Which is more reactive PCL3 or PCL5

About the production of phosphorus pentachloride - PCl5

This is my first synthesis which I consider worthy to be published on this platform. Phosphorus pentachloride PCl5is one of the most powerful chlorinating agents that can be used for the production of carbonic acid chlorides. Great care must therefore be taken when handling this very potent chemical. It should also be noted that PCl5smokes in the air because it reacts immediately with the water in the air!

Two neck flask x 2
Dropping funnel
Gas / vacuum adapter
U tube - drying tube
Thermometer adapter / threaded tube
Pasteur pipette
Plastic box
Liebig reflux cooler - better take a more efficient one

hydrochloric acid
TCCA- trichloroisocyanuric acid
Phosphor red
Phosphorus pentachloride

Chlorine is poisonous and gaseous! Only work outside with good ventilation!
Hydrochloric acid is corrosive!
Chloroform vapors have an anesthetic effect! Only work outside with good ventilation!
Red phosphorus is flammable!
Phosphorus pentachloride is extremely reactive and very toxic! Please treat with the utmost respect!
The entire apparatus should be set up beforehand and checked for gas tightness.

Dry at least 100 mL of chloroform using molecular sieves or another suitable desiccant and then distill it off after removing the desiccant.
Set up a chlorine gas generator with the two-necked flask, the dropping funnel and a vacuum adapter. A U drying tube is attached to a tripod. Charge this with calcium chloride to dry gases. The other two-necked flask with a reflux cooler, a thermometer adapter / threaded tube which has a Pasteur pipette attached instead of a thermometer is also built up. A vacuum adapter is also attached to the cooler, which is attached in the middle. Fill a plastic box with a dilute NaOH solution and set it aside. The concentration should be kept low as this box is intended for cleaning the excess chlorine gas and should therefore not become very hot. Now load the dropping funnel on the chlorine gas generator with 150 mL conc hydrochloric acid. The two-necked flask is charged with 100 g of TCCA using a funnel. Close the (pressure equalizing !!!) dropping funnel at the top with a stopper and place it on the two-necked flask. The vacuum adapter is also put on and connected with a hose to the U-tube already charged with CaCl2. The outlet of the U drying tube is connected to the Pasteur pipette with a hose. The two-necked flask, where the main reaction should take place, is charged with 1 g of red phosphorus and 100 mL of the dry chloroform. Then the reflux cooler is put back on. A vacuum adapter is attached to this, which is connected with a hose protruding into the plastic box and into the solution. This is attached to the box with a clothes peg. Turn on the water for the reflux cooler. The dropping funnel is then opened so that one drop of HCl drips onto the TCCA every 3 seconds. The chlorine gas flows through the hoses and the drying tube and becomes drier in the dry chloroform, which contains the red phosphorus. The excess chlorine gas is then introduced into the NaOH solution in order to be rendered harmless. The reaction is very exothermic and you can see that the chloroform is starting to reflux. It is important to ensure that the Pasteur pipette does not stick! The reaction is complete when the chloroform no longer refluxes and all of the red phosphorus turns into a yellowish paste - the PCl5has passed. The tap of the dropping funnel is closed and you wait until EVERYTHING of the chlorine gas still in the apparatus has been introduced into the NaOH solution. It is imperative to ensure that no NaOH solution is sucked back through the hose into the reaction when negative pressure is created. This could have problematic consequences due to the reactivity of water and PCl5 The two-necked flask with the PCl5is taken from the aperature and closed as quickly as possible with two stoppers. Then the chloroform is on an oil bath from the PCl5Distilled to dryness. The obtained PCl5is transferred to a previously weighed GL45 vessel with a PTFE seal. This vessel is then weighed again and properly labeled and stored dry and protected from light.

Yield: 0.0319 mol, 6.65 g (98.9% of theory)

The chloroform used is distilled off again and then with 1% abs. EtOH stabilized and placed in a container labeled "Only for PCl5Production "(due to possible residues) kept separately for reuse.
The pH of the NaOH solution is determined using PH paper and neutralized as well as possible and then disposed of in the drain, since it should only contain NaCl, some unreacted NaOH, HCl and water.
The CaCl used2is disposed of or reused depending on how much the solids clump.
The TCCA-HCl reaction mixture is fed to the aqueous acidic waste.


Phosphorus reacts with five equivalents of chlorine to form phosphorus pentachloride

Note on the choice of solvent:
Among other things, chloroform is one of the solvents that can be used for this reaction, as the carbon is already bound to three chlorine atoms. A better choice would be carbon tetrachloride as it is completely chlorinated. However, carbon tetrachloride is very difficult to obtain despite its many uses. DCM - dichloromethane could also be considered as a possible solvent, but it should be noted that the chlorination of the carbon, which is a side reaction, releases a lot of energy in the form of heat, which could lead to a thermal runway, which could lead to product loss and could pose possible security risks. DCM was also not tested because of these concerns.



I have to apologize very much for not being able to upload pictures, but my cell phone camera is currently splintered. (I dropped my cell phone on the hard concrete floor minutes before entering the laboratory ... You have to be unlucky ...) I tried to draw the aperature for better understanding.

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