Question

Fluorenone can be synthesized from fluorene by reaction with NaOH in the presence of oxygen and a catalyst. The first step of the reaction is deprotonation of fluorenone. CH bonds normally have a pK_a in the 50+, but the pK_a of fluorenone is estimated to be 22-23 in dimethylsulfoxide. a) Which hydrogen of fluorenone is deprotonated by NaOH? b) Why is fluorenone so easy to deprotonate compared to a "normal" CH bond. Justify your answer appropriately.

Answer 1

The question has some printing error. Fluorenone cant be deprotonated, its fluorene which is deprotonated to get fluorenone. Pk_a value and synthesis of fluorenone confirms the error. However, the fluorene has CH2 which is called C-9H position. The C-atoms are numbered as unattached from a common ring are first, then others.This position after deprotonation gives the system aromaticity thats why it is acidic.

Fluorene Pka 23Deprotonahen Fluorenene PKa 40-45 1ine syste v gets aromaticity Hücket fude (4nt1ne n-3