Novel spontaneous polymer formation from acetaldehyde azine and maleic anhydride via radical mechanism

A THF-insoluble polymeric product was obtained by the reaction between acet aldehyde azine (AcAz) and maleic anhydride (MAnh) without any initiator. Th e reduced viscosity values for this product indicate polymer formation from AcAz and MAnh. Results of the reactions between AcAz and MAnh at varying f eed ratios of AcAz indicate that the polymer is formed mainly by reaction b etween equimolar amounts of AcAz and MAnh. (2Z)-4-{1-(5-Methyl-2-pyrazoliny l)}-4-oxo-2-butenoic acid (compound 1), a one-to-one adduct of AcAz with MA nh, was isolated as a crystalline compound from the THF-soluble fraction of the reaction mixture. Comparing the spectroscopic results for the polymer with those for compound 1 and 4-{1-(5-methyl-2-pyrazolinyl)}-4-oxobutanoic acid (compound 2), a one-to-one adduct of AcAz with SAnh, the polymer from AcAz and MAnh was found to be formed mainly by polymerization of compound I through the C=C bond. Results of the polymerizations of compound 1 using t ypical initiators show compound 1 can be polymerized by radical initiators, indicating that the polymer from AcAz and MAnh is formed by a radical mech anism. On the basis of the electron-donating property of 5-methyl-2-pyrazol ine (compound 3) formed by isomerization of AcAz in the presence of compoun d 1, the spontaneous polymer formation from AcAz and MAnh was inferred to b e initiated by electron transfer from compound 3 to compound 1.