1. General Comments

For those of you who were wait-listed, switched section or added to the class, the change should show up on your study schedule by Friday, April 8, 2016. Please keep in mind that the instructor has the right to refuse signing the drop form. Many students think that this is just a formality, but in reality the signature confirms that the instructor agrees with the student that it would be best to drop the course due to a hardship (Hint: not doing well is not a reason to drop the course!). The instructor will not sign any drop forms after meeting 6. No exceptions!

Make sure that you inform yourself on how to use the FTIR spectrophotometer (FTIR). The TA will demonstrate its operation during the lab section. You should have read the procedure already and be able to ask specific questions about things that are not clear to you before you attend to your lab section. Please make sure that you understand how to use equipment properly without breaking it.

Try to make yourself familiar with the electronic resources that are given to you on the course website. It will save you a lot of work in the library in terms of finding physical properties and safety related data.

You should have purchased a lab notebook (if you don't have one left from 30 AL), a flame-resistant lab coat, goggles and nitrile gloves before you enter the second lab. You can purchase them from the medical bookstore or AXE (YH 1275, note: they only except credit cards and have very limited business hours!). You will not be allowed to perform any work in the lab if you are not appropriately dressed. No exceptions!

It would probably be beneficial to read the infrared chapter in the reader as well. This will make it easier for you to understand the infrared part in the lectures to come. Aside of that, you will have to work on the infrared assignment very soon as well since it is due by Friday, April 8, 2016 at 12:00 pm.

2. Experiment

In the lab, a mixture of cis and trans 2-methylcyclohexanol (ration: ~47:53 according to GC) is used as reactant. Four different catalysts are going to be used this quarter (conc. H₃PO₄, p-toluenesulfonic acid, Amberlyst A15 and Montmorillonite K10), which will be assigned to you by the teaching assistant. The students will work in pairs in the lab for this experiment, but are required to provide an individual postlab report for the project. Each group should collect three different fractions (List of the possible alkene products)

It is very difficult to provide any specific setting for the hotplate because every hotplate has a slightly different heat output (there are many different models of hotplates with different ages). It also matters where the setup is located on the hotplate and how good the contact between the conical vial and the aluminum block is. The temperature of the hotplate should be as high as it is necessary to distill a milky mixture ( = methylcyclohexenes + water) over slowly (~60 minutes). A wet paper towel should be wrapped around the upper half of the Hickman head and the lower half of the air condenser to cool the glassware (Hint : The wet paper towel can be secured using the test tube clamp). However, excessive wrapping should be avoided (you are not preparing a mummy!) because the experimenter has to be able to observe what is going on inside the setup i.e., if the product collects in the Hickman head. Due to the heat radiation of the hotplate, the glassware will warm up quickly and the product will not condense anymore if the Hickman head is not properly cooled. The contact of the cold paper towel with the glassware is what counts here and not the quantity of paper towel!

The products are fairly volatile (b.p.= 100-110 ^oC, see link above). The storage vial has to be capped right away after the product is transferred from the Hickman head. However, the top of the air condenser cannot be closed with a cap or a septum because this will most likely result in an explosion first, a visit to the hospital second (at the very best) and lastly to an automatic "F"-grade for the course due to the fact that the student poses a safety hazard to him/herself and fellow students.

Only a small amount of anhydrous sodium sulfate should be added to the organic layer only (see chapter out about drying agents) after it was cleanly separated from the aqueous layer. Excessive amounts of drying agents usually complicate the separation of the liquid and the solid later on.

Nothing should be discarded before the final product has been isolated and positively identified by infrared spectroscopy, melting point, etc.

Hint: The most efficient way to get through this lab is to place the flask from the benzoin experiment in the ice-bath. While cooling the mixture, the student can set up the elimination experiment and get it started. During the distillation of the methylcyclohexenes/water mixture, the obtained precipitate from benzoin experiment is isolated via vacuum filtration.

3. Critical Thinking

a. What would happen if the temperature was set too high initially?
b. Why is it important that the distillation is performed slowly?
c. What is the proper arrangement of the spin vane in the conical vial? Explain briefly.
d. What remains behind in the conical vial after the distillation is completed?
e. What is the function of the saturated sodium chloride solution in the work-up?
f.  Why do the compositions of the three fractions differ from each other?
g. A student isolates a clear liquid after the distillation. Can he conclude that his experiment was sucessful?
h. What is the function of the 1,2-dimethoxyethane in the KMnO₄ test?
i. Why is the reaction with Amberlyst A15 and Montmorillonite K10 considered greener than the reaction with concentrated phosphoric acid?
j. How can the student determine if a peak is due to a cyclohexene or a cyclopentene derivative?