Structural isomer distribution in ring polymers of propylene oxide

Specific Formation of Cyclic Tetramer in Oligomerization of (R)-tert-Butyloxirane with Boron Trifluoride Etherate, and NMR and ORD Studies of the Cyclic Tetramer

“…2, 1977 in the preferred conformations of the linear polymer (G+G-T) and of the cyclic tetramer (G+G+T). Under the conformation of G+G+T, methylene carbons in the cyclic tetramer (7) come close to each other ( Figure 6). Thus, the observed higher field shift of the methylene carbon signal of the cyclic tetramer might be interpreted in terms of the steric compression shift, 16 magnetic anisotropy effect, and some other factors.…”

“…The ORD spectra of the cyclic tetramer (7) in benzene, in cyclohexane, and in chloroform are shown in Figure 7. In contrast to the corresponding linear poly(alkyloxirane)s, 3 ' 12 the ORD curve of the cyclic tetramer (7) in cyclohexane is exactly the same as that in benzene and very similar to that in chloroform.…”

“…According to our previous study of the ORD properties of linear poly(alkyloxirane)s, 3 ' 12 the different ORD behaviors in cyclohexane and in benzene can be ascribed to the different degree of interaction between solvent molecules and the main chain of the polyether, i.e., a smaller degree of interaction was observed in the poly-(alkyloxirane) having the bulkier side group. The similarity of the ORD spectra of the cyclic tetramer (7) in benzene and in cyclohexane indicates the absence of an appreciable interaction of solvent molecules with the main chain. This indication may be explained by the proposed structure of the cyclic tetramer (7) (Figure 6), where the ether oxygen atoms are insulated from the solvent by the bulky hydrocarbon groups.…”

“…(i) 1 H NMR. The 1 H NMR spectrum of the cyclic tetramer (7) in deuterated chloroform is shown in Figure 2. The methine-methylene part of the spectrum (o 2.8-4.0 ppm) was analyzed as an ABC spin system with the aid of a LAOCN3 simulation program.…”

Characterization of Polyurethane Foam Odor Bodies

“…Cyclic ethers of ethylene and propylene oxide are well known and can be readily prepared by reacting the epoxides with anhydrous Lewis acids [1][2][3][4][5][6]. Treatment of propylene oxide with BF 3' OEt2 in methylene chloride solvent yielded a multitude of cyclic products (Figure 4).…”