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

Poly(vinyl amine) (PVAm) reacts with acetone in aqueous solution. It generates imine and aminal moieties along the PVAm backbone. The molecular structure of acetone-modified PVAm is confirmed by liquid H-1 and C-13 as well as solid state C-13 NMR and ATR-FTIR spectroscopies. Model compounds produced from 1,3-diaminopropane with acetone in chloroform are used to assign the solid state C-13 NMR signals of the modified polymer. Quantitative elemental analysis of acetone-modified PVAm samples supports the analytical results. The mechanism of the imine and aminal formation is discussed with regard to the anomeric stabilization of the incipient hemiaminal intermediate. The rapid and unexpectedly favorable formation of PVAm acetone hemiaminal, acetone imine, and aminal formation has implications for the conduct of PVAm research and even the interpretation of prior published results. As acetone was often used in the past to precipitate waterborne PVAm derivatives, this finding has a severe impact on the interpretation of research results. The consequences and the revised interpretation of selected publications are discussed.