A vinyl monomer that has the nitrile or carbonyl group conjugated to the CC double bond, such as acrylonitrile, methyl acrylate, and methyl methacrylate, forms a complex with an alkylaluminum halide, and the complex reacts spontaneously with a hydrocarbon monomer such as styrene, propylene, or ethylene, giving a high molecular weight copolymer. The copolymers always contain the two monomer units in 1:1 ratio. Thus styrene, copolymerized with methyl acrylate or methyl methacrylate in the presence of ethylaluminum sesquichloride in homogeneous toluene solution, gives such an equimolar copolymer regardless of the initial monomer compositions. The NMR spectra of these copolymers are distinctly different from those of the equimolar copolymers obtained with azobisisobutyronitrile as initiator and have simpler and well separated patterns. The copolymers and the corresponding radical copolymers appear to be amorphous, judged by their x‐ray diffraction patterns and their differential thermal analyses. Their infrared spectra resemble each other very closely. Hence, the difference in the NMR spectra may be ascribed to the matter of the sequence distribution. The infrared spectrum of ethylene–methyl acrylate copolymer shows no absorption near 720 cm.−1 due to the methylene sequence arising from ethylene–ethylene linkage. These experimental data lead to the inference that the equimolar copolymers obtained in this work may have an alternating sequence.

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synopaisThe monomer reactivity in the complexed copolymerization of vinyl compounds with alkylaluminum halides has been extensively surveyed. Equirnolar copolymers were obtained in various combinations of monomers which are classified into two monomer groups, A and B. The group B monomers are conjugated vinyl compounds having nitrile or carbonyl groups in the conjugated position and form complexes with alkylaluminum halides. The group A monomers are donor monomers having low e values, such as olefins, haloolefins, dienes, and unsaturated esters. These A monomers belong to the same group of monomers which give alternating copolymers in conventional radical copolymerization with rnaleic anhydride, SOz, and so on. In addit.ion the complexed copolymerization has the same specific characteristics as the conventional alternating copolymerization, i.e., high reactivities of allyl-resonance monomers and inner olefins and no transfer of halogen atom to the copolymers in CCl,. These features suggest little or no participation of the A monomer radical. The &-e scheme is also discussed in terms of the monomer reactivity. More than two monomers selected from groups A and B give multicomponent copolymers in which alternating sequential structures hold with respect to A and B. Anomalous mutual reactivities between two B monomers in the terpolymerization were observed and indicate that the nature of radical in the complexed copolymerization may be different from that expected by the Lewis-Mayo equation. The complexed radical mechanism previously proposed is discussed in connection with the specific behavior mentioned above. EXPERIMENTAL MaterialsMonomers. Ethylene, propylene, butadiene, vinyl chloride, and acrylonitrile were polymerization-grade reagents of the Sumitomo Chemical

The photobrominations of (+)-2-methylbutyl acetate, (-)-l-fluoro-2-methylbutane, and (+)-l-bromo-2-methylbutane were carried out with molecular bromine. The recovered nonbrominated fluoride and acetate had racemized to a large extent during the bromination reaction, while the bromide underwent only a small amount of racemization. The brominated fluoride, 2-bromo-l -fluoro-2-methylbutane, was found to be optically inactive while the 1,2-dibromide obtained as a product from the bromination of (+)-l-bromo-2-methylbutane, as was previously reported by Skell, Tuleen, and Readio, was found to be optically active. These results are discussed in relation to the general problem of bridged radical intermediates.

Can. J. Chem. 55, 612 (1977). A series of terf-butyl peresters having a general forn~ula corresponding to I were synthesized.The thermally initiated rates of decomposition of these peresters were determined at several temperatures and the activation parameters for these thermolyses were calculated. The rates of decomposition were relatively insensitive to the substituents and followed the order I > C2H, > C6H5S > H > Br > C1. The activation parameters and product studies were consistent with a simple two bond scission mechanism and no evidence could be found for neighboring group participation in these homolyses.

The kinetic scheme of the alternating copolymerization of a donor monomer and an acceptor monomer complexed with an alkylaluminum halide was studied to investigate the reaction mechanism. In the alternating copolymerization of styrene (St) and methyl acrylate (MA) complexed with aluminum ethylsesquichloride (A!Et1.5Cl,. 5), the kinetic data were expressed by the following equation(!). Rp=k 0 [MAJ1. 0 [AIEt1.5Cl1.sJ1.o[StJ 0 (I) Based on eq I together with the experimental observations the reaction mechanism of the alternating copolymerization was discussed.

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