Goal: The goal of this experiment is to reduce benzophenone to diphenylmethanol. This will be done using sodium borohydride and a methanol solvent. The product then should be recrystallized from hexanes and later distinguished by IR spectroscopy and melting point (1). Reagent Table
Compound Name and Structure Molecular Weight (g/mol) Mass (g) or Volume (mL) Melting Point (°C) Boiling Point (°C) Density (g/mL) Safety Hazards
Benzophenone
182.2179 5.51 g 48.5 305.4 1.1 Health, fire, explosion, and skin
Sodium Borohydride
NaBH4 37.83 1.0 g 400 500 1.07 Skin, inhalation, eye, and ingestion
Diphenyl-methanol
184.24 N/A 69 298 1.103 Fire, skin, inhalation, and eye
Methanol Solvent
MeOH 32.04 50 mL -97.6 64.7 0.792 Fire, explosion, inhalation,…show more content… The solution started to fizz rapidly, and then it slowed down after about 10 minutes as more NaBH4 was added. Next, when the previously created solution was heated over a steam bath, it boiled vigorously. Later, during the addition of 6M HCl, after enough HCl was added, the litmus paper turned bluish black when the solution was dropped on it. Then, when the 50 mL of diethyl ether was added, a white milky colored precipitate formed. After that, when the water was added the precipitate dissolved and two layers formed in the flask, the bottom one looking watery. After many steps, the organic layer solution was heated on a steam bath and this caused very violent bubbling. Once the bubbling stopped, 10mL of product was left in beaker. This product solidified, when removed from the steam bath and left to cool, into a white-gel like solid. During the recrystallization of the crude solid, the solid began to dissolve. However, not all of it dissolved. Once vacuum filtrated, the final product was left to cool, and this caused white crystals to crash out. These crystals weighed 4.03g. Lastly, the melting point was measured to give a range of 64.0-64.6 °C. The IR spectroscopy was analyzed, and it showed a broad peak at 3341 and another peak at 3023, along with other peaks that are shared with the starting materials…show more content… The NaBH4 was carefully measured and transferred with a watch glass on top because it is a highly caustic fine powder (1). Then, the NaBH4 was added slowly to the benzophenone solution to prevent the reaction solution from foaming out of the reaction flask, and the hood was kept down because hydrogen gas was being formed (1). The fizzing seen during this processes was the hydrogen gas escaping. When the fizzing slowed down, that was when the reflux apparatus was set up. The extra methanol was added around the edges to prevent freezing of the joints. Once the heating began, there was vigorous boiling, so it was important to have the boiling stones in there to prevent bumping. The condenser then stayed assembled when cooled so that the HCl would be added through it. Before it was added, it was dropped on the litmus paper to ensure that it is acidic. The HCl was added slowly so that only the minimum amount of HCl was added to quench the reaction solution. Once ether was added to this solution, a white precipitate formed. This was boric acid that had been formed during the quenching process (1). The water was then added to dissolve the boric acid and to create two separate layers, which it did. The top layer was the organic layer, since the ether is less dense than water. Due to this fact, the isolation process took