CHEM 2204 Chromatography Lab

Topics: Thin layer chromatography, Chromatography, Solvent Pages: 5 (1263 words) Published: January 13, 2015
CHEM 2204 Chromatography Lab
by wyk.wong » Fri Jul 11, 2014 10:25 am
Results and Calculations
Rf values
Rf=(Distance moved by the spot (cm))/(Distance moved by the solvent front (cm))

Toluene:
Rf=2 cm/3.8 cm=0.53 (Fluorenone)
Rf=1.1 cm/3.8 cm=0.29 (Fluorene)

Hexane:
Rf=1.8 cm/2.2 cm=0.82 (Fluorene)
Rf=0 cm/2.2 cm=0 (Fluorene

Table 1: Experimental IR peaks compared to literature IR peaks for fluorenone

Functional group

Experimental peak (cm-1)

Literature peak (cm-1)

C-H

3010.5

3013

C=O

1715.2

1715

C=C

1599.6

1600

Table 2: Experimental IR peaks compared to literature IR peaks for fluorene

Functional group
Experimental peak (cm−1)
Literature peak (cm−1)
C-H
2956
Not present
C=C
1477
Not present

Discussion
As indicated by the diagrams above, both TLC plate tests went as expected and showed that the separation went very well. For the TLC plate in toluene, both the fluorene and fluorenone shifted, but the fluorenone shifted farther. This is expected since the polarity of toluene and fluorenone are more similar. However, since fluorene shifted to some degree as well, this indicates that fluorene is slightly soluble in toluene. Since the Rf values are 0.53 for fluorenone and 0.29, the test went as expected since fluorenone is more soluble in toluene. For the TLC plate in hexane, the fluorene moved up while the fluorenone stayed on the line, which was expected. The Rf values were 0.82 for fluorene and 0 for fluorenone. Overall the purpose was fulfilled as the TLC plates indicate that the two substances were separated well and also the IR spectra indicate that the experimental IR is very similar to the literature value.

An IR spectra was obtained for fluorene. Unfortunately, the experimental IR spectra did not even remotely match the IR spectra from the literature values. For instance, in the literature IR, a peak at 2956 cm−1 and 1477 cm−1 represent the C-H and C=C bond, respectively. These peaks are not present on the experimental IR. Also, the fingerprint regions do not match either. Therefore, an error must have occurred. Either the fluorene was not pure enough or there was an error in the IR process. The TLC plate indicated that the separation proceeded as expected, so it is unlikely that the fluorene is that impure that it does not slightly resemble the literature IR. So either something went wrong in the IR process or the reader was not functioning properly. Since the IR for the fluorenone seemed fine, the most likely possibility is that collecting the sample for the IR was not done properly. One possibility is that not enough sample was placed on the salt plate. Another likely possibility is that the fluorene was contaminated with another substance or the salt plate was not cleaned well enough.

An IR spectra was also obtained for fluorenone.Once again, the different peaks on the IR spectra represent the different functional groups. The first peak on the experimental spectra is at 3010.5 cm-1,while the corresponding peak on the literature value is 3013 cm-1. Both these peaks indicate that aromatic carbon-hydrogen bonds are present. Another major peak for fluorenone that represents a functional group is the peak at 1715.2 cm-1 for the experimental IR, and 1715 cm-1 for the literature IR. This corresponds to the carbon-oxygen double bond that is the ketone of fluorenone. The last peak to represent a functional group in fluorenone is the peak at 1599.6 cm-1 for the experimental IR and 1600 cm-1 for the literature IR. This represents the carbon-carbon double bond of fluorenone. Overall the fingerprint region (1600 cm-1 – 400 cm-1) matches the literature value very closely. Therefore, the fluorenone that was obtained can be considered very pure and this is verified even further by the TLC plate test. The experimental technique employed for this experiment was bench-top chromatography to separate the fluorene and fluorenone. For...

References: http://sdbs.db.aist.go.jp (National Institute of Advanced Industrial Science and Technology) July 9th, 2014
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