1. General

At this point in the quarter, it would be very advisable to review your IR and NMR notes from lecture. You are expected to have mastered these topics by the time the final exam comes around. You will need to memorize the most important numbers and trends for the exam since there will no tables provided!

Note for the teaching assistant: the students should start the reflux first and can take the test during this period of time

2. Experiment

Safety note: Concentrated sulfuric acid is very corrosive. Wear nitrile gloves when you transfer it! Avoid spills on your clothes since it will ruin them!

For this week's experiment it is important that the glassware is dry. Why?

The alcohol should be used in a five-fold excess (in terms of moles) as compared to the carboxylic acid. Why?

After the reaction, the aqueous layer and the organic layer should be separated. The aqueous layer is then extracted with two portions of diethylether. The organic layers are combined and then carefully extracted with sodium bicarbonate in the conical vial or centrifuge tube. In the beginning, the two layers are mixed with a spatula or a small glass rod (especially the first time!). At this point it is very important to vent the container frequently. Why?

The amount of the drying agent used should be minimized in order to minimize the loss of compound.

Before the vacuum distillation can be carried out, the ether has to be boiled off at ambient pressure. Why? This can be done in a small beaker or the conical vial if the amount of the liquid is relatively small. If you only have a small amount of crude product, pre-weigh the Hickman head before the vacuum distillation.

The product has to be characterized using refractive index and IR by the student. The remaining sample is submitted to the TA in a properly labeled vial (your name, the combination, your TA and section) so that the instrumentation TA can acquire the NMR sample for you .

3. Things to think about

a. Why is an excess of acetic acid used and not an excess of isopentyl alcohol if you were to prepare isopentylacetate?

b. Does the esterification go to completion? If not, how can the yield of the ester be improved using the same reagents?

c. Why are esters very important compounds in industry?

d. Why do you have to wrap a cold paper towel around the air condenser?

e. Why do you have to heat the mixture to a boil?