Transcription
Welcome back, everyone. Today we are going to make some thionyl chloride. For this, 37.8 grams of sodium sulfide, 25.6 grams of phosphorus pentachloride, and 54 milliliters of 37% hydrochloric acid are needed. PPE: a gas mask, nitrile gloves, and a lab coat should be worn. We are also working in a very well-ventilated environment.
37.8 grams of sodium sulfate and 54 milliliters of 37% hydrochloric acid are used to generate sulfur dioxide. A huge excess of both of these reagents is used to ensure that all of the phosphorus pentachloride reacts. The hydrochloric acid was added to a pressure-equalizing addition funnel. You can have a closer look at the phosphorus pentachloride and still have some for the preparation of oxalyl chloride in the future. Today's apparatus looks like this: on the left we have the sodium sulfate and hydrochloric acid sulfur dioxide generator. The gases afterwards sleds through a washing bottle containing anhydrous calcium chloride and into the phosphorus pentachloride. The resulting thionyl chloride will be distilled using simple distillation.
Before starting the sulfur dioxide generation, we turned up the stirring to the maximum. Now that the stir bar is spinning around, we are ready to start sulfur dioxide generation. Instantly after the hydrochloric acid makes contact with the sodium sulfide, this toxic and colorless gas is generated. You can see the solid phosphorus pentachloride reacting with the sulfur dioxide to form our liquid product. The entire reaction looks like this: at first we generate the sulfur dioxide from sodium sulfide and hydrochloric acid. After drying, the sulfur dioxide reacts with the phosphorus pentachloride to form thionyl chloride and phosphorus oxychloride. We are using two times as much sulfur dioxide as we actually need. The reason for that is simple: a lot of the sulfur dioxide doesn't react and ends up in the gas scrubber. Because everything turned liquid, it seemed like we used enough sulfur dioxide.
The next step is going to be a simple distillation. Before we can begin, however, we have to switch out this hose connector for a glass stopper. I needed to film this: small amounts of liquid when stirred always make these fascinating patterns. It's time to get back to the project. The heating mantle was turned to medium heat. We waited a few minutes and it soon started to boil. Pure thionyl chloride boils at around 76 degrees Celsius, so everything coming over below 90 degrees C was collected and the rest was discarded. Phosphorus oxychloride boils at around 106 degrees Celsius, which means that our thionyl chloride will be a little contaminated with it, but it should be minor. Once the thermometer reached 90 degrees C, we switched out the receiving flasks. I still wanted to collect whatever comes over because even phosphorus oxychloride mixed with thionyl chloride is still a great chlorinating agent.
The product was ampuled, and even the stuff that came over later was also ampuled. I really need to get some new gloves because I ran out of gloves and I had to use these to neutralize the stuff that's left in the apparatus. I decided to add some water. After adding the pipette, you can already see a lot of fumes. The fumes consist of hydrochloric acid, phosphoric acid, and sulfurous acid. To make throwing it away safe enough, everything was neutralized afterwards using some sodium carbonate solution. In the end, we were left with 7.4 grams of thionyl chloride, which should be fairly pure, and this corresponds to yields of around 50.7 percent. Also, we got 11.3 grams of crude contaminated product. The crude stuff definitely contains a lot of phosphoryl chloride and even phosphorus pentachloride, but it should still be good enough to chlorinate a few things.
And there you have it. Now you've seen how to turn phosphorus pentachloride and sulfur dioxide gas into chlorinating agents like thionyl chloride. I haven't planned anything with it yet, so if you have any ideas, let me know and write a comment. If you liked today's video, make sure to drop me a like, and if you don't want to miss out on further chemistry content like that, make sure to subscribe. [Music]