Experiment 19:
OXIDATION OF 9-FLUORENOL
HOCl
OH
O
Objectives:





To synthesize a ketone from a secondary
alcohol using household bleach.
To monitor the reaction progress using TLC
analysis.
To purify product using simple extraction.
To analyze the purity of the product using
TLC and melting point analysis.
To characterize reactants and products
using IR analysis.
Before coming to lab…

Review these techniques:

TLC analysis

Acid-base Extraction

Drying over MgSO4

Melting Point Analysis
TYPICAL OXIDATION VS.
GREEN OXIDATION
Typical oxidation using chromium compound
Na 2Cr 2O7
OH
H2O, CH 3CO 2H, heat
O
Greener oxidation using household bleach
OH
NaOCl, CH3CO2H
acetone
O
THE OXIDIZING AGENT
NaOCl + CH3CO2H  HOCl + CH3CO2Na
Sodium
Hypochlorite
• Sodium
acetic
acid
hypochlorous
acid
sodium
acetate
hypochlorite is the main ingredient in bleach.
• It must first be converted to hypochlorous acid in
order to oxidize the alcohol.
• HOCl is a source of a positive Cl, which has 2 fewer
electrons than a chloride anion.
• Remember, oxidation is the loss of H or the addition
of O.
PROPOSED MECHANISM
HOCl
H3O+
H
Cl
O
- H2O
+
H
H
OH
H
O
H
Cl
O
- H3O+
Although complex, the mechanism
results in the exchange of a Cl+ with
a H+ on oxygen, followed by
subsequent elimination of HCl to
form the ketone.
H
H
O
O
H
H
Cl
H
- H3O+
+ H3O+
+ Cl-
O
A FEW THINGS TO CONSIDER…
HOCl
OH
O
The 9-fluorenol can DONATE
hydrogen bonds to the silica gel
on the TLC plate, resulting in a
lower TLC Rf value!
The 9-fluorenone can
ACCEPT hydrogen
bonds, but not donate
to the silica gel on the
TLC plate, resulting in
a higher TLC Rf value!
x
1
x
2
x
3
A FEW THINGS TO CONSIDER…
HOCl
OH
Less
conjugated
More
conjugated
O
• The more conjugated a compound is, the higher the wavelength of
light it absorbs.
• The visible region of the spectrum is the 400-700 nm wavelength
range.
• If a compound absorbs light close to 400 nm, it will appear as a
yellow color.
EXPERIMENTAL PROCEDURE
(SYNTHESIS)

Add Fluorenol to 50 mL flask with stir
bar.

Add acetone and stir of until dissolved.

Add acetic acid and bleach while
stirring. Place a small cork in top of
flask to reduce decomposition of bleach.

Stir 10 minutes.

Perform TLC experiment to check for
completion.


If oxidation is incomplete, add more acetic acid
and bleach, react for 10 additional minutes and
repeat TLC experiment.
If oxidation is complete, proceed to purification
steps.
x
1
x
2
x
3
EXPERIMENTAL PROCEDURE
(PURIFICATION)

Transfer liquid to separatory funnel.

Extract product into hexane.

Wash organic layer with 5% NaHCO3 and
Saturated NaCl.

Transfer organic layer to flask.

Dry over MgSO4.

Transfer liquid to preweighed beaker.

Evaporate solvent on hotplate.

Place solid in warm oven for 10 min.

Obtain final product mass, calculate %
yield, and perform melting point
analysis.
Table 19.1
Calculate based on 9-fluorenol
ONLY! Bleach is used in excess!

Theoretical yield (g)
Actual yield (g)
% yield
Melting Range (oC)
Product Appearance

compare to lit value of 81-85oC.
Record the physical state and
color of product.

Table 19.2
Should be calculated
based on 9-Fluorenol and
hypochlorous acid (HOCl).
 Review Experiment 13 for
calculation.

Atom Economy
Cost per gram
Remember to calculate
COST PER SYNTHESIS 1st
based on all reagents and
solvents!

Table 19.3
TLC Rf values
Compound
Standards
9-fluorenone

Rf values are UNITLESS!

Rf values are 2 decimal places ONLY!
If more than one TLC experiment is
performed, record data from final TLC
plate!

9-fluorenol
Sample
IR Spectroscopy
OH
O
9-fluorenol
to
concentrate on
the types of
bonds that
indicate the
CONVERSION
from reactant
to product!
9-fluorenone
• Remember
3196
1031
1716
Table 19.4
Functional Group
OH stretch
C-O stretch
C=O stretch
Base Values
(cm-1)
9-fluorenol
9-fluorenone
SAFETY CONCERNS
All compounds used in today’s
experiment are FLAMMABLE
and TOXIC! Use extreme caution
when in use!
•
WASTE MANAGEMENT




Place aqueous layer from extraction in container labeled
“AQUEOUS WASTE (Ketones)”.
Place TLC solvent in container labeled “ORGANIC
WASTE (Ketones)”.
Place used TLC and melting point capillaries in BROKEN
GLASS CONTAINER.
Place product in container labeled “9-FLUORENONE
(Student Prep).
CLEANING



Clean all glassware with soap, water,
and brush if necessary.
Rinse all glassware with wash acetone
before returning to lab drawer.
DO NOT return any glassware to lab
drawer dirty or wet.