Isobutene reaction with

Figure 9.14. Alkylation of isobutane and propene is a chain reaction with the isobutene carbenium ion as the chain carrier (indicated...

The reactions of Y with four butene isomers, namely 1-butene, cis-2-butene, trans-2-butene, and isobutene, were studied at a collision energy (/ ycoii) of 26.6kcal/mol (see Table 2). In reactions with 1-butene and cis- and trans-2-butene, four processes were observed ... 

Reactions with isobutene led to channels (5), (7), and (8), but no evidence for process (6) was observed. Time-of-flight (TOF) spectra for all four isomers were similar, so only data for the Y + cis-2-butene reaction will be shown. A Newton diagram for this reaction is shown in Fig. 33. 

Adib A process for extracting isobutene from petroleum fractions by reaction with phenol. The reaction takes place in the gas phase, over an acid catalyst, and yields all the mono-, di-, and tri-butyl phenols. Heating this mixture liberates isobutene the phenol and the catalyst are recovered for re-use. Piloted in Argentina in the 1980s. 

Hydride transfer from alkenes was also proposed to occur during sulfuric acid-catalyzed alkylation modified with anthracene (77). Then the butene loses a hydride and forms a cyclic carbocation intermediate, yielding—on reaction with isobutene—trimethylpentyl cations. This conclusion was drawn from the observation of a sharp decrease in 2,2,3-TMP selectivity upon addition of anthracene to the acid. 

In this chapter we will be concerned mainly with the formation of high polymers of isobutene, and with the fundamental studies aimed at the elucidation of this reaction. There is no doubt that many useful hints of fundamental interest are to be found in the patent literature, but in most cases the purity of the reagents and the reaction conditions are so ill defined, that no conclusions can be drawn from findings reported in patents. The ratio of scientifically valuable to dubious information in patents is so small that detailed survey of them, in the hope of discovering sound information, should be a most unrewarding occupation. This is more or less true of all chemical patents, but especially so in this particular field where minute traces of impurities can effect catastrophic changes in the reaction pattern. For this reason attention has been confined to work published in the scientific literature. 

The inertness of isobutene to radicals and anions, and its ready reaction with cations have produced a conviction that the activity of every catalyst which will polymerise... 

With ethyl bromide as solvent a brief, exploratory study [77] showed that the rates and DPs were more irreproducible than with other alkyl halides, and this was ascribed, at least partly, to the relatively high dissociation constant of ethyl bromide to ethylene and hydrogen bromide. No evidence was obtained whether ethyl bromide itself is a co-catalyst, and the putative co-catalyst in the reaction was residual water and possibly traces of t-BuBr formed from HBr and isobutene. Experiments with [C4H8] = 0.11-0.92 mole/1, [TiCl4] (2.7-11.2) x 103 mole/1, T = -38° to -103° showed that EDP = 5.5 0.5 kcal/ mole that below about -60° the DP is almost independent of monomer concentration and that kjkp = 2 x 10 4 at -63° and 8 x 10"5 at -71°. 

Isobutene - In contrast to the complicated picture presented by the polymerisations of most other alkenes, the polymerisation of isobutene at low temperatures is a clean reaction with apparently few complications [10, 16, 17, 18]. The propagation step seems to be a simple addition to the monomer of the tertiary carbonium ion at the growing end of the chain. This difference between the behaviour of isobutene and of most other olefins is so striking that isobutene could usefully be regarded as a standard of reference it would thus be possible to enquire into the behaviour of other olefins by comparing them and their polymers with isobutene and polyisobutene. 

A further support for the identification of the species responsible for the unimolecular conductance increase in terms of a chlorine-containing radical is the fact that in a blank experiment, i.e. one in which chloride is left out, a slow conductance increase is not observed and the overaU conductance yield is only half of that in the presence of chloride. Since in isobutene-saturated aqueous solution the lifetime of SOi is only 90 ns due to its rapid reaction with the alkene (as determined by optical experiments at 450 nm) [46], the non-observability of a unimolecular conductance increase means that the rate constant for heterolysis of the SO adduct to isobutene is 10 s" (cf. Eq. 32) ... 

The iridium(III)-complex, [Ir(p-acac-0,0,C )(acac-0,0)(acac-C )]2, mediates the activation of unactivated aromatic C—H bond with unactivated alkenes to form anti-Markovnikov products [57]. The reaction of benzene 131 with propene 132 (0.78 MPa of propylene, 1.96 MPa of N2) leads to the formation of n-propylbenzene 133 in 61% selectivities (turnover number (TON) = 13 turnover frequency (TOE) = 0.0110 s ) (Equation 10.34). The reaction of benzene with ethane at 180 °C for 3h gave ethylbenzene (TON = 455 TOE = 0.0421s ). The anti-Markovnikov selectivity was also proven for the reaction with 1-hexane and isobutene, giving 1-phenyUiexane (69% selectivity) and isobutylbenzene (82% selectivity), respectively. 

The crude C4 fraction is extracted with acetone, furfural, or other solvents to remove alkanes such as -butane, isobutane, and small amounts of pentanes, leaving only 1- and 2-butenes and isobutene. The isobutene is removed by reaction with sulfuric acid and water because it reacts more easily, being able to form a tertiary carbocation. 

Derivatization of a-aminosuberic acid to produce selectively protected derivatives such as Z-L-Asu(OtBu)-OH 16 is performed as outlined in Scheme 6. Using Z-l-Asu-OH 13 as starting material, conversion into a-benzyl ester 14 by treatment with Bzl-Br, followed by reaction with isobutene/H2S04 and saponification of the benzyl ester 15 leads to the desired product 16 as the piperazine salt.124 ... 

It has been assumed 42 that triplet CH2 does not undergo the insertion reaction with C—H bonds, but there is no firm evidence to support this contention. Reaction of CH2 with isobutene, cis and trans butene-2, and cyclohexene (see Sec. IV-E) under conditions favoring formation of triplet methylene gave relatively higher yields of C=C addition products, but the insertion products were nevertheless present in each case. We believe that reduced yields of the insertion products result from lower methylene energy rather than a fundamental difference in reaction mechanism. 

Duncan and Cvetanovic27 studied the reaction with isobutene of methylene generated by the mercury photosensitized decomposition of CH2CO, which is believed to produce triplet methylene. Product ratios reached high-pressure limiting ratios at 200 mm. The observed yield of... 

A one-pot synthesis of the conjugated ketenedithioacetals (7) and (8) involving indirect lithiation of propene or isobutene via the potassio deriviative reaction with carbon disulfide and 5,5-dimethylation has been reported [68]. It illustrates some aspects of the reaction of organometallics with CS2. 

---