1. General Comments

For those of you who were wait-listed or switched section, the change should show up on your study schedule by Monday, August 11, 2014. 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 read up on how to use the FTIR instrument (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 web site. 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 on Friday, August 15, 2014 at 4:30 pm.

2. Experiment

Safety note: Concentrated phosphoric acid (85 %) is very corrosive, possess a high density (r=1.88 g/cm³) and high viscosity.

If the cyclohexanol solidifies in the syringe, do not panic. Just warm the syringe and needle gently until it melts.

Change in procedure:

Use equal amounts of cyclohexanol and concentrated phosphoric acid in the experiment. Stir the mixture for 5 minutes before starting to heat it.

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 ( = cyclohexene + water) over slowly (~45-60 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 it is not properly cooled. The contact of the cold paper towel with the glassware is what counts here and not the quantity!

The final product is volatile (b.p.= 83 ^oC). The storage vial has to be capped right away after the product is transferred from the Hickman head. It might be a good idea to store it in an ice bath to minimize the loss due to evaporation. 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.

The second distillation has to be performed slowly as well in order to be able to separate cyclohexene and cyclohexanol. Please note that it makes absolutely no sense to distill the entire crude because this would not result in any separation!

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 cyclohexene/water, 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 during the first distillation? What distills over during the first distillation?
b. What remains behind in the conical vial after the first distillation?
c. What is the function of the saturated sodium chloride solution in the work-up?
d. What is the proper arrangement of the spin vane in the conical vial? Explain briefly.
e. Why does the sodium sulfate have to be removed before you distill the crude product again?
f. Why is it poor procedure to distill to dryness in the second distillation?
g. A student isolates a clear liquid after the second 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 concentrated phosphoric acid very viscous?