Monday, 27 October 2014

Quick Post: Extraction of dichloromethane from paint stripper.


Dichloromethane is a versatile halogenated solvent that will be used in many upcoming syntheses. Dichloromethane is immiscible with water, hence is a useful solvent for performing extractions from reaction mixtures. Further, dichloromethane's low boiling point (40°C) makes it ideal for a home laboratory setting, as a rotovap or similar apparatus is not required for the near complete removal of the solvent from a product. In this experiment, dichloromethane will be obtained from paint stripper via distillation.


To extract dichloromethane from paint stripper via distillation for laboratory use.

Safety and Environment
Gloves, goggles and appropriate ventilation must be present throughout the procedure. Depending on the brand of paint stripper, numerous products could be present. As such, the appropriate safety measure must be undertaken (read the meds sheet). Dichloromethane is a suspect carcinogen and is an inhalation hazard. In addition, dichloromethane is very dangerous for the eyes and is toxic. Familiarise yourself with the meds sheet and prepare accordingly. Do not allow any of the wastes from this procedure to enter the environment, place in appropriate waste container and take to waste disposal facility. To clean up the left over distillate, it may be helpful to use methylated spirits. 


Atop a hotplate,  a 250 ml round bottom flask was filled with ~80 ml paint stripper, along with a 15-20 boiling chips. 
An ice cooled distillation apparatus was set up collecting the fraction from 36-40º which contains primarily dichloromethane and methanol which form an azeotrope at 37.8º C.

 The distillation was shut down after 2 hours which yielded ~30 ml of crude product. The crude product was placed into an 125 ml separator funnel and washed with 2x10 ml ice cold distilled water to remove methanol. Subsequently, the washed product was dried over anhydrous magnesium sulfate, which was then filtered and added to an amber glass bottle. Final yield was 25 ml of dichloromethane.  


The main aim of this procedure was achieved. The DCM was characterised by it boiling point, relevant product composition, and its density (sank in water). The yield was less than 50%, most likely due to small scale; a small amount was lost in the water washings, and inefficient condensing of distillate. Ideally a larger condenser should be implemented, as well as larger scale. This will result in better yields. 

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