Allyl cations defined

It should be noted that the kinetics were first-order over at least three half-lives (with the exception of the dicyclopropylcarbonium ion), but the reaction products were not well defined in some cases— probably due to relatively fast consecutive reactions of the unsatmated oxocarbonium ions formed. In the case of the oxocarbonium ions formed from the allyl cations a novel quantitative eyclization to give cyclopentenone derivatives was observed (Hogeveen and Gaasbeek, 1970) ... 

Figure 4.2 Hiickel MOs for the allyl system. One pc orbital per atom defines the basis set. Combinations of these 3 AOs create the 3 MOs shown. The electron occupation illustrated corresponds to the allyl cation. One additional electron in

Greek letter w for this purpose. Such to orbitals can interact in a suprafacial or antarafacial sense, as shown in Fig. 3.17. Thus a suprafacial interaction on the occupied -orbital of Xyz is designated 2 (where 2 indicates the presence of two electrons), whereas an antarafacial interaction on the unoccupied p-orbital is denoted by On this basis the electrocyclic conversion of the cyclopropyl cation into the allyl cation (Equation 3.19) is defined as a [ 2g + ] process if it occurs by the disrotatory mode indi-... 

Well-defined macromonomers of poly(BVE), poly(IBVE), and poly(EVE) with co-methacrylate end group [91] were prepared by living cationic polymerization of the corresponding monomers initiated by trifluoromethanesulfonic add in CH2C12 at -30 °C in the presence of thiolane as a Lewis base. After complete conversion, the polymers were quenched with 37 in the presence of 2,6-lu-tidine or with 41 to produce macromonomers with Mn up to 10,000 g mol-1, with narrow MWD, bearing one polymerizable methacrylate function per molecule. The same polymers were also quenched with 38 in the presence of 2,6-lutidine to give poly(vinyl ether)s with an allylic terminal group. 

All these developed living cationic polymerization methods for isobutene provide defined tertiary chloride end groups, opening up possibilities for further end-group functionalization. A representative example was reported by Ivan and Kennedy, who described the quantitative conversion of the chloride into allyl-terminated PIB, which was converted into epoxy and hydroxyl-functional PIBs [34]. 

The intrinsic limitation for the direct CROP of IV-H-cyclic amines for preparing defined linear PHAIs is the similar nucleophilicity of the amino groups of the monomer and the polymer. As such, the cationic chain ends are reactive towards both the monomer and the polymer, leading to the formation of hyperbranched polymers. Lower degrees of branching may be achieved by a mixed feed containing both aziridine and an N-suhstituted aziridine, but this also leads to the incorporation of allylated tertiary amine groups. ... 

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