TLC analysis

You are now ready to develop and visualize your TLC plates from the reaction.

The plates will not only help you discern the relative polarity of your starting material and product(s), they will also help you determine the rate at which the reaction occurred.

Developed and visualized TLC plates for all of the possible starting material/solvent combinations are shown below. All plates were developed using 60:40 hexane:ethyl acetate as the solvent system.

benzil in isopropanol
(UV light)

The photo shows two thin layer chromatography plates glowing green under UV light. Each plate has three lanes, labeled from left to right: 10, 12, 15, 0, 2, and 5. A small ruler is superimposed on the left side of the image, with its 1.5 cm marking aligned with the spotting line of the plates. In the 0 lane, we see a large horizontal smudge around the 6.5 cm marking. In the 2 lane, there is a clear spot on the spotting line, followed by a long streak extending from the 2.4 cm marking to the 4.7 cm marking. Then, one clear spot centered around 5.6 cm and a smaller spot around the 6.4 cm marking. The 5 lane looks very similar to the 2 lane, but the long streak starts at the spotting line, rather than the 2.4 cm marking. The 10 lane looks very similar to the 5 lane, but the final spot around the 6.4 cm marking has faded to the point of being almost invisible. The 12 lane looks very similar to the 10 lane, but with the final 6.4 cm spot even smaller and more faded. Finally, the 15 lane has a small spot at the spotting line, a line streak extending from 2.4 cm to 4.7 cm, and then an even thinner streak extending from 4.7 cm to 5.6 cm.

benzil in isopropanol
(iodine)

The photo shows two thin layer chromatography plates. All of the smudges, spots, and streaks described in the UV visualized photograph have been outlined in pencil in this photo. The spots on the spotting line in lanes 2, 5, 10, 12, and 15 are all stained dark brown in this image. The smudge in lane 0 and the longer streaks in lanes 2, 5, 10, 12, and 15 are all stained light brown in this image. The higher up spots in lanes 2, 5, 10, 12, and 15 are all colorless in this image.

benzil in ethanol
(UV light)

The photo shows two thin layer chromatography plates glowing green under UV light. Each plate has three lanes, labeled from left to right: 0, 2, 5, 10, 12, and 15. A small ruler is superimposed on the left side of the image, with its 1.4 cm marking aligned with the spotting line of the plates. In the 0 lane, we see a single, dark spot centered even with the 6.8 cm marking on the ruler. In the 2 lane, we see a spot at the spotting line, followed by a long streak extending from the 2.4 cm marking to the 4.6 cm marking. Then, there are two small, faint spots centered at 5.6 cm and 6.8 cm, respectively. The remaining 5, 10, 12 and 15 lanes all have the same features as the 2 lane, although the streaks in the 10, 12, and 15 lane lean increasing to the left, indicating that the mobile phase did not necessarily climb the plate via a strictly vertical path.

benzil in ethanol
(iodine)

The photo shows two thin layer chromatography plates. All of the spots and streaks described in the UV visualized photograph have been outlined in pencil in this photo. The spots on the spotting line in lanes 2, 5, 10, 12, and 15 are all stained dark brown in this image. The longer streaks in lanes 2, 5, 10, 12, and 15 are all stained light brown in this image. The higher up spots in lanes 0, 2, 5, 10, 12, and 15 are all colorless in this image.

benzil in methanol
(UV light)

benzil in methanol
(iodine)

benzoin in isopropanol
(UV light)

benzoin in isopropanol
(iodine)

Onward to purification!

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