Oxidation of Cyclohexanol to Cyclohexanone
There are four basic types of chemical reactions in organic
chemistry: combination, elimination, substitution, and
rearrangement. Today, you will be conducting a
reaction in which you will convert cyclohexanol into
cyclohexanone (oxidation). Although some of the finer points of
this reaction are not totally understood, it is generally agreed that
it proceeds as follows:
As you will no doubt recall from general chemistry, oxidation/reduction
reactions involve the shifting of electrons from one species to
another. The species that losses electrons is said to have been
oxidized and is therefore the reducing agent. The species that
gains electrons is said to have been reduced and is therefore the
oxidizing agent. Like any other type of chemical reaction there
must be mass balance, so the number of electrons lost by one species
must equal the number of electrons gained by another. In organic
chemistry, the species being oxidized shows a loss of hydrogen and/or a
gain in oxygen, while the species being reduced shows a loss of oxygen
and/or a gain in hydrogen. You need to prove to yourself that
these two views are complimentary.
Our oxidation of cyclohexanol begins by generating the hypochlorous
acid which will be our oxidizing agent. As you can see from its
formula, the chlorine in hypochlorous acid has
an oxidation state of +1. Recall that chlorine normally has an
oxidation number of -1. This deficiency of electrons makes this
particular species very reactive. Since this is a very strong
oxidizing agent, we will be generating it in situ through the reaction of
acetic acid and sodium hypochlorite (regular household bleach).
In the next step, the hydrogen on the hypochlorous acid undergoes
nucleophilic attack by the oxygen of the cyclohexanol to form
protonated cyclohexanol and a hypochlorite ion. This is
followed by nucleophilic attack by the hypochlorite ion and
displacement of water. The water then abstracts a hydrogen which
initiates a cascade that results in the chlorine leaving as chloride
ion and the generation of cyclohexanone.
Note that the actual
oxidizing agent was Cl+ which was reduced to Cl-.
It is also interesting to note that the oxygen atom on the
cyclohexanone is not the same oxygen atom that was initially
present on the cyclohexanol. Where did it go, and how do you
think you could prove this?
The purpose of this lab
is produce cyclohexanone through the hypochlorite oxidation of
As before, you will use gas chromatography (GC), refractive index (RI),
and infrared spectrometry (IR) to
determine the purity of your product. In addition, you will
produce a specific derivative of your product to prove its identify.
Before you come into lab, make sure you have filled in your table of
reagents and products. You will need these values to determine
the identify of your products and to calculate your final
yield. You will also need to come to lab with IRs of both
cyclohexanone already in your notebooks (this link may be helpful:
Finally, it is important that you know exactly what you are going to be
doing so you can work more efficiently.
- Accurately weigh approximately 10 g of cyclohexanol into a clean,
dry 500 mL round bottom flask.
- Add 2-3 mL of glacial acetic acid, and a magnetic
to the round bottom flask.
- Fit the flask with a Claisen adapter and insert your thermometer
into the side arm of the flask (see figure above).
Position the thermometer so it is immersed but is not hit by the
magnetic stirring bar. Remember to
lubricate all ground glass joints with a minimal amount of silicon
grease. Make sure that all joints are secured (blue clips) and
that the whole apparatus is properly clamped.
- Fit a 250 mL separatory funnel onto the Claisen adapter (see
figure above) and add 180 mL of commercial bleach to it. The
concentration of commercial bleach will vary, but is typically about
- Support your apparatus on a magnetic stir motor and adjust the
speed of the motor so that the contents of the flask are stirred
- Add the bleach drop wise but as rapidly as possible to the
flask. The addition should take about 10-15 minutes.
Monitor the temperature as the reaction proceeds.
stirring the flask after the addition is complete for an additional
- Transfer the reaction mixture to a 400 mL beaker.
- Add approximately 50 grams of NaCl to the mixture and heat to 50
°C on a hot plate. Keep stirring the mixture for 5-10 minutes.
- Allow the excess NaCl to settle out and transfer the liquid to a
250 mL separatory funnel.
- Extract with 25 mL of hexane. Use proper technique and
beware of gas pressure!
- Transfer the hexane to a 100 mL beaker.
- Extract the reaction product with an additional 15 mL of fresh
- Add this hexane to the previous extract and dry them with a small
amount of anhydrous MgSO4.
- Carefully transfer this dried hexane to a 250 mL round bottom
- Attach the round bottom flask to the rotary evaporator and strip
off the hexane. Remember to note the rotary evaporator conditions.
- Determine the mass and purity of your product (micro boiling
RI, and FTIR). Be sure to include your GC and FTIR traces in your
- Turn in your product in a labeled, tightly sealed
container. Be sure to include the following information on the
- Calculate the theoretical, actual, and percent yields for
- Use your GC data to calculate the purity of your
- Use your RI data to calculate the purity of your
- Compare your boiling point with the literature value, what does
this say about the purity of your product?
- Compare and contrast your FTIR versus the literature IR for
(Updated 12/22/03 by C.R. Snelling)