245 * Lab #10
Oxidation of Cyclohexanol to Cyclohexanone
This synthesis is a variation of the one in the text which employs chromic acid as the oxidizing agent. The oxidizer we will use will be 13% sodium hypochlorite.
Write a balanced equation for the oxidation of cyclohexanol by hypochlorous acid.
Procedure:
In a 125 mL Erlenmeyer flask containing a stir-bar, place 1.5 mL (measured precisely) of cyclohexanol (listed/flammable) and about 3.5 mL of glacial acetic acid (corrosive). Glacial acetic acid must be handled in the HOOD.
The resulting solution is cooled in an ice-bath. In small portions, with stirring , add 25 mls of 6% sodium hypochlorite (oxidizer). After addition, remove the ice bath. Stir the solution for 30 minutes. After at least 30 minutes, heat the flask to 60oC., keep it there for ten minutes and let it cool to room temperature.
Add small portions of solid sodium thiosulfate with stirring until the solution no longer tests positive on KI-starch test paper. This destroys excess hypochlorite.
To neutralize the acetic acid, anhydrous sodium carbonate (about 1.5 gm) is added in small portions, with stirring, to the solution until carbon dioxide evolution stops.
Add about a gram of sodium chloride to the aqueous solution. Now, using a separatory funnel, extract the water solution with two 5 mL portions of diethyl ether (listed/flammable). Given the high ionic strength of the aqueous phase, your product , cyclohexanone (listed), will dissolve in the ether phase.
Combine the two ether extraction's in a small beaker and dry with a spatula-tip full of anhydrous sodium sulfate as you've done in previous labs.
Do the following under a hood. Carefully decant (pour off) , or remove with a pipette, the ether/cyclohexanone mixture, putting it in a small pre-weighed vial. WARM (not heat) the vial on a hot plate set to "low". The last one mL or so that does not evaporate is the cyclohexanone (bp 155.6 degC). Reweigh the vial to obtain the yield.
Characterization is by refractive index, infrared
spectroscopy, and/or the synthesis of a derivative. Consult your
lab
instructor.
WASTE Spill & Disposal F: Cyclohexanol, Cyclohexanone
(listed), Ethyl
Ether & aqueous mixture. Labeled waste container will be in Hood
#5.
WASTE Spill and Disposal - E:
Any acetone used to clean glassware. *THERE IS AN ACETONE
WASTE BOTTLE IN THE HOOD.
DO NOT PUT USED WEIGH BOATS IN THE HW CHEMICAL CONTAINER. CONTAMINATED
PAPER
TOWELS AND WEIGH BOATS ARE PUT INTO THE CLEAR PLASTIC HW BOX IN THE
HOOD. PAPER
ENVELOPES W/CHEMICALS SHOULD BE FOLDED MULTIPLE TIMES AND SEALED BEFORE
BEING
PUT INTO THE SPECIFIED HW CONTAINER.
|
CHEMICALS: |
LOCATION |
|
cyclohexanol (1.5 mL) |
Hood #5 |
|
Hood #5 |
|
|
glacial acetic acid (3.5 mL) |
Hood #5 |
|
Sodium thiosulfate |
Org_prep |
|
KI-starch test paper |
Org_prep |
|
Org_prep |
|
|
Org_prep |
|
|
Org_prep |
|
|
Diethyl ether (10.0 mL) |
small refrigerator |
|
Waste Container |
Hood #5 |
Equipment:
Refractometer
Infrared Spectrophotometer (courtesy of AIST)
· IR