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Experiment 19:

Experiment 19:. OXIDATION OF 9-FLUORENOL. 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.

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Experiment 19:

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  1. Experiment 19: OXIDATION OF 9-FLUORENOL

  2. 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 analyzethe purity of the product using TLC and melting point analysis. • To characterize reactants and products using IR analysis.

  3. Before coming to lab… • Review these techniques: • TLC analysis • Acid-base Extraction • Drying over MgSO4 • Melting Point Analysis

  4. Typical oxidation vs. Green oxidation Typical oxidation using chromium compound Greener oxidation using household bleach

  5. Forming the oxidizing agent… NaOCl + CH3CO2H  HOCl + CH3CO2Na Sodium acetic hypochlorous sodium Hypochlorite acid acid acetate • Sodium 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.

  6. CHEMICAL EQUATION From reaction of bleach with acetic acid!

  7. PROPOSED MECHANISM 1 3. Water abstracts a proton from the oxygen bearing the chlorine… 1. Bleach is reacted with acetic acid to produce hypochlorous acid. 2 3 2. Electropositive chlorine atom undergoes nucleophilic attack by oxygen of alcohol to form O-Cl bond… 4. …followed by another attack on the proton of the carbon bearing the oxygen. 4 5. Both electrons from the C-H bond form the p bond of the carbonyl, and a chlorine atom is eliminated to form the neutral product ketone. 5 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.

  8. OVERVIEW • React alcohol, acetic acid, and bleach dissolved in acetone to synthesize product. • Follow the reaction progress using TLC analysis. • Neutralize acid and perform extraction to purify product and isolate from unreacted starting materials. • Evaporate solvent to yield solid product. • To reweigh to obtain product mass and calculate % yield. • Perform melting point analysis to identify and determine product purity.

  9. Why are the Rf values different? 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!

  10. Why does the color change? More conjugated Less conjugated • 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.

  11. 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. Complete reaction!!! RCT STD YOUR RXN PROD STD

  12. EXPERIMENTAL PROCEDURE(PURIFICATION) • Transfer liquid to separatory funnel. • Extract product into diethyl ether 2X. • Wash organic layer with 5% NaHCO3 and Saturated NaCl. • Transfer organic layer to clean flask. • Dry over MgSO4. • Transfer liquid to preweighed 150 mL beaker w/3 boiling chips. 125 mL 150 mL

  13. EXPERIMENTAL PROCEDURE(PURIFICATION) • Prepare a tap water bath using your 400mL beaker. • Place the water bath on a hotplate and heat the water on a setting of 3 (NO HIGHER) until just above room temp. • Remove water bath from hotplate. • Slowly place the 150mL beaker containing diethyl ether into the water bath to evaporate the liquid solvent. • If the solution boils too rapidly, remove it immediately until it ceases to boil! 150 mL 400 mL

  14. EXPERIMENTAL PROCEDURE(PRODUCT ANALYSIS) • Place LABELED 150mL beaker in oven for 10 minutes to dry. Reweigh. • Repeat if %yield is greater than 100%! • Reweigh to obtain final product mass and calculate % yield. • Perform melting point analysis. YOUR NAME HERE

  15. Table 19.1

  16. Table 19.2

  17. Table 19.3

  18. IR Spectroscopy • Remember to concentrate on the types of bonds that indicate the CONVERSION from reactant to product! 3041 3196 1031 3060 1716

  19. Table 19.4

  20. SAFETY CONCERNS • DIETHYL ETHER IS EXTREMELY FLAMMABLE! NEVER place diethyl ether directly on a hotplate! • Acetic acid is corrosive!

  21. WASTE MANAGEMENT • “LIQUID WASTE” container: any/all liquid waste from extraction and TLC experiment. • “SOLID WASTE” container: any/all solid waste from synthesis and purification. • BROKEN GLASS box: Place used TLC and melting point capillaries.

  22. 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.

  23. LABORATORY NOTEBOOK(Pre-lab) • OBJECTIVE (Must clearly state…) • What compounds will be made and how • How the compounds will be purified • How the purity of the product will be determined • CHEMICAL EQUATION • Include the chemical equation from the top of page 161. • TABLE OF PHYSICAL DATA (Complete the following table using a site listed on WWW Links ONLY. Wikipedia is unacceptable!) • REFERENCE TO PROCEDURE (Must include…) • full title including edition and author names • page numbers where actual procedure can be found

  24. LABORATORY NOTEBOOK(In-lab) • DATA/CALCULATIONS • Initial weight of 9-fluorenol used • TLC diagram (s) with all cm measurements • Initial weight of 150 mL beaker • Final weight of 150 mL beaker + product • Final product weight • Physical state and color of product • Theoretical yield calculation • Percent yield calculation • Atom economy calculation • Cost per synthesis and cost per gram calculations • Give at least one TLC Rf value calculation • EXPERIMENTAL PROCEDURE • In paragraph form, describe the procedure that you actually followed during the lab. • Paragraph must be written in PAST TENSE, PASSIVE VOICE. • Include any volumes or weights of chemicals used during the experiment. • Include any observations or errors that occur (if any).

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