The Economic Synthesis of Pentachlorophenol

Pentachlorophenol is synthesized by taking into a 25 ml pear flask, about 0.9 g of distilled phenol in the fresh state, and about 3.6 mg of phenol. The phenol was labeled, and this was moved into the reaction flask utilizing 2 ml diethyl ether to cause the transfer of content. Using a water aspirator, the ether was stripped, and, in a trap, it was condensed and this is placed in a bath containing dry ice-methyl cellosolve. A water-cooled condenser of about 70cm was fitted with the flask along with a stopper and a capillary delivery tube to deliver the chlorine gas. The flask was fixed in an oil bath containing a magnetic stirrer along with a 670-degree Celsius heated temperature. The chlorine gas was later bubbled into phenol that remained melted via the capillary delivery tube. However, it should be delivered at a rate that does not cause the splashing of phenol on the reaction vessel. At this stage, immediately, 0.1g of aluminum chloride that acts as the catalyst is added to the flask. The catalysts react with the phenol and the chlorine gas to generate pentachlorophenol.

Purification
The crude product of the pentachlorophenol should be purified. The above-mentioned mixture was allowed to react with 5% of sodium hydroxide. This solution was later filtered initially with a Whatman filter paper. The filtered products are emptied into a beaker. Then, the filter was washed using distilled water. Precipitation of the pentachlorophenol happens upon the addition of hydrochloric acid to the filtrate that was obtained. Hydrochloric acid should be added till the pH becomes 2. On a hot plate, this mixture was constantly stirred at 90 degrees Celsius. This gives a precipitated product and this was filtered utilizing a Buchner funnel through the suction filtration. This is later washed with distilled water and subjected to air drying. This dry product is moved to the sublimation flask. The sublimation apparatus containing the water aspirator and the dry product functions as a trap dipped in a bath of dry ice methyl cellosolve. This is done to avoid radioactivity from being released into the environment. White crystals were obtained as a result of sublimation that happened with the help of a water aspirator at 150 degrees Celsius.

The purified product must be checked for any impurities. This is done by diluting the pentachlorophenol product with acetone. This was placed on a plate and subjected to autoradiography. The intensity of the impurities was found out in the autoradiography in the form of peaks. The thin layer chromatography was also done to figure out the impurities. The concentration of the impurity is represented in the form of a peak in a chromatogram. If any impurities were found, the solution was again subjected to the second round of sublimation till a pure form of pentachlorophenol was obtained.