post lab report 4 ochem

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Dec 6, 2023

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Joylin Romero Andrew Isho Chem 2125-11353 Post laboratory: Williamson Ether Synthesis Calculations: Theoretical amount 1.5g p -acetamidophenol x (1mol/151.17g) x (1mol phenacetin/1 mol of p ) x (179g/ 1 mol) = 1.78g Percent Yield : (actual/theoretical) x 100% (0.776g / 1.78g) x 100% = 43.6% Percent Recovery: (final product/ initial product) x 100 (0.776g/ 1.5g) x 100% = 51.7% Results and Discussion: After just a couple of minutes into the reflex I notice an initial color change from clear to a light pink. After 45 minutes of refluxing and the addition of DI water I observed a second color change this time from light pink to light green which can be seen in figure 1. This change of color can be caused from a couple of distinct reasons, one being the order of addition of each reagent and second if excess amount of bromine is added. My percent yield was only 43.6 %, a low percent yield can indicate that there was not an equal amount of moles of methoxide ion and p-actemaidophenol. In fact, a low yield can mean there were excess moles of methoxide ion and excess moles of methoxide ion makes it a competing nucleophile. My percent recovery indicated that only about 50% of my product was recovered. Reasons for the loss of some of my product could be not fully getting all the crystals from the beaker and excess amount of ethanol used during the purification process. The melting point range for my product was between 132 ℃ and 133.3 ℃ which is close to the melting point range for phenacetin which is between 134 ℃ and 136℃. When looking at the IR spectroscopy (figure 2), we see a medium stretch around 3257 cm-1 which indicates an amine group is present as well when you look at the fingerprint region, we see a sharp and strong peak at around 1300 cm-1 and this indicates an ether functional group is present in my product. Looking at the proton NMR we see two doublets between 7 and 8 ppm which represents a benzene ring as well at around 4.0 ppm we have a quartet which means we have three protons neighboring each other (CH3) but also having peaks between 3.3-4 ppm also indicates an ether is present. After getting the melting point of my product and analyzing the IR and NMR it can be concluded that the Williamson ether synthesis reaction was effective in forming an ether from our base reagent p -acetamidolphenol. Conclusion: To conclude, the Williamson ether synthesis experiment was used to form an ether functional group in phenacetin. This experiment was useful in understanding the mechanism behind the

reaction; how an alkyl halide reacts with its conjugate base to form the ether. Overall, this was an interesting experiment being able to see how the addition of DI water to bromoethane solution led to distinct color changes. Post Lab Questions: 4) - C-O-C: 1244 and 1047 cm^-1 - C=O: 1653 cm^-1 - para disubstituted benzene: 837 cm^-1 - N-H: 3300 cm^-1 5) Para disubstituted benzenes follow an AB pattern which means it has two doublet signals and this is due to its plane of symmetry. The protons of one side of the benzene ring have the same electronic environment which represents one peak and since there are two protons, they split each other's signal in doublet similarly goes for the protons on the other side of the benzene.

Figure 1: Color change after DI water was added

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