A number of 4-substituted 1,6-heptadienes have been prepared and their infrared absorption characteristics compared with their polymerizability. This group of compounds included several N,N-diallylamides, diallylcyanamide, diallyl-(tricyanovinyl)-amine, diallylammonium bromide, diallylmethylphosphine oxide, diallylphenylphosphine oxide, diallylmethylphenylphosphonium bromide, and dimethyl-4-penteneamine. The frequencies of the in-plane-deformation vibration of the terminal methylene groups varied from 1411 to 1437 cm−1. The higher frequencies were attributed to the electron withdrawal effect of the substituent in the 4 position. Those compounds having higher absorption frequencies also undergo polymerization more readily than those in the lower-frequency range. These correlations are presented as substantiating evidence for an intramolecular interaction in the monomers which can in part explain the facile but highly improbable cyclopolymerization mechanism.