Question

After a brief search of the Toxicology Data Network and cross-referencing with the compounds you identified so far in lavender, you notice cineole, a known phytochemical used in pesticides. This chemical interests you as you read a paper published by Dr. Mitchell Erickson MD about this harmful pesticide being detected in breast milk from residents in Jersey City, NJ. You know that in low doses this chemical increases the absorption of chlorohexidine (a chlorine containing chemical used to disinfect skin before surgery) and other chlorinated chemicals by the activity of glucuronyltransferase, a key enzyme in drug metabolism and detoxification. You noticed this enzyme opens cineole's epoxide ring in an SN1 characteristic. This is advantageous to you since in it's epoxide form cineole cannot be easily seperated from water without decomposing it and an alcohol can be dehydrated in the presence of a strong acid and mild heating. Unfortunately, this newly converted cycloalkene exists at equilibrium with it's alcohol derivative. Propose a method to get the purified cyclolkene (there are several).

Answer 1

Chemical Tests to Distinguish Alkenes from Alkanes.
Often, simple chemical reactions can be used to detect the presence of a functional group. Here, you
will carry out two such reactions. Run the test reactions on your product and cyclohexAne side-by-side
to observe the results of a negative test. If you have an insufficient amount of product, scale down
quantities by a factor of two for example.
(1) Bromine in Dichloromethane. Caution; bromine is extremely hazardous to breathe and
causes severe burns if it touches the skin. A dilute bromine solution is used in this test so the hazard
potential is much less than if pure bromine were used. The solvent, dichloromethane, is also toxic and
must be kept in the hood. If you accidentally allow the bromine solution to touch your skin,
immediately rinse the contaminated area with a dilute aqueous sodium thiosulfate solution, which will
be stored near the bromine in the hood, then wash with soap and water. Carry out all operations with
bromine in the fume hood.
The bromine solution is reddish-orange. Bromine reacts with an alkene to form a colorless dibromide.
Thus, if a bromine solution is added dropwise to an alkene, the solution will decolorize until all of the
alkene has reacted. Alkanes on the other hand do not react with bromine in this way, so the very first
drop of bromine solution will cause a reddish-orange color to persist. (Alkanes do react with bromine
by a free radical mechanism initiated by light, but this reaction is much slower.)
The test: in the hood, add about 0.5 mL of your cyclohexEne product to a small test tube and about 0.5
mL of cyclohexAne to another small test tube. To each, add dropwise, with swirling, 3 - 4 drops of a
3% solution of bromine in dichloromethane. Record any observed color changes after addition of each
drop. Dispose of all wastes from this test in the Organic Liquid Waste container.
(2) Potassium Permanganate. Potassium permanganate is purple. It reacts with alkenes to produce a
colorless diol and a finely-divided brown precipitate of manganese dioxide. Under acidic conditions the
diol can further react to form a colorless dicarboxylic acid. Thus, when permanganate is added dropwise
to an alkene, the purple color disappears and a brownish suspension forms until all of the alkene has
reacted. Permanganate does not react with alkanes, so the first drop of permanganate added to an alkane
immediately results in a purple solution.
The test: add about 0.3 mL of your product cyclohexEne to a small test tube and about 0.3 mL of
cyclohexAne to another small tube. To each, add dropwise, with swirling, 2 - 3 drops of an aqueous
solution containing 1% potassium permanganate and 10% sulfuric acid. Record any observed changes
after addition of each drop. Dispose of wastes from this test in the Organic Liquid Waste container in
the hood.