The purpose of this experiment was to learn about metal hydride reduction reactions. Therefore, the sodium borohydride reduction of the ketone, 9-fluorenone was performed to yield the secondary alcohol, 9-fluorenol. Reduction of an organic molecule usually corresponds to decreasing its oxygen content or increasing its hydrogen content. In order to achieve such a chemical change, sodium borohydride (NaBH4) is used as a reducing agent. There are other metal hydrides used in the reduction of carbonyl groups such as lithium aluminum hydride (LiAlH4). Nevertheless, the latter is not used in this experiment since it is very reactive and extremely flammable. On the contrary, NaBH4 is relatively mild and it can be used with protic solvents. In this manner, 1.507 grs of the ketone 9-fluorenone were mixed with 30.0 ml of 95% ethanol in a 125 ml Erlenmeyer flask. The bright yellow mixture was stirred during 7 minutes until all the components were dissolved. It is important to allow the ketone to dissolve completely in the solvent in …show more content…
The yellow solution containing the reactants was slowly poured into the beaker containing the cold water and the acid in order to cause the precipitation of the alcohol, 9-fluorenol and to destroy (hydrolyzed) the unreacted excess sodium borohydride. Subsequently, the white precipitate was vacuum filtered and washed twice with 20.0 ml portions of distilled cold water by pouring the liquid into the Buchner Funnel during filtration. It was necessary to wash the alcohol prior to recrystallization considering that the C-OH bond is easily broken by the formation of a stable and benzylic carbocation that favors the synthesis of difluorenyl ether. Finally, before the purification by recrystallization of the obtained product, the white solid alcohol was allowed to dry over a period of a