mixture is then heated to 80-85 ^oC on a water bath after the conc. phosphoric acid was added slowly (dropwise). Higher temperatures and longer reaction times usually lead to a lot of side reactions!

After the reaction is completed, the reaction mixture is poured into sodium acetate solution. If the pH-value is too low, the pH has to be adjusted to pH=5-7 using sodium bicarbonate (Careful!). It is highly advisable to use a large beaker here (~400 mL).

The solution is very dark red (or brown) at this point, which makes it difficult to observe the phase separation. Depending on the conditions, it can also take some time to observe a phase separation.

The crude product is purified by column chromatography. Initially, only petroleum ether (What is this anyway?) is applied to the column to wet the column and to elute the unreacted ferrocene off the column. Afterwards, about 7% (not more!!) of ethyl acetate is added to the eluent to increase the polarity of the mobile phase and elute the mono-acylation product off the column.

Important: When applying the crude product to the column, the entire sample should be applied, and not only a small portion. Also, the polarity of the solvent used for this step should be as low as possible (why?)

In some cases the tip of the burette clogs up. In order to minimize this problem, the tip should be rinsed regularly with a little EtOAc to remove the deposited solid. In addition, it is also helpful to place the tip in the upper part of the test tube to immerse it in the solvent vapors which also reduces the evaporation of the solvent. This problem often occurs when the elution is too fast or too slow.

The fractions containing the final product are combined and the solvent removed without overheating the sample. Any impurity in FcOAc causes problems in the next project. Try to isolate as much as possible FcAc in order to have sufficient starting material for the independent project.

Note: Fc stands for "Fe(C₅H₅)(C₅H₄)"