Hydrochloric Acid → Phthalonitrile

Participants

Reaction Conditions

Reaction Steps

To a 250 mL, three-necked flask fitted with a thermometer, a Dean-Stark trap with condenser, and a nitrogen inlet were added 4,4′-biphenol (10.0 g, 53.7 mmol), 4,4′-dibromodiphenylacetylene (8.93 g, 26.6 mmol), (PPh3)3CuBr (0.3 g), powdered anhydrous K2CO3 (11.1 g, 80.6 mmol), toluene (20 mL), and N,N-dimethylformamide (DMF) (100 mL). The resulting mixture was degassed with argon at ambient temperature. The Dean-Stark trap was filled with toluene and 5 mL was added to the reaction. The mixture was refluxed at 135-145° C. to remove the water by-product by azeotropic distillation under an argon atmosphere for 12 to 18 h or until no more water was observed being collected in the Dean-Stark trap. FTIR spectroscopy was used to confirm and monitor the formation of the desired oligomeric product. The toluene was then removed by distillation and the reaction mixture was cooled to 50° C. At this time, 4-nitrophthalonitrile (9.32 g, 53.9 mmol) was added in one portion and the resulting reaction mixture was heated at 80° C. for 6-8 h. The mixture was then allowed to cool to ambient temperature and poured into 500 mL of 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 dissolved in chloroform (200 mL), and washed with 200 mL of a 5% aqueous KOH solution, with 200 mL of distilled water until neutral, with 200 mL of a 5% aqueous HCl solution, and finally with 200 mL of water until neutral. The solvent was removed in vacuo and the solid was vacuum dried to yield the 2:1 oligomeric phthalonitrile (19.2 g, 90% yield). IR [cm−1]: λ3075 (C═CH), 2232 (CN), 2202 (alkyne), 1585 (C═C), 1477 (aromatic), 1310 (aromatic), 1243 (C—O), 1172 (C—O), 977 (C—O), 837 (aromatic).

Provenance & Evidence