Ethylene derivatives 2-methyl-2-butene

An MNDO calculation of six bromonium ions derived from ethylene, propene, 2-butene, isobutylene, 2-methyl-2-butene and tetramethylethylene, 49-54 shows energy minima corresponding to symmetrical bridged ions for symmetrically substituted systems 49-51 and highly asymmetric bridged ions for non-symmetrically substituted species 52-54107. 

Acetonitrile added dropwise with stirring at 3-8 to 92%-H.2SO y then 3-methyl-3-buten-l-oI added slowly at 8-10°, and stirred ca. 25 min. while allowed to warm to room temp. 2,4,4-trimethyl-5,6-dihydro-4H-l,3-oxazine. Y 48%. F. e. s. S. P. McManus and J. T. Carroll, Org. Prep. Procedures 2, 71 (1970) from nitriles, ethylene derivs., and formaldehyde cf. C. Giordano, G. Ribaldone, and G. Borsotti, Synthesis 1971, 92. 

We now proceed to primary-alkyl-%uhsi i xigA derivatives of ethylene, in which the energy of interaction between the substituents exceeds the interaction with the framework. In general, steric interactions between proximate alkyl groups have a major influence on both ground-state conformations and on barrier heights. Methyl substitution in 1-butene is illuminating (Scheme 7 Shimanouchi and Abe, 1968). 

Tacticity measurements can be correlated with reaction mechanisms and physical properties. For example, the incorporation of an electron donor into the polymerization catalyst formulation has been found to increase isotacticity in a propylene-1-butene copolymer [123], and the distribution of propylene and 1-butene contents as a function of molecular weight varied, depending on donor type. External donors, such as dimethox-ysilane, decrease the butene content more than internal electron donors (in this case, di-n-butyl phthalate). Mechanisms of new polymerization reactions, such as the group-transfer copolymerization of methyl methacrylate and lauryl methacrylate, can be elucidated by comparing NMR-derived structural details [124]. The presence of unanticipated peaks in the spectrum of poly(ethylene-co-norbomene) suggest the occurrence of epimerization... 

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