[music] TLC, or thin layer chromatography, is used as a qualitative tool for either monitoring a reaction or following a column chromatography. The equipment you need is a developing chamber. What I have here is a beaker and a watch glass. To prepare the developing chamber, we want to fill it with 3 or 4 milliliters of the solvent that we've chosen to run the TLC, or what's called the eluding solvent or the developing solvent. I'm going to place a small piece of filter paper in my developing chamber, that I've trimmed, before I start to allow the solvent to rise up the filter paper. This will give a total atmosphere of the solvent mixture in the developing chamber. The next thing we want to do is to spot our TLC plate. So the TLC plate will be given to you in lab. You want to choose an end, so look carefully at the TLC plate and choose an end that's not chipped. The one that's most uniform. After you've chosen a TLC plate, and the end you want to use, you want to use a pencil and place a starting line on the TLC plate. So really lightly with a ruler you might mark. You want to make sure again, above where the solvent is going to be. Just to lightly, really careful not to chip my TLC plate, lightly draw a line with pencil on the TLC plate. You do not want to use pen or ink, because that will dissolve in the organic solvent. Okay, I'm now ready to spot. I'm going to make a little mark, and I'm going to pretend I'm doing a reaction and identify this as starting material and another as product. So you've already pulled the capillaries. Isn't that fun? I love pulling capillaries. You've dissolved a small amount of the starting material in solvent, as well as the product from the reaction in a solvent. Now we want to spot it on the plate. So you draw up a small amount of the sample. Place it on the dot that you've made. And you can see that the solvent spreads out. You just want to dab lightly to add the spot. Sometimes it helps to blow a little to remove the solvent. To check that you actually have spotted enough material, or that you haven't spotted way too much, you could place it under the UV lamp. You should be able to see a nice, small, round spot on the appropriate place. I'm now going to spot the product... on the plate. Again, I would take it over to the UV lamp and check that I have enough sample or the right amount of sample on the plate. Looks great! Alright, now for developing the TLC plate. Be very careful when you're handling the plate, only to touch the edges. You don't want to get your fingerprints on the silica gel, which is very polar, because you'll see your finger marks on there and it will disrupt the eluding materials on the plate. So very gently place it in the solvent slowly. I'm going to make sure it doesn't go... The solvent doesn't go above the spot and let it elute. You want to let the TLC run until it's about a centimeter from the top of the plate. Alright, the solvent's reached a good height on the TLC plate, so you gently remove it. You can still see the solvent on it. And before the solvent evaporates, you want to mark the solvent front, which is how high the solvent went on the plate. This will be very important for calculating the RF value, which is the ratio between the distance the spot moved from the baseline, versus how far the solvent moved from the baseline. Alrght, now the exciting moment has come, where we're going to look at our TLC plate first under the UV lamp, and then we'll put it in the iodine chamber. You want to do the UV lamp first so that the reaction of the iodine with the spots doesn't interfere with the UV visualization. So I'm going to put this under the UV light. (gasps) Perfect. Then circle each spot. So here you can see the starting material has a higher RF value than the product. This is pretty good distance, or I've chosen a pretty good solvent system, in that the starting material is in about the midrange of the plate. I could've even used a little more polar solvent to move both spots a little higher. Alright, now I'm going to visualize it with the iodine. The iodine will react with any polar or pi bonds present in the molecule. You can increase the rate of the iodine interaction by putting it on a steam cone and warming up the iodine chamber. Alright, let's take a look. You can see that each of the spots is stained kind of a yellowish, brownish color. You can also see what happens when you get a little fingerprint on the side there. My fingerprints. Again, the RF value would be the measurement for how far - use centimeters - how far each spot moved from the baseline. So this would be 0.9 centimeters to the solvent front, which is 0.8 centimeters. So the product has a lower RF value than the starting material, which indicates that the product is the more polar compound, and adheres to the silica gel stronger. 00:08:13.593,00:00:00.000 [music]