Isobutylene, displacement

The rate of the r-BuX + Me3Al M X > f-BuMe + Me2AlX reaction decreases as X = Cl > Br > I10. This decrease is explained by a decrease in the rate of displacement of MeX by r-BuX, which in turn is determined by the basicity and/or size of the halogen in f-BuX. Since the basicity decreases and size increases as X changes from Cl to Br to I, the rate of displacement, R, decreases. In isobutylene polymerization using f-BuX/Me3Al/MeX and r-BuX/Et2 AlCl/MeX (X = Cl, Br, I), the r-BuX reactivity decreases as f-BuCl > f-BuBr > r-BuI = 0. The similarity between initiator reactivity sequences in model and polymerization reactions indicates that the rate governing event is the same for both, i.e the rate of displacement, R1. 

Isobutylene recovered from an experiment with a mole ratio of 3 olefins/Cl3SiD contained C—D bonds. This requires that deuteroisobu-tylene was displaced by isobutylene from the complex in a reversible way to lead to equilibrium between olefin molecules in solution and those in the complex. 

The product (benzyl f-butyl ether) is primary on the benzyl side and tertiary on the t-butyl side. So, an SN2 type displacement by potassium f-butoxide of benzyl bromide is one approach, and an acid-catalyzed (SN1) process of benzyl alcohol with isobutylene (2-methylpropene) is another method ... 

Determination of the amount of 14C-labelled A1R3 adsorbed on TiCl3 2) allows an estimate of both types of centers together. To determine type II centers in VClj/AliBiij and TiCl3/AliBu3 systems, Burfleld 331 used styrene or a-methylstyrene to displace isobutylene from the center. The amount of tritiated cumene formed after alcoholysis (MeOT) of the product of displacement was equal to the amount of... 

As Eq. 4.4 describes, the initial intermediate is most plausibly the psuedoequatorial iodonium ion 219a having the equatorial sidechain. Displacement by the carbonate oxygen via a six-membered ring transition state results in formation of the oxo-stabilized cation 210b. Loss of isobutylene then produces the c/j-substituted iodocarbonate 220. 

Closely related to these results is the fact that trialkyl alanes of the triisobutyl type give the growth reaction only partially with ethylene 53). The concurrent reaction is the displacement to give triethylalane and an alkene of the isobutylene type ... 

The formation of chelating diolefin complexes by displacement of olefin ligands is rare because complexes containing two monpolefin ligands in suitable mutual positions to be replaced by one diene ligand are themselves rare. Thus diolefins such as 1,3-cyclohexadiene, 1,4-cyclohexadiene and nbrbornadiene all displace isobutylene from [Fe( 7 -Cp)(CO)2(isobutylene)][BF4], but only one double-bond of the diolefin coordinates to the iron . Diolefins readily displace 1,5-cyclooctadiene from Ru(1,5-COD)(CO)3 to form new diolefin complexes ... 

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