REDUCTION OF BENZOPHENONE WITH SODIUM BOROHYDRIDE

This experiment aims to reduce the aromatic benzophenone to diphenylmethanol (Benhydrol). Sodium borohydride (NaBH₄) is used as the reducing agent. It is a mild reducing agent that converts aldehydes and ketones to alcohols. Reactions involving Sodium borohydride are carried out in isopropanol, methanol or ethanol to speed up the reaction and shorten the completion time. The reducing agent is used in excess to ensure that the carbonyl group is completely reduced. Sodium borohydride is fairly soluble in organic solvents. For this reason, the reaction is carried out in an aqueous ethanolic solution. The experiment takes note of the time used for the reaction. The duration of the reaction is done by monitoring the starting materials amounts that remain in the reaction using a thin layer chromatography. The reaction is complete when there is no starting materials remain and working up should be done. Reaction monitoring using Thin Layer Chromatography (TLC) is done by directly spotting tiny reaction mixture amounts onto the TLC plates. The spotting is done at regular intervals and checking how much starting materials remain by running the plates using Hydrochloric Acid. Small samples are withdrawn and each sample is worked up instead. The working up is equally done to the final reaction mixture to end up with the product. The organic compounds solutions are obtained and analyzed by Thin Layer Chromatography (TLC).   The product isolation is achieved though filtration after doing a work up. The product is then crystallized to purify. Milimolar scales are used in the reaction, which require special care to avoid or minimize mechanical losses, which can be substantial. Weighing is done using analytical balances.