Synthesis of Adipic Acid
Oxidative cleavage of alkenes is a well known reaction. Several reagents are known to react with
alkenes which result in complete breaking of the both bonds to the carbon
atoms. Depending on the reagents chosen,
different oxidation states can be achieved.
For example, the reaction of an alkene with ozone followed by zinc
results in the formation of two aldehydes. Reaction of the same alkene with potassium
permanganate under basic conditions results in oxidation to the carboxylic
acid. It is this latter
type of reaction that will be investigated in today’s experiment.
The purpose of this experiment is to synthesis adipic
(hexanedioic)acid through the permanganate
oxidization of cyclohexene. This is actually a very complicated redox reaction and the mechanism is not well understood,
however, the stoichiometry is as follows:
Adipic acid is an important
commercial product, since it can be reacted with
1,6-hexanediamine (hexamethylenediamine) to form the
first commercially successful polymer: Nylon-6,6.
Before you come into lab, make
sure you have filled in your table of reagents and products. You will
need these values (particularly the molecular formula and molecular weight) to
determine the identity of your products and to calculate your final
yield. Obtain IR's of cyclohexene and adipic
acid from the SDBS web as part of your pre-lab activities. Make sure you understand the each step of the
procedure before arriving at the lab.
approximately 50 mL of water, and 9 g of potassium permanganate to a 250
mL Erlenmeyer flask.
the volume required to achieve 1.6g cyclohexene and add the appropriate
volume via a graduated pipet.
Cyclohexene has an objectionable odor, so keep it contained in the
hood or under your snorkel hood.
- Add a
magnetic stirring bar and your thermometer to the flask and place on a
magnetic stirring motor.
the motor for vigorous stirring, but DO NOT allow it to splatter.
5 minutes, check to see if the flask feels warm. If not heat it to
about 30 °C.
stirring and heating for another 30 minutes. The temperature of the
mixture needs to be maintained between 35 °C - 40 °C. If it rises
above 45 °C, place the Erlenmeyer flask in
an ice bath briefly.
the temperature of the flask to 55 °C - 60 °C and continue to stir for
another 30 minutes. DO NOT allow the temperature to approach the
boiling point of cyclohexene.
for the presence of excess permanganate by withdrawing a drop from the
reaction mixture and touching it on a paper towel. If you see a
purple ring around a brown center (manganese dioxide), permanganate is
permanganate is still present, add approximately 1 mL of methanol and heat
and stir for several minutes. Repeat until permanganate is no longer
present. Note, this step is very exothermic.
the hot mixture using a Buchner funnel into a CLEAN filter flask.
the Erlenmeyer flask with 10 mL of hot 1% sodium hydroxide solution and
pour through the filter.
with a second portion of 10 mL of hot 1% sodium hydroxide solution. The
filtrate should be clear and colorless, if not refilter.
the filtrate and washing into a 150 mL beaker that has been pre marked at
- Add a
boiling chip and boil off the water until less than 10 mL remain.
the solution to room temperature and then place it into an ice bath. Let
it cool to well below room temperature.
add 10 mLs of concentrated hydrochloric acid and
allow the beaker to stand in the ice bath for as long as possible (minimum
of 15 - 20 minutes). Your yield is largely determined by how long you let
it cool at this stage.
vacuum filtration to collect the product.
the crystals in an 110 °C - 125 °C oven for 10
minutes. Weigh the product and
return to the oven for an additional 10-15 minutes. Repeat until a constant weight is
the melting point of your product. Note how it compares to the literature
your yield, purity (m.p., and FTIR), and turn in
the product in a properly labeled vial:
Actual Yield (g):
Theoretical Yield (g):
the theoretical, actual, and percent yields of your product.
pure is your product? How can you tell?
was the methanol added? Did it have any effect on your yield or
- Give a
detailed analysis of your FTIR. How does the product compare with
the starting materials?
by C.R. Snelling)
(Updated 2/1/09 by J. Neilan)