What procedure is used for drying 2,4 dinitrophenol for use in synthesising an ester?
The reaction between thionyl chloride (SOCl2) and oxalic acid creates an acyl chloride intermediate which is very moisture sensitive, so any water in your 2,4-dinitrophenol will deplete one of your key reactants. I would dry the 2,4-dinitrophenol in a vacuum desiccator. To improve the efficiency of the drying process, you could place some phosphorus pentoxide (P2O5) in the desiccator which is a very aggressive drying agent. Thionyl chloride is also very reactive with water, so you should also ensure that there is an excess of thionyl chloride in the reaction mixture to help mop up any stray moisture and improve your yield.
Am I correct in assuming that you are using the SOCl2 to prepare oxalyl chloride, which will then be condensed with 2,4-dinitrophenol to produce bis-2,4-dinitrophenyl oxalate? It’s difficult to predict what effect the adsorbed water will have on your synthesis without knowing what the reaction medium and conditions are. I’m going to assume that you are running the reaction in an anhydrous solvent such as ether or THF with something to suck up the HCl produced by the condensation reaction. If that’s the case, then yes the 35% possible water content (note to other answerer, this does not have anything to do with the solubility of 2,4-dinitrophenol in water…) will interfere quite a bit. At best the H2O is going to react with the acid chloride to hydrolyze it back to the acid plus HCl. So, yeah, you will need to dry it pretty well, and since it is a solid material you will have some difficulty filtering it through sodium sulphate (as a certain chemist of many years has already suggested.
SOCl2 will react with water. The product of the first reaction will also react with the water before it reacts with the phenol. 35% is going to be more moles of water than the 2,3-dinitrophenol so if you used wet phenol you would need a significant excess of the oxalic acid and of the thionyl clhoride. Therefore I would recommend removing the water before adding the phenol to the mixture. A few options: Dissolve the phenol in a solvent and add something that will remove the water (magnesium sulphate). Common lab procedure but not suited for scale up. Put the phenol in an oven and dry it until sufficient water is removed (may not be possible if the water is bound into the crystal structure. There may also be problems handling the dried phenol). Recrystallise the phenol from a solvent so that it forms a solid with less water (more work, but may also purify the phenol before use. I wouldn’t recommend an alcohol as any residual solvent will also interfere with the planned reaction). Dry th
