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Williamson Ether Synthesis
Synthesis of 2-Ethoxynaphthalene
Experimental Procedure
(Provided as a handout)
Carey & Giuliano, pages 694-695
Apparatus
• 50 mL round bottom flask
• Reflux condenser
• Heating mantle
• Rubber tubing for reflux condenser
Carry out the reaction in your hood. Use care in handling Ethyl Iodide; it is a volatile, relatively
toxic compound.
Procedure
1.
2.
3.
4.
5.
To a 50 mL round bottom flask in the hood, add the following reagents in the order listed (swirl to
mix thoroughly after each reagent addition):
a. 5 mL of methanol
b. 2.0 g (0.014 mol) of 2-Hydroxynaphthalene (2-Naphthol or ß-Naphthol).
c. 2.7 mL (0.017 mol) of 25% NaOH solution. Do not allow the NaOH solution to touch
the ground glass joint of the flask. Use a funnel to add the NaOH.
d. 1.6 mL (0.02 mol) of ethyl iodide (d = 1.95 g/mL)
e. 2 boiling stones
Set up the flask and its contents for refluxing as follows:
H2O out
make sure this is open
a. Put the flask in a heating mantle (remember to put the
to the atmosphere and
heating mantle on a ring clamp which should be about 6 not stoppered
inches above the surface of the hood).
reflux
condenser
b. Insert the reflux condenser (with rubber hoses attached)
H2O in
into the round bottom flask and clamp the flask so that it
is sitting snugly in the heating mantle. The reflux
heating mantle
(plug into Variac)
condenser should be perpendicular to the hood surface.
c. Turn on the water to the reflux condenser (carefully!)
and make sure that the water in the condenser is cold
before you start to heat the flask.
d. Heat the reaction mixture to reflux it for 35 min. NOTE: be sure to plug the heating
mantle into the outlet connected to the Variac under the front edge of the hood. A setting
of 65 – 70 on the Variac should give a good rate of reflux. Remember to start the timing
for the reflux period when you first see liquid dripping from the reflux condenser.
After the 35 min reflux period is over, remove the heat source and allow the reaction mixture to
cool slightly.
Slowly pour the reaction mixture into a 125 mL separatory funnel containing 15 mL of cold water
and a little ice. Usually, two layers are formed with your product present as a dark liquid at the
bottom of the separatory funnel.
Rinse the reaction flask with ~ 3 mL of water and pour into the separatory funnel.
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6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
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Then rinse the reaction flask with 5 mL of ether and pour into the separatory funnel.
Add 15 mL of ether to the separatory funnel, stopper the funnel and shake it vigorously for 15
seconds total to extract the product into the ether layer (be sure to vent the funnel on occasion).
Remove the lower aqueous layer and discard.
Add another 10 mL of water to the separatory funnel, shake briefly and then drain and discard the
lower water layer.
In the following manner check the composition of your crude ether extract by TLC analysis using
silica gel TLC plates and a developing system of Ethyl Acetate:Hexanes (1:9). You may use a
250 mL beaker covered with a watch glass as your TLC chamber.
a. Using a TLC spotting capillary tube, place a spot of the 2-naphthol starting material
dissolved in ethyl acetate (this TLC reference solution is available in the community
hood) on the TLC plate.
b. Using a clean TLC spotting capillary, place a spot of the ether layer in the separatory
funnel next to the starting material on the TLC plate.
c. Develop the TLC plate using the Ethyl Acetate:Hexane (1:9) mixture and view the plate
under short wave UV light.
d. Is all of the starting material gone from your crude ether extract???
While the TLC plate is developing, place the ether layer remaining in the separatory funnel into a
50 mL Erlenmeyer flask. Add a boiling stone and carefully warm and continuously agitate the
flask on a steam bath to boil off the ether. After most of the ether is removed, vigorously heat the
liquid residue in the Erlenmeyer flask on the steam bath to remove the last traces of ether. Your
product will be present in the Erlenmeyer flask as a brown liquid.
After the ether is removed, allow the flask to cool briefly and then add 3 mL of 95% ethanol to the
residue in the flask. A transparent slightly-colored solution should be obtained.
Cool the flask in an ice bath. While the flask is cooling, continually stir and scratch the flask’s
contents with a glass stirring rod. Crystals should begin to form. Be patient! It may take 5 -10
minutes or longer before crystallization starts. Keep the flask in the ice bath for this entire
recrystallization process.
If no crystals form after 10 minutes of cooling and scratching, see your instructor or TA and s/he
will provide some seed crystals to attempt to initiate the crystallization process. Once the
crystallization process starts, cool and scratch (with a glass rod) the flask for an additional 5 – 10
minutes.
After no more crystals appear to be forming, use vacuum filtration to collect the solids on a Hirsch
funnel. Have ~ 6 mL of ICE COLD 85% (Note: 85% not 95%) ethanol ready before starting the
filtration. Be sure that you keep all mixtures and washes ice cold during the
recrystallization/filtration processes. If not kept cold, you will lose product!
Immediately after pouring or scraping out your product from the Erlenmeyer flask onto the Hirsch
funnel, use a 2 mL portion of your ice cold 85% ethanol to wash most of the crystals remaining in
your Erlenmeyer flask onto the Hirsh funnel. Use another 2 mL portion of 85% ethanol to quickly
(pour in one portion onto the crystals) give a final wash to the crystals on the Hirsch funnel. The
washing with 85% ethanol usually removes the brown color contaminating the product to provide
snow white crystals.
Allow the crystals to air dry on the Hirsch funnel by continuing to suck air through the crystals
until they appear to be dry and free flowing.
Weigh the crystals to determine your % yield.
Dissolve a few crystals of your recrystallized product in 10 drops of ethyl acetate in a test tube and
determine the purity of this material using TLC analysis as in Step 10. Are there any differences
in the TLCs when comparing your crude and recrystallized materials?
Take an infrared spectrum of your product; take a MP of the product and compare it to the
expected literature value.
How does the IR of your product compare to the IR of authentic 2-ethoxynaphthalene provided to
you as a handout?
Compare the IR and 1H NMR spectra of both starting material and product (provided as handouts);
interpret the spectra (including assignable NMR splitting patterns) and indicate key absorption
bands/peaks that distinguish between starting material and product. Hand in the spectra with
peaks labeled with your conclusions.
TMBare (2/9/2012)
DLZubris (2/2013)
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