Orgo Lab - Benzoin Experiment Discussion Part 4 PP

1,2-diphenylethane-1,2-diol was present and relatively pure in the final product. Yet the percent yield was 14%. This is a lower % yield than expected. This may be a result of impurities due to the incompletion of the reaction, loss of product in transfers, or evaporation. These mistakes could have been avoided if extra time was given to allow the reaction to complete and as few of transfers between glassware were performed as possible. Another possible change that may increase the % yield would be to increase the moles of benzoin in the reagents. Due to the fact that one mole of benzoin reacts with one mole of sodium borohydride and there is 0.2 mmol less of benzoin than sodium borohydride in the reaction, benzoin is the limiting reagent. By increasing the molar amount of benzoin in the reaction, the reaction would produce a larger amount of product yield, ultimately increasing the % yield.