Kinetic behavior of tetrachlorocyclopentadienyl-type anions. Deprotonation of 1,2,3,4-tetrachloro-1,3-cyclopentadiene and nucleophilic addition to 1,2,3,4-tetrachloro-6-phenylfulvene in 50% Me2SO/50% water

Abstract

The kinetics of the reversible deprotonation of 1,2,3,4-tetrachloro-1,3-cyclopentadiene by OH − , piperidine, piperazine, 1-(2-hydroxyethyl) piperazine, morpholine, 1-piperazinecarboxaldehyde, n-butylamine, 2-methoxyethylamine, 2-chloroethylamine, and glycinamide and of reversible nucleophilic addition of piperidine and morpholine to 1,2,3,4-tetrachloro-6-phenylfulvene have been measured in 50% Me 2 SO/50% water at 20°C. Bronsted coefficients and intrinsic rate constants have been determined for both the proton transfers and the nucleophilic additions. The significance of these intrinsic rate constants with respect to resonance effects in the tetrachlorocyclopentadienyl anions and transition-state imbalances is discussed. This paper also reports the first pK a determination of 1,2,3,4-tetrachloro-1,3-cyclopentadiene (pK a =8.32)