Nitrophenol Essay

Abstract: Using a micro scale steam distillation we separated ortho and para-nitrophenol from a mixture that was already made. After the para and ortho were separated we measured their melting points and compared it to the literature values for purity. For ortho-nitrophenol we had 60% recovery and for para 160% recovery. Our melting point ranges were ortho: 45-46Â °C and para 64-95Â °C. Introduction:Â  Nitration: In phenols, -OH group strongly activates the ring system. As a result, phenols are susceptible to oxidation in the presence of concentrated nitric acid (HNO3). Thus, nitration of phenols is carried out with dilute nitric acid and results in the formation of o-nitrophenol and p-nitrophenol. The o-nitrophenol is steam volatile and the mixture of o-nitrophenol and p-nitrophenol is separated by steam distillation, in our case using micro scale measurements for safety and time consumption purposes. (Electrophilic aromatic substitution) We used steam distillation because we are distilling under 100Â °C; above 100Â °C is H2O. Looking at the volatility of o-nitrophenol compared to p-nitrophenol, the p-nitrophenol has intermolecular hydrogen bonding and it occurs due to a large number of molecules are associated together. This association in the p-isomer makes it less volatile. However in o-nitrophenol, intramolecular hydrogen bonding occurs and thus, it exists in a monomolecular state making it more volatile. Results/Discussion: Using a sand bath for transferring of heat through the distillation which was sitting on a hot plate. Using a small round bottom flask which was attached to Hickman’s distillation head and then we attached water through the openings. Using 1.00g of the prepared mixture we placed it in the round bottom flask along with 1.00mL of ethanol and then filled it about 2/3 with water. We added a magnetic spin-vane to the flask as well. We collected the yellow waxy ortho-isomer from groove in Hickman’s distillation head using a Pasteur pipette. We made sure that the solids did not accumulate as this would clog the condenser. If it did we would just turn off the cold water momentarily and the hot vapor would melt the solid. The distillation took about 45 minutes and even though this was the specified time period for distilling the mixture, we felt as though much of the ortho-isomer was left in the small round bottom flask along with the para-isomer and the spin valve. In order to characterize the 2- and 4-nitrophenols, we need to determine their melting points. We compared our results to those in the literature. Data:Â  *some ortho solidified in the Pasteur pipette so there might arise a percent error from this as some ortho was left in there. *we assumed that the starting mixture was about 50% each of o- and p-nitrophenol.