The Infrared Spectroscopy (IR) that was created from the product produced two major peaks outside of the fingerprint region. One peak obtained two spikes, one at 2959.90 and the other at 2873.09. This peak resembles the C-H bonding on the product’s structure. The second peak outside of the fingerprint region occurred at 1739.87. This peak resembles the double bond between the carbon and oxygen atom in the product’s structure. Within the fingerprint region, there was one meaningful peak occurring at 1465. This peak resembles the C-C bonding within the product’s structure.
You are here
In this lab, 3-methylbutyl propanoate was synthesized via a reflux of an 3-methyl-1-butanol and propanoic acid. The reflux was performed with the intention to remove the excess water from the solution. The product was weighed 1.12 g and obtained a sweet, banana/pineapple scent. The percent yield was 70.88%. Although this is a relatively high percent yield, it is not 100%. Some reasons as to why the percent yield was not as high as expected could be due to loss of product during transfers between glassware, not allowing the water to completely evaporate in the reflux reaction, or not thoroughly mixing my solutions before and after the reflux reaction. By not allowing the water to fully evaporate or not mixing the solution completely, impurities may have remained in the product, causing a low percent yield.
In this lab, trimyristin was obtained through extraction and recrystallization. Following the outcome of trimyristin, hydrolysis was performed to obtain myristic acid. Two recrystallizations were completed to ensure the purity of the product and compare the products between the two recrystallizations. The amount of crude product that was obtained through extraction was 0.33 grams and resulted in a percent yield of 33%. After the first recrystallization, the amount of product obtained was 0.208 g and resulted in a percent yield of 20.8%. The melting point of the first recrystallized product was 53-54℃. This is a relatively low melting point compared to the melting point of the Trimyristin compound, 56-57℃, due to the impurities that still remain. The impurities may be present because the mixture may not have fully separated before extraction or recrystallization may have not been completed. The amount of product obtained after the second recrystallization is 0.075 g and resulted in a percent yield of 7.5%. The melting point of the second recrystallized product was 57-59℃. This melting point is higher than the melting point of the first recrystallized product because it is purer due to the additional recrystallization. The amount of myristic acid obtained after hydrolysis was 0.07 g and resulted in a percent yield of 38.88%. The melting point of the myristic acid product was 51-52℃. This is a relatively low melting point compared to trymistrin due to the addition of a carboxyl group through hydrolysis and acidification. The percent yields for all products were lower than expected. This could be due to lost product through evaporation when heating or transfers between glassware. An additional cause of low yield could be from over-washing the filtrate with solvent, ultimately losing some product.
The goal of the experiment was to obtain a product of pure cyclohexene. The presence of cyclohexanol in the product may have been due to improper distillation and washing. There may have been too much product left in the flask after distillation or the distillation rate may have been too high. When washing, the solution could have been mixed more thoroughly in order to obtain a pure product. Two chemical tests were performed to display the presence of alkene, or cyclohexene in this case, in the product. The bromine in dichloromethane chemical test resulted in no color change in the cyclohexene product, proving that the alkene functional group was present. The potassium permanganate chemical test resulted in a dark red/brown color with suspension in the cyclohexanol product, also revealing the presence of the alkene functional group. Therefore, distillation and washing was effectively used to synthesize cyclohexane from the dehydration of cyclohexanol.
The IR test revealed that an alcohol group and an alkene group were present in the product. A large, broad alcohol functional group spike at around 3500 was present proving the presence of cyclohexanol in the product. A small, sharp alkene functional group spike at around 3020 was present proving the presence of cyclohexene in the product. The GC test revealed that there were two components present in the product with a ratio of 1:5 based on their areas. This proves that cyclohexanol and cyclohexene were both present in the product. Cyclohexane spiked first in the GC because it has a lower boiling point and obtained a smaller area. This proves it had a smaller abundance in the product. Cyclohexene spiked after cyclohexane because it has a higher boiling point and obtained a larger area. Cyclohexene has a larger spike in the GC test because it was more abundant in the product than cyclohexanol, obtaining the larger area and higher portion of the ratio.
In this lab, the synthesis of cyclohexene was performed through the dehydration of cyclohexanol. This was done through distillation and several washes. IR, GC, and chemical tests were performed to reveal the presences of any functional groups and the number of components in the product. Distillation started at around 64 degrees Celsius. This was unexpected because cyclohexene boiling point is 83 degrees Celsius and cyclohexanol boiling point is 161.8 degrees Celsius. The lower boiling point present in the distillation of cyclohexanol may have been due to the weak hydrogen bonds in the alcohol functional group and water, or the weak alkene bonds. Cyclohexanol and cyclohexene have a 1:1 ratio. The initial amount of cyclohexanol used was 2.0 g and the finished amount of cyclohexene obtained was 0.43 g. This resulted in a percent yield of 21.4 %. This may have been due to loss of product during glassware transitions, potential evaporation, or not leaving enough solution in the flask during distillation.
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.
After recrystallization, TLC tests were run to see if 1,2-diphenylethane-1,2-diol was present in the products. TLC tests are used to determine the number of components in a mixture. The TLC plates tested are displayed in Figure 1. The first TLC plate, on the left of Figure 1, compares the starting material, benzoin, to the crude 1,2-diphenylethane-1,2-diol product. The spot indicating benzoin was larger and had moved across the TLC plate farther, resulting in a larger Rf value, than the spot indicating the crude 1,2-diphenylethane-1,2-diol product. This reveals that benzoin is less polar than 1,2-diphenylethane-1,2-diol. This is due to the carbonyl group that is present in benzoin. 1,2-diphenylethane-1,2-diol obtains an alcohol group in replacement of the carbonyl group on benzoin. This makes the compound more polar and less likely to move across a TLC plate, obtaining a lower Rf value. The second TLC plate, on the right of Figure 1, compares the starting material, benzoin, to the recrystallized 1,2-diphenylethane-1,2-diol product. The spots on the second plate were almost identical to that of the first plate because it is comparing the same compounds. One plate is using crude 1,2-diphenylethane-1,2-diol and the other plate is using purified 1,2-diphenylethane-1,2-diol. Both the crude and recrystallized plates resulted with only one spot in their lane. This confirms that there was only one component in the product, proving that the 1,2-diphenylethane-1,2-diol product was pure.
The crude product was then recrystallized to purify the compound. The recrystallized product of 1,2-diphenylethane-1,2-diol weighed 0.07 g and obtained a melting point of 138-139 ℃. The melting point for the recrystallized product is higher than the melting point of the crude product. This makes sense because the recrystallized product is pure compared to the crude product. Yet, the melting point of the recrystallized product is lower than the melting point of 1,2-diphenylethane-1,2-diol because it still obtains a minimal amount of impurities. The impurities may be due to not allowing the reaction to complete before ice bathing, filtrating, and recrystallizing the product.
In this lab, benzoin (0.5 g), ethanol (4 mL), and sodium borohydride (0.1 g) were reacted at room temperature. This reaction dehydrated benzoin into 1,2-diphenylethane-1,2-diol. The product was recrystallized and tested through thin layer chromatography (TLC) to observe if the product was present. The target product was obtained at 14%.
After the reaction occurred, the crude product obtained, 1,2-diphenylethane-1,2-diol, weighted 0.378 g and had a melting point of 136-138 ℃. This melting point was lower than expected due to the impurities that may be present. The impurities may be present because the reaction was not carried out completely. The incomplete reaction may be a result of potentially adding the sodium borohydride too quickly, not swirling the solution enough, or not allowing the reaction to occur in an adequate amount of time.