Sodium Borohydride Reduction of 9-Fluorenone

Sodium Borohydride Reduction of 9-Fluorenone Purpose: The main point of this experiment is to enhance the learning of hydride reduction reactions, by reducing 9-fluorenone (which is a ketone) to 9-fuorenol (an alcohol), through the use of sodium borohydride. Introduction: Metal hydrides are agents used for the reduction of carbonyls, and they cause different reactions depending on the functional group being used. As of today, the most important agents are Sodium borohydride (NaBH4) and Lithium aluminum hydride (LiAlH 4) and they are both different. Lithium aluminum hydride is more reactive and will quickly reduce reduces aldehydes, ketones, carboxylic acids, esters, and amides. While, Sodium borohydride is less reactive than the agent previously mentioned and will reduce aldehydes and ketones into alcohols. Through this experiment, Sodium borohydride and 95% ethanol will be used to dissolve the ketone 9flurorenone and once the yellow color has disappeared it means the reaction has been completed and the reduction product 9-fluorenol has been obtained. Due to its structure and the reactive hydroxyl group, it can be converted from 9-fluorenol to di-fluorenyl ether by boiling with mineral acid. Mechanisms: During this experiment 9-fluorenone, 95% ethanol and Sodium borohydride were mixed to obtain a reduction. Once they were all mixed and stirred the yellow color is supposed to disappear, however, ours did not turn clear, reason for which more Sodium borohydride was added while constantly stirring. Once it turned colorless and we added the HCl we noted how gas was released followed by the mixture of substances. We were able to filter the solid and remove as much water as possible. For the recrystallization we used 5 mL of water and 15 mL of alcohol and our solution became cloudy. After vacuum filtration our product was able to dry for 2 weeks (given that after one week it was still wet) in order to get the melting point. Data/Results: MP range of product: - 1st trial: 143.9 - 146.5 = 145.2 ºC - 2nd trial: 142.1 – 146.0 = 144.05 ºC Mass of product: 4.015 gram % Yield: 267.6% Conclusion: To conclude, the objective of this experiment was to obtain the melting point of 9-fluorenol and at the same time percentage yield. Based on the literature, the theoretical melting point of this reaction is 153 ºC, however, after waiting two weeks and attempting to get melting point twice the results we obtained were between 144.05 – 145.2 with a percent yield of 267%. Clearly, these were not the expected results and it shows errors may have occurred during this laboratory. Based on our results, when percent yield exceeds or is greater than 100% it might indicated that the product was still wet or also it could contain impurities. This could be due to an error during recrystallization such as not waiting the necessary amount of time for the product to cool down, this mistake causes the product to be impure even after filtration, due to its elevated temperature. Even though our product was able to stay drying for three weeks, it never reached the level of dryness required in order to obtain the literature melting point. A. RESULTS 1. Name of Limiting Reagent: Fluorenone 2. Grams of Limiting Reagent: 1.5 grams 3. Moles of Limiting Reagent Used: 0.0083 moles 4. Name of Organic Product: 9-Fluorenol 5. Theoretical Yield (moles): 0.0083 moles 6. Theoretical Yield (grams): 1.5 grams 7. Actual Yield (grams): 4.015 grams 8. Actual Yield (moles): 0.022 moles 9. Actual Yield (mL – if liquid): N/A 10. % Yield: 267.6% 11. Typical % Yield Expected: 80% (1.2 grams) 12. Literature Melting Point: 153 ºC 13. Experimental Melting Point Range: 144.05 – 145.2 ºC 14. Color: White 15. Literature nD (if liquid): N/A B. Balance chemical equation C. Conclusions 1. Was the compound that you synthesized pure? Explain - Our compound was not pure given its melting point, which was different than the literature melting point. 2. Compare your yield with the typical yield expected - Our yield was much more higher than the expected one. As mentioned in my conclusion, it may have been because the compound was wet which led to impurities.