Synthesis of 9,9-bis(4-hydroxyphenyl) fluorene catalyzed by bifunctional ionic liquids.

Through structural design, a series of bifunctional ionic liquids (BFILs) containing sulfonic acid (-SO 3 H) and sulfhydryl groups (-SH) were synthesized and characterized by NMR and MS. The acidity of these BFILs was measured by the Hammett acidity ( H 0 ) and the effective sulfhydryl molar content of BFILs was determined by Ellman's method. Moreover, BFIL's catalytic properties in the condensation reaction of 9-fluorenone and phenol were studied. BFIL catalyst 6c can achieve nearly 100% conversion of 9-fluorenone with a high selectivity of 9,9-bis(4-hydroxyphenyl) fluorene (95.2%).