CHE_LAB2(TLC)

CHE_LAB2(TLC) - Usage of Thin Layer Chromatography to...

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Usage of Thin Layer Chromatography to Analyze and Identify Compounds Experiment #2
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Purpose Thin Layer Chromatography (TLC) is a useful method used for the separation of compounds. The separation technique is due to interaction between molecules. Depending on the polarity of the compound, it will yield different results enabling chemists to analyze and identify various compounds. Results and Discussion Understanding R f Values The R f value of benzyl alcohol was taken two times with varying TLC plate length. The R f value for the 4.4 cm TLC plate was recorded as 0.4545. The R f value for the 5.2 cm TLC plate was 0.4423. Within experimental error, the results show that R f values are constant for the same compound. For any compound, The R f value will be constant despite any changes in TLC plate length as long as all other chromatography conditions are constant. R f Values and Solvent Polarity TLC plates with approximately the same length were spotted with phenol. The plates were placed into separate developing champers each with a different eluent. Their R f values were taken. The eluents were hexane and ethyl acetate mixtures. For eluents A, B, and C, the R f values were noted as 0.689, 0.200, and 0.348 respectively. Based on these values, it was concluded eluent B was the least polar, and eluent A was most polar. Eluent B likely was mostly composed of hexane while A was composed mostly of ethyl acetate. The structure of phenol is shown on the right. The Plate Length (cm) R f value 5.2 0.4545 4.4 0.4423 Table 1 Eluent R f value A 0.689 B 0.2 C 0.348 Table 2 O H H H H H H phenol
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addition of the hydroxyl group to the benzene ring creates polarity in the structure. Therefore, phenol binds well to the polar stationary phase. Phenol will require a strong polar solvent in order to “pull it off” the stationary phase. Greater polarity of the solvent or mobile phase implies a greater the migration of phenol. As a result, R
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This note was uploaded on 05/25/2008 for the course CHE 276 taught by Professor Totah during the Fall '07 term at Syracuse.

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CHE_LAB2(TLC) - Usage of Thin Layer Chromatography to...

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