Experiment: Aldol Condensation
Week 7

• Is the product, tetraphenylcyclopentadienone, more soluble in ethanol or toluene? Why?
  
  
• Referring to the carbon-NMR on page 34 of your reader, can you account for the appearance of all of the peaks?
  
  
• If a carbon-NMR of the product were taken at very low temperatures (below -50 degrees Celsius), the appearance of the spectrum would differ significantly from the one of p. 34 of your reader. Why?
  
  
• Would the presence of water at the start of the reaction help or hinder the aldol condensation? Why?
  
  
• COLUMN CHROMATOGRAPHY:
  
  By now you should understand the principles of Thin Layer Chromatography (TLC). You know that TLC can help you identify the different components present in your product mixture. You also know that the distance that each component travels heavily depends on: 1) polarity of the components; 2) polarity of the solvent mixture. Now imagine running a 3-dimensional TLC plate, but upside down. Consider the following graphic:
  
  
  
  
  
  What you see above is a chromatography column. It is a glass cylinder with a bulb and ground glass joint on top and a tapered joint with stopcock at the bottom. Using the same principles as TLC, the chromatography column can, with the utilization of the proper amounts of silica gel, size of column (diameter and length), and type of solvent system, separate various components based on their respective polarities. With the aid of air pressure from the top, one may collect solvent fractions from the column that contain isolated components (purified).
  
  This technique is a must for every experimental organic chemist and is one of the most widely used ways to purify compounds from undesired side products.
  
  If you would like to know more about column chromatography, I'd be more than happy to explain. E-mail me here.