Phthalaldehyde was found to undergo cyclopolymerization with ease by several cationic catalysts and by γ‐ray irradiation. The polymer was composed entirely of the dioxyphthalan unit, as confirmed by infrared spectroscopy and ready decomposition to monomer. The enhanced polymerizability of phthalaldehyde as compared with other aromatic aldehydes was explained in terms of the intermediate‐type or, preferably, concerted propagation scheme. The conversion reached a saturation value of 87% in about 1 hr in methylene chloride at −78°C, indicating an equilibrium polymerization. The ceiling temperature of the polymerization was −43°C, as estimated from the relation between the saturation yield and polymerization temperature. The enthalpy and entropy of propagation were −5.3 kcal/mole and −23.0 eu, respectively. Since the molecular weight of the polymer was proportional to conversion, the propagating chain end was considered to be “living” in this system. The rate constant for propagation was calculated to be 0.18 1/mole‐sec in methylene chloride at −78°C with BF3OEt2 catalyst.
Abstract3,4‐ and 3,5‐Dimethylcyclopentenes were prepared as model compounds of the structural unit in polycyclopentadiene. These two isomers give characteristic NMR spectra. The assignment based on the 60 Mc./sec. spectrum was further confirmed by decoupling experiments on the 100 Mc./sec. spectrum of 3,5‐dimethylcyclopentene. By comparing the NMR spectra of these compounds with that of polycyclopentadiene methods were developed for estimating the polymer structure from the relative peak area of the methine–methylene and olefinic protons. Polycyclopentadiene obtained with Friedel‐Crafts catalysts at lower temperatures was shown to be composed mostly of the 1,4 and 1,2 structures. Polycyclopentadiene obtained with several Ziegler‐type catalysts possessed comparable amounts of both structures, contrary to the earlier proposals.
A stereochemical scheme of propagation was proposed for polymerizations of vinyl and related monomers by Friedel‐Crafts catalysts. For the cationic propagation proceeding via the simple carbonium ion pair, the following two factors were considered to be of primary importance in determining the steric course of propagation: (1) the conformation of the last two units of the propagating polymer segment and the direction of approach of the incoming monomer; (2) the tightness of the growing ion pair. Thus, the front‐side (less hindered site) attack to the carbonium ion gives rise to a syndiotactic placement and the back‐side attack an isotactic placement. The present model can satisfactorily explain the effects of substituents, catalysts, polymerization media, and polymerization temperature on the steric structure of polymers in cationic polymerization of vinyl ethers. Extension of the scheme to polymerization of the β‐substituted vinyl ethers in nonpolar solvents predicts formation of the diisotactic structures consistent with the experimental result. The influences of the polymerization condition on the steric structure of polymer were studied for cationic polymerizations of α‐methylstyrene at low temperatures. Highly syndiotactic polymers were obtained for homogeneous reactions in toluene‐rich media. The isotactic unit increased by increasing the content of methylcyclohexane in the solvent mixture. The effect of catalysts, though insignificant in toluene‐rich media, was clearly noted in methylcyclohexane‐rich media, less active catalysts (e.g., SnCl4) yielding higher amounts of the isotactic unit than more active catalysts (e.g., AlCl3). These results can be readily accommodated in the present model.
Inhibitory actions of several organic compounds on the enzyme-like catalysis of a watersoluble copolymer of 1-vinyl-2-methylimidazole and N-vinylpyrrolidone were studied in the hydrolysis of 3-nitro-4-acetoxybenzoic acid. The hydrolyses were carried out in 1 M KCl at 30 ' C, pH 8.0, using a pH-stat system. The inhibitions were analyzed by the LINE-WEAVER-BURK plotting of the MICHAELIS-MENTEN equation as in enzymatic reactions. Benzyl alcohol, the 2.4-dinitrophenolate anion, and dioxane competitively inhibited the enzyme-like catalysis of the polymer catalyst, Ki (inhibition constant) being 110, 42, and 1000 (10-3 mole .1-1), respectively. Acetone showed a mixed-type (competitive plus noncompetitive) inhibition. The rate-depressing effect of the product, the dianion form of 3sitro-4-hydroxybenzoic acid, could not be included in the common category of inhibition.
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