The plates were run in a 9: 1 of CH2Cl2: ethanol, which is a moderately polar solvent. The starting material (benzoin) had an Rf value of 0.75 on both plates. The crude Rf (0.44) and recrystallized Rf (0.48) traveled less distance on the plate than benzoin indicating their increased polarity. Hydrobenzoin is less polar than benzoin because secondary alcohols are more polar than ketones. Sodium borohyhdride was selected as the reducing agent in this experiment instead of more explosive lithium aluminum hydride, and it is selective in reducing only aldehydes and ketones. Sodium borohydride was sufficient for fully reducing the benzoin, demonstrated by the lack of observed benzoin in both crude and recrystallized products.
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