2-Methyl-1 -butene, isomerization/hydrogenation

The amides of alkali and alkaline-earth metals catalyse hydrogen exchange in hydrocarbons even in the absence of liquid ammonia. For example, the heterogeneous deuterium exchange of benzene and 2-methylbutene-l occurs with a considerable velocity on solid KND2 and Ca(ND2)2 at 70°. This gives rise to the isomerization of 2-methyl-butene-1 to 2-methylbutene-2 (Shatenshtein et al., 1958a). 

The influence of sulfur introduced in thiophenic form to the hydrocarbon feedstock (2-methyl-l-butene), on presulfided catalysts, has been studied (61). The 2-methyl-l-butene is isomerized to 2-methyl-2-butene and is hydrogenated to isopentane. The influence of thiophene on the isomerization/hydrogenation ratio is indicated in Table XI for two presulfiding values 0.125 and 0.33. 

Figure 8.8. Adsorbed states of isoprene (2-methyl-1,3-butadiene) as alternative 71 0 structures and their half-hydrogenated states, leading to the three isomeric 2-methyl butenes. - ...

Rare Earth Oxides. Rare earth oxides such as La203 act as solid bases (2,9,15). The catalytic activities of rare earth oxides depend on their pretreatment temperature and the maximum activities of La203 for 1-butene isomerization, H-D exchange between CH4 and D2, and hydrogenation of 1,3-butadiene appear at a pretreatment temperature of923 K. Rare earth oxides show unique selectivity in dehydration of alcohols. 1-Alkenes are selectively produced from 2-alkanols such as 4-methyl-2-pentanol. 

Bromination of isoprene using Br2 at —5 ° C in chloroform yields only /n j -l,4-dibromo-2-methyl-2-butene (59). Dry hydrogen chloride reacts with one-third excess of isoprene at —15 ° C to form the 1,2-addition product, 2-chloro-2-methyl-3-butene (60). When an equimolar amount of HCl is used, the principal product is the 1,4-addition product, l-chloro-3-methyl-2-butene (61). The mechanism of addition is essentially all 1,2 with a subsequent isomerization step which is catalyzed by HCl and is responsible for the formation of the 1,4-product (60). The 3,4-product, 3-bromo-2-methyl-1-butene, is obtained by the reaction of isoprene with 50% HBr in the presence of cuprous bromide (59). Isoprene reacts with the reactive halogen of 3-chlorocyclopentene (62). 

Toluene reacts with carbon monoxide and butene-1 under pressure in the presence of hydrogen fluoride and boron trifluoride to give 4-methyl-j iYbutyrophenone which is reduced to the carbinol and dehydrated to the olefin. The latter is cycHzed and dehydrogenated over a special alumina-supported catalyst to give pure 2,6- dim ethyl n aph th a1 en e, free from isomers. It is also possible to isomerize various dim ethyl n aph th a1 en es to the... 

This is the most dubious in the case of Pd catalysts, which have high activity in isomerization and double-bond migration. From studies of the half hydrogenation and the isomerization of isoprene130 with Pd, Pt and Ni, the Pd catalyst led to the highest extent of isomerization. From the results of the reduction of isoprene it appears that 1,4-addition as well as 1,2- and 3,4-additions took place, because a significant amount of 2-methyl-2-butene was formed with all catalysts. 

The preparation of acyclic allylic hydroperoxides has been described before (3, 7, 9), but it is not clear how the reactivities differ from the better known saturated hydroperoxides and cyclic allylic hydroperoxides. Dykstra and Mosher prepared allyl hydroperoxide by the reaction of allyl methanesulfonate with hydrogen peroxide and alcpholic potassium hydroxide and purified the hydroperoxide by gas chromatography. It detonated on heating and decomposed on exposure to light but was relatively stable in the cold and dark. The isomeric allylic hydroperoxides formed from the autoxidation of the branched olefin, 4-methyl-2-pentene, have also been isolated and were not abnormally reactive (3). In the present study, cis- and trans-2-butene were photooxidized in the presence of methylene blue as a sensitizer (14), and the product, l-butene-3-hydro-peroxide, was isolated by preparative chromatography. 1-Butene proved unreactive and 2-butene-l-hydroperoxide could be formed only by isomerization of the secondary hydroperoxide. 

The absence of free isomerized olefins, the Constance of isomeric composition of the products throughout the whole reaction in hydro-formylation experiments of 1-pentene and 4-methyl-1-pentene under high carbon monoxide pressure, the distribution of deuterium in the hydro-formylation products of 3-methyl-l-hexene-3-di and 3-(methyl-d3)-l-butene-4-d3, and the results of carbonylation of olefins containing a quaternary carbon atom indicate initial formation of an olefin-cobaltcarbonyl complex. Isomerization of this complex, resulting in 1,2 hydrogen shifts in its organic moiety, can produce the necessary precursors of the various aldehydes that are formed. 

It is noteworthy that the isomerization of cis-2-butene taking place on the edge surface required a hydrogen cocatalyst, but the isomerization of 2-methyl-1-butene on the basal plane occurred in the absence of hydrogen. 

Effects of Crystal Size of MoS2 on the Isomerization of 2-Methyl-1-butene and the Hydrogen Exchange between C2HA and C2DA... 

Isomerization of 2-methyl-1-butene Hydrogen exchange of C2H4C2D4 1112 10 5 x 0 3 1 4... 

The only available aldehyde data are for isomerization of butanal to 2-methylpropanal for which AHisom(g) = —11.0 1.7 kJmol-1. The corresponding alkene isomerization enthalpy of 1-pentene to 3-methyl-1-butene is —6.2 0.9 kJmol-1. Hydrogenating all... 

Fig. 1.56. In the example depicted in this figure, a bifunctional catalyst like platinum on silicon oxide enables the isomerization of methyl-cyclopropane to buten-2 as well as its hydrogenation to butane [349]. The isomerization proceeds on the oxide support. Hydrogen dissociates on the metal particle and the H-atoms spillover onto the oxide support material where they are mobile to react with butene...

Make a model of ethyne. Now replace the hydrogens with methyl groups to get 2-butyne. Compare to 2-butene which exhibits cis-trans isomerism. Why does 2-butene show geometric isomerism but not 2-butyne ... 

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