Influence of the Reaction Conditions and Molecular Structure on the Kinetic of the Nucleophilic Aromatic Substitution of Fluoro Compounds with Poly(vinyl amine) in Water

Abstract

The nucleophilic aromatic substitution (NAS) reaction of various fluoroaromatic/2,6‐O‐dimethyl‐β‐cyclodextrin complexes with poly(vinyl amine) (PVAm) has been studied in water at different pH. Increasing pH lowers the notable negative activation entropy of those types of NAS due to the PVAm chain segments becomes better accessible in basic media. At pH > 7, the zwitterionic intermediate in the course of NAS seems stabilized by intermolecular hydrogen bonds, which has an influence on the increase of activation energy for elimination the fluoride ion. As a consequence, the counter balance between activation entropy and activation energy determines the rate of the NAS with PVAm, which is shown for several functional fluoroaromatic compounds including fluoronitrobenzenes, fluoronitroanilines, and imine bases.

The Reaction of Poly(Vinyl Amine) with Acetone in Water

“…By coincidence, the new 13 C NMR signal appears at the same chemical shift as poly(vinyl alcohol) (PVAl). However, our numerous studies in PVAm chemistry did never hint at the formation of PVAl moieties along PVAm chains …”

“…However, for detailed molecular structure investigations it may be necessary to segregate chemically modified PVAm samples from its aqueous solution. This can be the case when PVAm has reacted with electrophilic reagents, for example, with carboxylic acid anhydrides, lactones, aldehydes, or fluoronitroaromatics …”

“…In previous works we studied the nucleophilic aromatic substitution of activated fluoro aromatics and highly reactive carbonitrile compounds with PVAm as reagent in aqueous solution to produce solvatochromic, acidochromic, and fluorescent polymers . For some modified solid PVAm/silica hybrid samples even a signal in the range of 65 ppm was observed in the solid state 13 C NMR spectrum.…”