Fluorene resonance structures

Fig. 5 Fully conjugated indeno[l,2-h]fluorene 2 and resonance structures of 22...

The hydrocarbon with the common name fluorene is acidic enough (p a = 23) to be a useful indicator in deprotonation reactions of compounds of greater acidity. Indicate the most acidic hydrogen(s) in fluorene. Draw resonance structures to explain the relative stability of its conjugate base. 

A methylene group resonance which joins two ring structures (bridgehead) appears at lower magnetic field, Table 3. The singlets at 3.36 and 3.88 ppm in Fraction K can be assigned to acenaphthene and fluorene, respectively. 

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