O-Xylene → Pyridine, 2,3,5-trichloro-

Participants

Reaction Conditions

Reaction Steps

A 3000 mL, four neck round bottom flask was equipped with a mechanical stirrer, thermometer, reflux condenser, and an opening for the addition of zinc dust. The flask was charged with ortho-xylene (630.4 g, 725 mL) followed by the addition of 2,3,5,6-tetrachloropyridine (525 g, 2.42 mole). Agitation was started and water (775.1 g, 775 mL), 50% NaOH (1162.7 g, 765 mL), and 25% tetramethylammonium hydroxide (5.2 g) were added to the flask. The reaction mixture was heated to 50° C. and zinc dust (195.0 g, 2.98 mole) was added, in equal portions, over a 5-hour period while holding the temperature between 55-60° C. The reaction mixture was then heated at 55-60° C. for an additional 5 hours. After the reaction, the layers were allowed to separate and the top layer (organics) was filtered. Hydrochloric acid (32%, 750.2 g) was added to the bottom layer which was then heated under reflux for 5 hours to convert unreacted zinc to zinc hydroxide (the zinc hydroxide can subsequently be isolated by filtration for recycle value). Organics present in the bottom layer were removed by steam distillation during this time using a Dean-Stark trap, and added to the organics layer. Fractional distillation of the organics layer gave an isolated yield of 2,3,5-trichloropyridine of 65%.

Provenance & Evidence