Transcription
Welcome back, everyone. Today we are going to make phosphorus pentachloride, which is another stepping stone in the synthesis of TCPO, also known as an active ingredient in glow sticks. Now that you've seen the warning, let's dive right into it. For this preparation, 85 milliliters of 37% hydrochloric acid, 10 milliliters of distilled water, 10.3 grams of red phosphorus, and 68.5 grams of TCCA were used.
Because this preparation is dangerous, a lab coat, a gas mask, and nitrile gloves should be worn. Because of its danger, we are also conducting this experiment in a very well-ventilated area. As the red phosphorus is the core mist of all the reagents needed, I began by weighing out the phosphorus and adding it to one of those borosilicate burning tubes. If I ever repeated this preparation, I would either use an even bigger excess of chlorine or less red phosphorus, because the phosphorus ended up not fully reacting.
We continued by messing up our totally clean scale while weighing out the TCCA. Now that we weighed out the reagents, we were ready to set up the apparatus. On the left, you see the chlorine generator; on the right, we connected the phosphorus-containing tube to a two-neck round bottom flask; and in the middle, we set up an anhydrous calcium chloride-containing washing bottle. The chlorine is generated over here; afterwards, it's passed through the anhydrous calcium chloride because we obviously want dry chlorine, because wet chlorine would actually react with the phosphorus pentachloride; and afterwards, it's passed over the phosphorus. The final product should end up over here to be collected. All toxic leftover fumes are led into this canister containing water.
A slow addition of hydrochloric acid was started, and with slow, I don't mean what I did right here. Soon after we continued the addition a little more gently. It took quite a while, but just a few seconds later, the apparatus was filled with a nice stream of spicy air. I tried to get the reaction going by using a heat gun. Unfortunately, we ended up having to use the heat gun throughout the entire preparation. Only a few seconds after it started generating this beautiful white smoke of phosphorus pentachloride, it looked like it was passivating. Phosphorus pentachloride starts sublimating at 167 degrees Celsius, and I guess it was just too cold and it stayed on the surface of the phosphorus. If the red phosphorus actually started burning, it would be a whole different story, but unfortunately, it seems to be too unreactive for this preparation, or my stream of chlorine was too slow. Anyways, the phosphorus pentachloride passivated the red phosphorus, and we are to get rid of that phosphorus pentachloride layer. Phosphorus pentachloride sublimates at 167 degrees Celsius. We made it sublimate with the heat gun. You can have a closer look at that phosphorus pentachloride. A lot of it settled in this 90-degree bend. Pure phosphorus pentachloride has a white color; if it's impure, it might be slightly yellow.
It's a pretty straightforward reaction. At first, the TCCA reacts with the hydrochloric acid to form cyanuric acid and chlorine gas. The phosphorus afterwards reacts with the chlorine to form phosphorus pentachloride. Phosphorus trichloride also exists, but we had a huge excess of chlorine gas, and phosphorus trichloride, well, it isn't favored during this reaction. This reaction tends to produce only phosphorus pentachloride, even if we use less chlorine. This is phosphorus pentachloride sublimating. At first, it sublimates straight from the wall because you don't see it melting at first, and afterwards the rest just falls off. We want all of the phosphorus pentachloride to go over into the receiving flask, so we switched off the chlorine generator. It was still producing some chlorine, and afterwards we used the heat gun to sublimate it and to make it go over into the flask. The heat gun turned off after some time due to some temperature control thing, so I first used a small Bunsen burner and afterwards a big Bunsen burner to sublimate the phosphorus pentachloride. With excess phosphorus, phosphorus pentachloride can actually react to form phosphorus trichloride. We, however, had the benefit of still having some chlorine generation, which prevented this from happening. The amount of phosphorus pentachloride that's still left in the tube should be really small, so I just disassembled the apparatus.
What surprised me was the calm nature of the phosphorus pentachloride that was still in this hose adapter thing. I expected it to fume in air like silicon tetrachloride, but this wasn't the case, and fumes were only produced when I dumped it into some water. With water, all the phosphoric acid and HCl are formed. This reaction is exothermic and generates a lot of heat, and some hydrogen chloride might escape as gas. A few sources told me that it can react with water explosively, but I had to neutralize it somehow, and I ended up dumping the apparatus into some water pretty slowly. Every now and again, it fizzed profusely and released hydrogen chloride gas. Because I didn't want to inhale any of that, the gas mask was still worn. Some of the phosphorus-water mixture from the tube was transferred to a can afterwards, and I might recover the phosphorus from it. We ended up transferring some of the phosphorus pentachloride to a vial, which is for my compound collection. Most of it stayed in the round bottom flask, which will be used for making oxalyl chloride, and some of it was transferred to this bottle.
Here's a few facts about my TCPO preparation: We already made phenol from salicylic acid by thermal decarboxylation, and today we made phosphorus pentachloride by chlorinating phosphorus. The next step is to chlorinate oxalic acid to form oxalyl chloride and later on to chlorinate some phenol to make trichlorophenol. Lastly, we are going to react both of them to make the TCPO. Because we already got some phosphorus pentachloride inside of a flask, the oxalyl chloride is going to be the next step. Besides oxalyl chloride, we are also going to make thionyl chloride in a collaboration with Lab Coats. I highly recommend that you check out this channel because they've got a lot of great stuff. If you liked today's video, make sure to like and subscribe, and if you want me to get a better camera and computer for editing these videos, make sure to check out my Patreon. Anyways, I'm wishing you a great day. See you soon.