NEW MONOMERS AND POLYMERS - 5. STUDY OF THE SPONTANEOUS POLYMERIZATION OF 5-ETHOXYCARBONYL-3-FORMYL-2-PYRAZOLINE.

Results of an experimental investigation are presented which show that the 3-formyl-2-pyrazolines (pyrazoline-3-carboxaldehyde) obtained by 1-3 dipolar additions of diazoesters to acrolein are unstable and smoothly polymerize through the aldehyde group to a polyacetal polymer. On the basis of spectroscopic data, this paper describes the structure of the isolated polymers, along with their properties and a polymerization mechanism. It is propsoed that a nucleophilic attack of heterocyclic amino nitrogen on another monomer formyl group leads to an internal ion pair, and that this latter promotes a polycondensation of other aldehydic units according to an anionic type of propagation. The results are polyacetal polymers of low molecular weight with conservation of the heterocyclic framework. However, numerous side reactions are possible and account for the relatively low molecular weights observed.