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Experiment_H

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					Organic Chemistry II Lab                                School of Science and Technology
CHEM 2212L (Fall 2008)                                  Georgia Gwinnett College


Experiment H. Oxidation of 4-Chlorobenzyl Alcohol to 4-Chlorobenzoic Acid


1. EXPERIMENTAL OBJECTIVES:

       a. Conduct an oxidation of an alcohol to a carboxylic acid.

       b. Isolate the product.

       c. Characterize and analyze.

       d. Present, analyze, and discuss results in a written report.

2. SPECIAL INSTRUCTIONS:

       a. Chemicals and solvents:
             (1) 4-chlorobenzyl alcohol, [873-76-7]
             (2) 4-chlorobenzoic acid, [74-11-3]
             (3) calcium hypochlorite, [7778-54-3]
             (4) glacial (pure) acetic acid, [64-19-7]
             (5) acetonitrile, [75-05-8]
             (6) diethyl ether, [60-29-7]
             (7) saturated sodium bicarbonate (aq), [144-55-8]
             (8) concentrated (12 M) HCl (aq), [7647-01-0]

        b. As you prepare your separation flow chart (which is critical for your success),
note that the "Work-Up, Isolation, and Purification" section of the procedures is analogous to
the extraction of benzoic acid from the three component mixture you accomplished in
Experiment C.

3. PROCEDURES:

Apparatus
1. In the first lab session you will run the oxidation reaction. Set up the reflux apparatus
with the cold-water condenser. Use the Al block for heating but do not turn on the hot plate
yet. Stirring throughout the reaction is critical, so ensure you have good stirring with your
set-up. Use the small bar magnet.

2. The second lab session is for work-up and isolation. You will use the Hirsch funnel to
isolate your final solid product. You will not recrystallize the product so you will not need
the Craig tube.

Setting Up
3. Confirm you have good stirring action. Make sure the heat is not turned on.




                                          Page 1 of 2                                 4/1/10
Organic Chemistry II Lab                                 School of Science and Technology
CHEM 2212L (Fall 2008)                                   Georgia Gwinnett College

Oxidation
4. Pay close attention to heating instructions. A very low setting on the Al block will give
the desired temperature. After the system has come to thermal equilibrium, you should use
the small thermometer to measure the temperature just below the condenser head but just
above the reaction mixture in the vial. Your target is 45-50 oC. Make slight adjustments to
your hotplate setting, but be mindful of not exceeding 45-50 oC. Good temperature (but not
too high or too low) and good stirring are critical. Heat for 1.5 hours max, then test solution
with starch paper (adding more oxidizer if needed).

5. You will continue stirring and heating for the remainder of the first lab session, about
another hour, but until about 4:30 at the latest. Let the apparatus cool, clean up, store your
labeled and capped vial in the prep hood until the next lab period. While the reaction is
ongoing, conduct IR analysis of the starting material (4-chlorobenzyl alcohol).

Work-Up, Isolation, and Purification
6. Begin chilling about 30 mL distilled water that will be used for rinsing your product.

7. Recall that extracting sequentially means add, mix, separate---then do it all again.

8. Add the concentrated acid slowly. Monitor the pH every few drops with scraps of pH
paper.

9. You will have to scrape and wash your centrifuge tube with cold water to get your product
transferred to the Hirsch funnel. Be careful not to swamp the funnel with liquid. Wash the
filter cake with several mL of cold water.

10. Place your solid product on a watch glass and dry under the “fries lamp” for a few
minutes. Do not recrystallize your product.

Analysis
11. Determine % yield.

12. Conduct melting point analysis. The product has a high melting point, typically outside
the calibration range of the apparatus.

13. Conduct IR analysis of starting material and product.




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