SN2 post lab

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Virginia Commonwealth University *

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CHEZ-301

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Chemistry

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Jan 9, 2024

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docx

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SN2 Post Lab Suzanne Varughese CHEM 301, L16 1. This synthesis is an example of an Sn2 mechanism. What are the hallmarks of Sn2 compared to Sn1? First the procedure of Sn2 compared to Sn1 is completely different. For Sn2 we had to perform reflux and distillation for the solution, unlike Sn1 in which we performed different small reactions. Another hallmark is that Sn2 reactions are favored with primary carbon substrates. 1-butanol is a primary alcohol in our experiment, unlike Sn1 mechanism that uses a tertiary carbon substrate. 2. Write a formal procedure for this experiment. Use the modifications that were made in lab (ie base it on the procedure you actually did in lab). 6.2 mL of 1-butanol was placed into a 100 mL round bottom flask. Subsequently, 10 mL of 48% hydrobromic acid (HBr) was added to the flask while swirling. A cautious and slow addition of 4 mL of concentrated sulfuric acid (H2SO4) to the flask was performed with swirling. In case the flask became excessively hot, it was cooled in an ice bath. A stir bar was added to the flask, and a reflux condenser was connected to the top of the round bottom flask. The water hoses were connected to the condenser, with water entering through the bottom nozzle and exiting through the top nozzle. Once the apparatus was connected, the reaction mixture was heated at reflux for 30 minutes. Subsequently, the flask and its contents were allowed to cool to nearly room temperature using an ice bath. 10 mL of de-ionized water was slowly, carefully, and with swirling, added to the mixture through the condenser. The apparatus was converted to a simple distillation. The contents of the flask were distilled into a 25 mL round bottom flask immersed in an ice bath. Distillation was stopped when the temperature of the distillate reached 96C, due to it being distilled for 20+ min. The aqueous layer was removed from the distillate using a transfer pipet. Then, 5 mL of de-ionized water was added to the organic layer of the distillate, mixed well with the transfer pipet. The aqueous layer was separated from the organic layer. The aqueous layer was combined with the original aqueous layer. The organic layer was washed with 5 mL of 5% sodium bicarbonate solution, and the layers were separated, combining the aqueous layers in a "waste flask." The organic layer was washed once more with 5
mL of de-ionized water, separating the layers, and combining the aqueous layer with the other aqueous washes. The organic layer was dried over anhydrous sodium sulfate. The dry organic layer was decanted or pipetted into a clean, dry, 44.12 g round bottom flask. The product was weighed at 1.199 g, and an IR spectrum was run on the product. 3. Calculate theoretical yield of 1-bromobutane using 1-butanol as the limiting reagent. 4. Calculate the percent yield of 1-bromobutane.
5. Attach your IR and identify the peaks that belong to 1-bromobutane and what bonds they correspond to. A strong peak between 2850-3000 cm -1 would be the peaks that belong to 1- bromobutane, because that’s where an alkane (C-H stretch) strength is shown. 6. Explain the difference in IR between 1-bromobutane and 1-butanol Unlike 1-bromobutane, 1-butanol has an -OH group attached to the compound. The IR spectrum in 1-butanol would show sharp/broad around 3200-3650 cm -1 . Another difference would be 1-bromobutane would show strong, sharp peaks around the 300-500cm -1 region because of the C-Br bond stretch. 7. Based on your IR, do you think 100% of the water was removed from the organic layer? Why/why not? Based on the IR graph, I believe that around 100% of the water was removed from the organic layer. In an IR spectrum graph, O-H stretching in the range of 3200-3650 cm -1 would indicate the presence of H 2 O. In this graph, I can see that there is no strong, sharp peak around this range. This indicates that there is lack of water present in the organic layer that ran through the IR spectrum.
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