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1.6- Dimethylcyclohexene trans isomer

Nevertheless, during hydrogenation of the dimethylcyclohexenes, the fact that the quantities of trans isomer increase with the double bond migration ability of the various catalysts90 suggests that double bond migration sites (or the sites nearby) are involved in apparent trans addition. [Pg.43]

In contrast to 1,2-dimethylcyclohexene, methyl cyclohexene-1,2-dicarboxylate was reported to yield only the cis saturated product in the hydrogenation over platinum oxide in acetic acid at 26-27°C, independently of the pressure of hydrogen (0.1-20 MPa) and the concentration of the substrate (0.05-1,0M).140 Hydrogenation of methyl cyclohexene-1,6-dicarboxylate also gave the same result at about 1 atm H2, but some of the trans isomer (6+2%) was formed at a pressure of 13 MPa H2. [Pg.103]

Sabadie and Germain [20] have investigated the stereoselectivity of polymer-supported metal catalysts in the hydrogenation of 1,2-dimethylcyclohexene. Depending on the pressure of hydrogen, different ratios of cis- and trans-isomers (0.44 and 0.57 at 1.25 and 10 MPa, respectively) of 1,2-dimethylcyclohexanes were obtained over Pd/APSDVB catalysts. [Pg.318]

If the hydrogenation reaction consisted solely of the one-sided addition of hydrogen to a double bond, then pure cfs-1,2-dimethylcyclohexane should be obtained from 1,2-dimethylcyclohexene however, only 77% of the expected isomer was formed. Conceivably, the introduced olefin might isomerize to one in which the groups are trans or to an olefin which can yield the trans isomer by a one-sided addition of hydrogen, for example,... [Pg.20]

The hydrogenation of substituted cyclic alkenes is anomalous in many cases in that substantial amounts of rran -addition products are formed, particularly with palladium catalysts. For example, the alkene 19 on hydrogenation over palladium in acetic acid gives mainly frans-decalin (7.12), and the alkene 1,2-dimethylcyclohexene 20 gives variable mixtures of cis- and trans-, 2-dimethylcyclohexane depending on the conditions (7.13). Similarly, in the hydrogenation of the isomeric dimethylbenzenes (xylenes) over platinum oxide, the cis-dimethylcyclohexanes are the main products, but some trans isomer is always produced. [Pg.412]

Nearly equal amounts of the major product enantiomer (of the trans product) are formed, and in both cases, there is a preference for suprafacial use of the allylic moiety. However, there is roughly twice as much product resulting from antarafacial use of the allylic moiety in from the starting cis isomer as from the trans isomer which comes at the expense of the cw-dimethylcyclohexene which is the result of a suprafacial use of the allylic moiety. A factor of two, however, represents only 0.8 kcal/mol at this relatively high temperature. [Pg.156]

Metals differ in their ability to catalyze isomerizations. Both the relative rates of isomerization of individual alkenes and the initial isomer distribution vary with the metal. The rates of isomerization of the three n-butenes on ruthenium and osmium, for example, are cis-2- > trans-2- > 1-butene,175 whereas on platinum and iridium they are cis-2- > 1- > trans-2-butene.176 These observations are in accordance with the fact that the rates of formation of the 1- and 2-butyl intermediates are different on the different metals. The order of decreasing activity of platinum metals in catalyzing the isomerization of dimethylcyclohexenes was found to be Pd Rh,... [Pg.186]

The hydrogenation of 1,2-dimethylcyclohexene (17 Pt02, HOAc, 1 atm) yields trans-(19) as well as cis-1,2-dimethylcyclohexane (18), but Ir and Os in t-butyl alcohol are much more selective (equation lb). The addition of hydrogen to (17) competes with isomerization to 1,6-dimethylcyclohexene (20), which not only reacts more rapidly but yields trans (19) as well as the cis product (18) via syn addition of the two hydrogen atoms (equation 17). In the Pt-catalyzed reaction, the intermediate (20) can be observed, although its steady-state concentration remains low (0.21% of the 1,2-isomer 17) because of its... [Pg.426]

Solution 19 Cis-lrans stereoisomers are possible only for 3,4-dimethylcyclohexene. The ring size and geometry of the double bond prohibit a trans configuration of the double bond. Two configurational isomers (they are enantiomers) are possible for 2,3-dimethylcyclohexene. [Pg.697]


See other pages where 1.6- Dimethylcyclohexene trans isomer is mentioned: [Pg.168]    [Pg.40]    [Pg.623]    [Pg.855]    [Pg.157]    [Pg.62]    [Pg.66]    [Pg.101]    [Pg.112]    [Pg.30]    [Pg.20]    [Pg.251]    [Pg.42]    [Pg.156]    [Pg.96]    [Pg.42]    [Pg.130]    [Pg.130]   
See also in sourсe #XX -- [ Pg.163 ]




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1.2- Dimethylcyclohexene

Dimethylcyclohexenes

Trans isomers

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