On the Ring Opening Reaction of ε-Caprolactam Derivatives

Abstract The ring-chain equilibria, (Remark: Graphics omitted.) were investigated experimentally for ε-caprolactam derivatives and their results could be analyzed by the method similar to that for ε-caprolactam. For the monomethyl derivative the equilibrium shifts to the ring-form and ΔH has been estimated to be 2.3 kcal/mol. which is smaller than ΔH(=3.5 kcal/mol.) for the unsubstituted. For dimethyl and N-methyl or -methylol derivatives equilibria shift too much to the ring-form to give polymers at high temperatures. The average unit of the Brownian motion of polymer chain molecules, i. e. the segment, for the monomethyl derivative is 13.3 skeleton atoms which is smaller than 19 skeleton atoms for unsubstituted polycapramide; the substitution makes it easier for chain molecules to be kinky.