Resonance effect of amide group on the polymerizability of lactam derivatives. III. Polymerization of many‐membered lactams ring

Abstract

AbstractThe polymerization rate of many‐membered lactams in the presence of water and the equilibrium constant of the addition reaction between lactam and hydrogen chloride were measured to investigate the relationship between the conformation, resonance effect, and polymerizability of lactams. The polymerization velocity of lactams in the presence of the same amount of water is in the following order: 8‐membered lactam > 7‐membered lactam > 11‐membered lactam ≫ 5‐ and 6‐membered lactams. The polymerizability reaches a maximum with the 8‐membered lactam. The equilibrium constant K of the addition reaction between lactam and hydrogen chloride reaches a maximum with the 7‐membered lactam and the basicity of the lactams is highest with the 7‐ or 8‐membered lactam. The conformation of the amide group of the less than 6‐membered lactam is a cis form, while that of the 6‐ to 8‐membered lactam is a mixture of the cis and trans forms, and an equal number of cis and trans forms is found in the 8‐membered lactam in the infrared spectrum. From these results it is concluded that when the two conformations of the amide group become equal, the resonance effect of the amide group decreases, resulting in an increase in the polymerizability of lactam.