Experiment 7 Lab Report PDF

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Complete lab report for exp. 7...

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Mikayla Hyde CHEM 2221L June 30, 2020 Column Chromatography Introduction The purpose of this experiment was to take a mixture of three compounds – acetylferrocene, ferrocene, and 9-fluorenone – and isolate these compounds from one another using column chromatography and thin-layer chromatography analysis. The differences in polarity between these three compounds were what allowed the column chromatography technique to effectively separate them. A nonpolar solvent was first run through the column, extracting the most nonpolar compound: ferrocene. Then a more polar solvent was run through the column, followed by an even more polar solvent, thereby extracting the other two compounds in a predictable order. Thin-layer chromatography analysis was then employed to determine which of the 5-mL vials of solution contained the pure chemicals. Results/Calculations Recovered Mass (g)

% Composition

Rf Value

Ferrocene

0.027 g

30.68%

0.74

9-Fluorenone

0.028 g

31.82%

0.43

Acetylferrocene

0.033 g

37.50%

0.12

● Total recovered mass: 0.088 g ● Total percent recovery: 78.57% Sample Calculations: ● ●

Recovered mass of component (in g) • T otal recovered mass (in g ) 0.027 g ○ % Composition of F errocene = 0.088 • 100 g Distance travelled by the compound (in mm) value = Distance travelled by the solvent front (in mm) 36 mm = ○ R f V alue of F errocene = 48.5 0.74 mm

P ercent Composition =

Rf

100 = 30.68%

Answers to Questions 1) Petroleum ether is a nonpolar solvent, so if the column had been eluted with only this compound, then it is likely that only the ferrocene and 9-fluorenone would have been displaced from the stationary phase because nonpolar solvents can only elute nonpolar compounds. And while the ferrocene would respond very well to the nonpolar solvent, the 9-fluorenone would only respond partially as well, with some of the compound likely remaining in the stationary phase. The acetylferrocene, a polar compound, would remain in the stationary phase and not elute at all. 2) tBME is a more polar solvent, so if the column was eluted with only this compound, then all three of the compounds in the mixture – both polar and nonpolar – would be easily eluted. However, if the solvent was too polar, then all of the components of the solution would elute quickly and all mixed together, rendering the process wholly ineffective. 3) Based on our results, the “waste” acetylferrocene bottle appears to be about a third of each of the three compounds in the bottle. Ferrocene made up 30.68% of the bottle, 9-fluorenone 31.82%, and acetylferrocene 37.50%. Discussion/Conclusion

Based off of the TLC plate results, it appears that the three compounds in this mixture were isolated from each other very well. A higher Rf value signals a more nonpolar (and less  polar) compound and the calculated Rf values clearly correspond with our knowledge about order of increasing polarity in the compounds. The use of a nonpolar and then a more polar solvent in the column chromatography also corroborates this conclusion. The ferrocene traveled the farthest on the TLC plate (also meaning it had the highest Rf value) and was also the first compound to be eluted by the nonpolar solvent, making this the most nonpolar compound in the mixture. The 9-fluorenone was next, traveling about half the distance on the TLC plate that the ferrocene did and being eluted by a mixture of the nonpolar and polar solvent, leading to the conclusion that the 9-fluorenone has some polar and some nonpolar character. Lastly, the acetylferrocene was eluted by an entirely polar solvent and traveled only a very short distance on the TLC plate, signifying it as a very polar compound. Overall, the three compounds appear to have been isolated from one another successfully....