Separation OF Fluorine AND Fluorenone PDF

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SEPARATION OF FLUORINE AND FLUORENONE BY BENCH TOP COLUMN CHROMATOGRAPHY Aira Monique Felix 101105638

Date Performed: January 22, 2020 Date Submitted: January 30, 2020 Lab Period: Thursday, AM Partner: Louis Green TA:

Results and Calculations Note: the glass wool and the layer of sand were not packed into the bottom of the column as what was described in the lab manual since there was already a layer of white, crystalline solid present on the bottom. However, sand was added on the top of the silica gel. Observations Table 1. Qualitative observations of the starting mixtures that were used throughout the experiment. Compound

Key Characteristics

Diethyl ether and hexanes

-

Clear and colourless liquid petroleum-like odour volatile

Fluorene and Fluorenone mixture

-

Solid, chalky, yellow powder

Silica gel

-

White, fine powdery solid Loses colour upon addition to liquid (hexanes)

Sand

-

White-beige, very fine solid, odourless

Toluene

-

Clear and colourless, very pungent odour volatile

Description during the preparation: -

The fluorene-fluorenone solid had a difficulty dissolving in a 1.0 mL of 1;1 hexanes:ether which resulted being stuck onto the sides of the test tube. Thus 1 more drop was added using the Pasteur pipette then followed by 1 drop of ether alone to fully dissolved everything.

-

During the first fraction, the column almost went dry according from the TA; therefore, more hexanes were added quickly.

-

The collection of fractions 1 (fluorene) reached nearly 50 mL and took 45 minutes evaporating in the steam bath. The second fraction however was less than the first fraction (about 30 mL) and took less time evaporating in the steam bath.

IR Results

Figure 1. IR spectra of fluorene.

Figure 1. IR spectra of fluorenone.

Table 2. Experimental peaks of Fluorene compared to the literature IR peaks1 Functional group

Experimental peak (cm-1)

Literature peak (cm--1)

C-H

3061.7-3014

3100-2900

C=C (aromatic ring)

1472.6 and 1452.2

1475 and 1400

Table 3. Experimental peaks of fluorenone compared to literature IR peaks2 Functional group

Experimental peak (cm-1)

Literature peak (cm--1)

C=O (carbonyl - ketone)

3080-2850

3050-2850

C=C (aromatic ring)

1477.7 and 1397.1

1475 and 1400

C-H

1710

1700

TLC Results Hexanes

Toluene Key: Rf = 0.94

Rf = 0.89 Rf = 0.92

Line on top = solvent line Line on bottom = starting line

Rf = 0.40

F1= fluorene fraction

Rf = 0.37

Rf = 0.57

Mixture = fluorene and fluorenone F2= fluorenone fraction

F1

Mixture

F2

F1

Mixture

F2

Figure 3. TLC plates of fluorene and fluorenone separated by chromatography using an eluant of hexanes and toluene.

Sample Calculation

Rf = distance moved by spot (cm) distance moved by solvent (cm )

=

2 cm

Table 4. Quantitative observations of TLC plate eluted in hexanes. Spot

Distance moved by spot (cm)

Distance moved by solvent front (cm)

Rf

Fraction 1

2.0

3.5

0.57

Mixture

1.4

3.5

0.40

Fraction 2

1.3

3.5

0.37

Table 5. Quantitative observations of TLC plate eluted in toluene.

Spot

Distance moved by spot (cm)

Distance moved by solvent front (cm)

Rf

Fraction 1

3.4

3.6

0.94

Mixture

3.2

3.6

0.89

Fraction 2

3.3

3.6

0.92

Discussion Chromatography is a laboratory technique used for the separation of a mixture. It is mostly use for analysis and purification of an organic compound. The mixture is dissolved in a fluid known as the mobile phase, which carries it through a structure holding another material known as stationary phase. Chromatography is possible because of the variations in hydrogen bonding, structure and polarity of the compounds that are being separated6.

This experiment proceeded smoothly due to the fact that the procedure is not difficult to setup. The evidences for the IR spectra for fluorene and fluorenone when compared to the literature peaks appears to indicate a pure fluorene and fluorenone sample which implies that the experiment proceeds effectively. The experimental peak values for each functional group in fluorene were very noticeable since they were very close to the literature peaks. For the fluorene, the C-H and C=C bonds had an experimental peak of 3061.7-3014 cm-1 and 1472.6 & 1452.2 cm1

respectively. The literature peaks for Fluorene’s C-H and C=C bonds were 3100-2900 cm-1 and

1475 & 1400 cm-1. For the fluorenone, the experimental peak for C=O, C=C and C-H are 30802850 cm-1, 1477.7 & 1397.1 cm-1 and 1710 cm-1 respectively. In general, the main peaks in the experimental IR spectra appear to match those of the literature IR spectra of fluorene and fluorenone.

