Solvolysis of 9-(N-chloro-N-methylamino)fluorene (1-Cl) in 25 vol % acetonitrile in water gives the imine fluorenylidenemethylamine (3) as the sole product. The kinetic deuterium isotope effect was measured with the deuterated analogue (9-H-2)-9-(N-chloro-N-methylamino)fluorene as k(H)/k(D) = 4.8 +/- 0.2 (50 degrees C) without base and k(H)/k(D) = 6.7 +/- 0.2 (25 degrees C) with hydroxide anion. The solvent- and base-promoted reactions of 1-Cl are concluded to be of E2 type. The corresponding substrates 9-(N-4-Y-benzenesulfonyl-N-methylamino)fluorene (2-Y, Y = OMe, Me, or Br), with very poor leaving groups, show reversible E1cB reactions with added bases. The strongly activated substrate 9-(N-4-nitrobenzenesulfonyl-N-melhylamino)fluorene (2-NO2) does not give any elimination; it exclusively undergoes intramolecular nucleophilic aromatic substitution involving rate-limiting hydron transfer.