Dimethyloxirane Isobutylene Oxide

Similar results were obtained by Vandenberg2A). Thus, the polymerization of isobutylene oxide with BF3 (5 mol %) at 0 °C after 1 hr. gave 3 % of ether insoluble protic acids as initiators [SnCl4, BF O(C2H5)2, H0S02CF3] and found a 100% conversion to cyclic oligomers with n = 2-5 28). 

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There is, however, still some doubt whether the polymerization of 2,2-dimethyloxirane (isobutylene oxide) also proceeds by Sn2 attadc. This monomer is the best candidate for the SnI mechanism of propagation, because the generated dimethylcarbenium ion would be highly stabilized by the inductive effect ... 

Isoamyl acetate see 3-Methylbutyl ethanoate Isoamyl alcohol see 3-Methylbutan-l-ol heta.-Isoamylene see 2-Methylbut-2-ene Isohutane see 2-Methylpropane Isohutanoic acid see 2-Methylpropanoic acid Isohutanol see 2-Methylpropan-l-ol Isobutene see 2-Methylpropene Isobutyl acetate see 2-Methylpropyl ethanoate Isobutyl alcohol see 2-Methylpropan-l-ol Isobutylbenzene see (2-Methylpropyl)benzene Isobutyl chloride see l-Chloro-2-methylpropane Isobutylene see 2-Methylpropene Isobutylene oxide see 2,2-Dimethyloxirane Isobutyl ethanoate see 2-Methylpropyl ethanoate Isobutyl methyl ketone see 4-Methylpentan-2-one Isobutyraldehyde see 2-Methylpropanal Isobutyric acid see 2-Methylpropanoic acid Isocyanic acid butyl ester see Butyl isocyanate Isohexane see 2-Methylpentane Isooctane see 2,2,4-Tiimethylpentane Isopentane see 2-Methylbutane Isopentanol see 3-Methylbutan-l-ol Isopentyl alcohol see 3-Methylbutan-l-ol Isoprene see 2-Methylbuta-l,3-diene Isopropanol see Propan-2-ol Isopropenylbenzene... 

With a further shift in the direction of still more advanced breaking of the bond within active species this borderline S 2 mechanism could eventually convert into the S l mechanism. This should be promoted by the presence of a stabilizing group located close to the carbenium ion (like in the polymerization of cyclic acetals) and/or high ring strain (like in the three-membered rings). Indeed, contribution of the SnI mechanism in both cases has been postulated for polymerization of 1,3-dioxolane and isobutylene oxide (2,2-dimethyloxirane) but there is still no clear-cut evidence for its operation. This is probably the reason for high kinetic poiymerizabiiity of these monomers. 

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