Hydrochloric Acid → Phthalonitrile

Participants

Reaction Conditions

Reaction Steps

To a 2000 mL, three-necked flask fitted with a thermometer, a Dean-Stark trap with condenser, and a nitrogen inlet were added resorcinol (26.0 g, 236 mmol), 4,4′-dichlorobenzophenone (22.8 g, 90.7 mmol), powdered anhydrous K2CO3 (48.9 g, 354 mmol), toluene (25 mL), and dimethylsulfoxide (DMSO) (500 mL). Toluene was used to control the refluxing azeotropic removal of water and to control the temperature of the reaction content. The resulting mixture was degassed with nitrogen at ambient temperature and the Dean-Stark trap was filled with toluene. The mixture was refluxed at 170-180° C. under a nitrogen atmosphere for 6 h or until no more water was observed being collected in the Dean-Stark trap. The toluene was then slowly distilled off causing the temperature to rise in the reaction vessel to enhance the yield of the intermediate hydroxyl salt and high conversion to this intermediate. The reaction mixture was heated above 180° C. for an additional 12 h with a very small amount of toluene present to control the temperature, to totally remove the water, formed as a by-product, so that the reaction could be pushed to completion and high conversion to the hydroxyl salt intermediate. The mixture was cooled to 50° C. At this time, 4-nitrophthalonitrile (52.7 g, 304 mmol) was added in one portion and the reaction mixture was heated at 80° C. for 6-8 h. The mixture was allowed to cool to ambient temperature and poured into a 5% aqueous HCl solution resulting in the formation of a solid. The material was broken up and collected using a Büchner funnel. The white solid was washed with 200 mL of a 5% aqueous KOH solution, with 200 mL portions of distilled water until neutral, with 200 mL of a 5% aqueous HCl solution, and finally with 200 mL portions of water until neutral. The isolated solid was vacuum dried to yield the 2:1 oligomeric phthalonitrile (70.6 g, 90% yield). IR [cm−1]: ν 3072 (C═CH), 2234 (CN), 1586 (C═C), 1478 (aromatic), 1307 (aromatic), 1308 (C—O), 1245 (CH3), 1162 (C—O), 930 (C—O), 847 (aromatic).

Provenance & Evidence