1. General

Review the following topics: esterfication, IR spectroscopy, NMR spectroscopy

2. Esterification

Safety note: Concentrated sulfuric acid is very corrosive. Wear nitrile gloves when you transfer it.

It is very important that the benzoic acid is very dry. If you are not sure about it, place it under the heating lamp for 15 minutes to dry it a little more.

Do not overheat the mixture, because it will char (turn black) due to decomposition of the benzoic acid. A gentle boil is enough to get the reaction going. A water jacketed condenser should be used here!

During the extraction, make sure that you think about first which layer contains your product. If you do not observe a phase separation, add more water. If necessary, transfer the mixture into a small separatory funnel. However, this should be avoided as much as possible since this will ultimately cause a significant loss of product.

The extraction of the organic layer with sodium bicarbonate should be continued until no more carbon dioxide forms. Why?

It is very important to remove the alcohol from the reaction mixture, because many alcohols and nitric acid form unstable alkyl nitrites (http://www.ilo.org/encyclopedia/?doc&nd=857300059&nh=0).

3. Nitration

Safety note: Concentrated sulfuric and nitric acid are very corrosive. Wear nitrile gloves when you transfer them. Do not spill these chemicals on you anywhere.

The ester has to be dissolved in concentrated sulfuric acid first before the acid mixture is added.

Make sure that you cool the mixture in an ice-bath. The acid mixture has to be added dropwise. Why?

If you obtain an oil after you poured your reaction mixture on ice, add more ice and some water and keep mixing until the mixture solidifies.

Do not use an excessive amount of methanol (even if it is cold) to wash your crude product. You will lose significant amounts!

The crude product is recrystallized from a solvent mixture of MeOH:water = 4:1 and not 1:4!

4. Thing to think about

a. Why do you reflux the mixture in the esterification experiment?

b. Why do you use sodium bicarbonate during the work-up of the esterification mixture? Could you use sodium hydroxide as well?

c. Why do you have to control the temperature of the reaction mixture in the nitration reaction very carefully?

d. What are other methods to generate a nitronium ion?

e. What would happen if the student attempts to recrystallize the crude nitration product from a solvent mixture MeOH:water = 1:4?