Column Chromatography Lab Report

The purpose of this lab was to synthesize 2-nitrophenol and 4-nitrophenol from phenol, sodium nitrate, and sodium nitrite, as well as to use column chromatography to isolate the two products from one another and the byproduct 1,4-benzoquinone. The reaction was monitored by Thin Layer Chromatography to track the progress if the refluxed reaction. Column chromatography was used as a very effective technique for separation as both solids and liquids can be separated by column chromatography. The two nitro phenol products were compared using melting point determinations and the products were also classified and checked for impurities by determination of IR and 1H NMR spectra.

Results and Discussion Column chromatography is the most useful purification

The nitro group attacks either the ortho or the para position of the phenol, due to a resonance form that puts the negative charge on either of these two carbons on the ring. This reaction competes with a side reaction that forms the 1,4-benzoquinone byproduct when the phenol is oxidized by the nitric acid. Therefore, through these reactions the three different products were formed. The reaction was monitored using Thin Layer Chromatography and the products could be clearly seen separate from the original phenol structure. The 4-nitrophenol moved the least on the TLC plates followed by the phenol, 1.4-benzoquinone, and the 2-nitrophenol move the most with the mobile phase due to hydrogen bonding within itself not allowing it to bond with silica very well. Once the phenol disappeared in the TLC product lane and became fainter in the co-spot lane it became clear that the reaction was at completion. The reaction mixture was then purified using column

The expected melting points for 2-nitrophenol and 4-nitrophenol were 45°C and 113°C respectively and the observed melting point temperatures were 45-46.1°C and 112-114°C respectively. From the melting point it is observed that the melting points indeed match but further analysis can be taken to ensure pure product. From the IR and 1H NMR spectra we can confirm the products produced are indeed the ones intended to be made. From the IR spectra for 2-nitrophenol predicted peak values are met at 3300-3000 cm-1 (3237.56, 3113.87, and 2961.95 cm-1) for the C-H aromatic region of the product. The aromatic nitro group region around 1350 cm-1 was also observed at 1365.90 cm-1. Other expected peaks at 1583.02 cm-1 (aromatic C-C) and 1016.21 cm-1 (C-O alcohol) are also seen and there are no outlying peaks that would suggest other products as well. From the 1H NMR spectra for 2-nitrophenol, a very similar result is observed. We see multiple peaks in the 8.0-6.5 PPM region suggesting the aromatic ring and the correct 8.2 (d, 0.80 H), 7.6 (dd, 0.78 H), and 7.1 (m, 2.00 H) peaks for the ortho substituted product. We also see a very strong outlying peak at 10.6 (s, 0.87 H) representing the alcohol hydrogen in the nitrophenol along with no other strong outlying peaks except for the 2.1 PPM acetone peak. When looking at the