1. General

Review the following topics: recrystallization theory, vacuum filtration, ¹³C-NMR spectroscopy

2. Experiment

Safety note: Isopentyl nitrite (isoamyl nitrite) is a powerful heart stimulant. Avoid inhaling in the vapors. The compound should be handled under the hood and containers kept closed as much as possible.

The reaction has to be carried out in a 10 mL round-bottomed flask. Why?

In is important that both solids are dissolved in 1,2-dimethoxyethane first, before adding the isopentyl nitrite. Why?

The color change from purple to orange yellow occurs often gradually. If the solution remains purple, add 1-2 drops of pure isopentyl nitrite first and reflux for five more minutes. If this does not cause the color to change, add ~10 mg of the acid dissolved in ~0.5 mL of 1,2-dimethoxyethane.

The final product tends to dissolve and precipitate very slowly during the recrystallization process. Be patient when you add additional solvent to dissolve it. It might be a good idea to place a watch glass with ice on top of the Erlenmeyer flask. Why?

3. Things to think about

a. How would the ¹³C-NMR spectrum of tetraphenylnaphthalene (TPN) change if you lower the temperature of the solution?
b. Why is tetraphenylcyclopentadienone dark purple in color and while tetraphenylnaphthalene is white?
c. How do you explain the double melting point of TPN?
d. How do you calculate the e-value for a given wavelength? What does the e-value stand for anyway?
e. How many e-values should the student report in the postlab report?
f. Why is isopropanol ised as a solvent here?