According on the results of the TLC analysis and on the calculated R f values, it appears that the first fraction (fluorene) and the second fraction (fluorenone) are very close to each other. However, if the calculations of their Rf values were taken from the middle or the beginning of the spot, closer to the starting line, it would appear much better that these two fractions contain two different compounds. Although fraction 1 and fraction 2’ spots have very similar distances near the solvent line, the length of the spots and where they started is a more noticeable indication that there is a difference between the two.

As mentioned in the results section before, there was no glass wool was added on the bottom of the column as it was instructed by the TA. This is due to the fact that there was already a white, crystalline substance that would serve as the same purpose in order to prevent fine

particles from passing through the column and allow the flow of contents to proceed smoothly through the column. Hexanes was used to keep the column wet as this helps column loading and prevents cracks in the column which would negatively affect the quality of the separation which could yield an impure substance. Hexane is nonpolar; therefore, the London dispersion forces that its molecules exhibit interacts with other molecules that exhibit the same intermolecular forces. Hexane interacts with the nonpolar fluorene molecules and both substance flow out of the column together. The more polar substance, fluorenone, remains attracted to the polar silica gel molecules (stationary phase) due to the fact that the molecules of both fluorenone and silica gel exhibit a different interaction: dipole-dipole forces, which allows the molecules of fluorenone and silica gel to interact with each other. Instead of adding hexanes alone, the second eluant was a 1:1 mixture of hexanes-diethyl ether. Diethyl ether has an oxygen atom, an electronegative. Since ether is a slightly polar solvent, it would be needed for the second fraction to interact with slightly polar fluorenone molecules; however, the hexane that stays in the eluant is to slow down the process to a rate that would allow for the separation to be highly effective. It is significant that the slightly polar eluant is poured in second because the more polar the molecule, the longer it stays in the column due to its interaction to the polar silica gel.

The TLC plate that was eluted in toluene had longer spots than the ones in hexanes. Toluene has a benzene ring similar to the benzene rings of fluorene and fluorenone. The fact the it is an aromatic compound, toluene dissolves other compounds with benzene rings better than a compound like hexane which doesn’t have a benzene ring3. The increased solubility from the eluant of toluene allows the compounds to climb further and faster up the TLC plate. The sports measurements on the toluene plate were also more difficult to differentiate since both the fraction

1 and fraction 2 appeared to have reached a very similar distance. Since both compounds did not climb as fast in hexanes eluant, it was easier to see a noticeable variation in distance between fraction 1 and fraction 2. On the experimental peak of fluorene in figure 1, there is a narrow peak around 3000 cm-1 that is closely resembles the long and sharp peak on the same side of the IR spectra of hexane. This may suggest that the fluorene sample may have been contaminated with hexane which shows the significance of condensing the solution on the steam bath until it’s fully reduced to a crystal. A way to improve this is for the fluorene sample to remain longer on the steam bath to ensure that all of the hexanes has evaporated.

As the silica gel was added, the particles stuck on the sides of the column very easily; therefore, more hexanes was added to wash the silica gel down the column. It could have been much easier if the column is being tapped, harder enough, while loading as opposed to adding more hexanes which result to a long time draining the hexane out.

Conclusion The main goal of this experiment was to separate mixture of fluorene and fluorenone through the use of bench-top column chromatography technique and to analyze the quality of the separation by method of thin-layer chromatography (TLC) and infrared spectroscopy. The experimental IR peak for fluorene were C-H = 3061.7-3014 cm-1 and C=C = 1472.6 and 1452.2 cm-1. The experimental IR peak for fluorenone were C=O = 3080-2850 cm-1, C=C = 1477.7 and 1397.1 cm-1, and C-H = 1710 cm-1. For the TLC plate of hexane, the calculated R f value are 0.57, 0.40 and 0.37 for fluorene, mixture and fluorenone respectively. On the toluene TLC plate, the

calculated Rf values are0.94, 0.89 and 0.92 for fluorene, mixture and fluorenone respectively. Both the results of the experimental IR spectra of Fluorene and Fluorenone are very close to their literature IR peaks as well as the noticeable differences in Rf values of fraction 1, mixture and fraction 2 on the TLC plates suggest that the separation of fluorene and fluorenone was successful.

REFERENCES 1. SDBSWeb : Fluorene (no. 1721) IR KBr disc; https://sdbs.db.aist.go.jp (National Institute of Advanced Industrial Science and Technology, accessed July 11, 2019).

2. SDBSWeb : Fluorenone (no. 2223) IR KBr disc; https://sdbs.db.aist.go.jp (National Institute of Advanced Industrial Science and Technology, accessed July 11, 2019).

3. Cao et. al. Solvents as Reagents in Organic Synthesis - Reactions and Applications - 2. The Applications of Toluene and Xylenes; Wu, X. Ed.; John Wiley & Sons: Weinham, 2018.

4. SDBSWeb : Hexane (no. 2118) IR liquid film; https://sdbs.db.aist.go.jp (National Institute of Advanced Industrial Science and Technology, accessed July 11, 2019). 5. Poole, C. CHROMATOGRAPHY. Encyclopedia of Separation Science 2000, 40-64....