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The Mechanism of “Active Monomer” Polymerization of α‐Amino Acid N‐Carboxyanhydrides. Temperature Effects and the Significance of the Proton‐Transfer Reaction
Author(s) -
Goodman M.,
Jacobsberg L. B.,
Choi N. S.
Publication year - 1971
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.197100021
Subject(s) - chemistry , polymerization , monomer , kinetic isotope effect , arrhenius equation , chain growth polymerization , polymer chemistry , photochemistry , proton , bulk polymerization , reaction mechanism , ionic polymerization , reaction rate constant , activation energy , radical polymerization , kinetics , catalysis , deuterium , polymer , organic chemistry , physics , quantum mechanics
The temperature dependence of the polymerization rate is investigated using the NCA's of β‐benzyl L‐aspartate and γ ‐benzyl L‐glutamate. Activation energies for polymerizing the above NCA's are 13 and 9 Kcal per mole, respectively. Entropies of activation and Arrhenius constants, A, are also calculated and discussed in terms of the polymerization mechanism. The significance of the proton‐transfer reaction in the “active monomer” mechanism is recognized through a kinetic isotope effect and also by comparing the polymerization rates of L‐alanine NCA and its structural analog L‐alanine N‐thiocarboxyanydride. It is theorized that a changing position of equilibrium of the neutralization step decreases the concentration of “active monomer”, thereby slowing the polymerization rate.