Decalin trans isomer

Property Tetralin cis Decalin Mixed isomers trans... 

The decalin (bicyclo[4.4.0]decane) ring system provides another important system for study of conformational effects in cyclohexane rings. Equilibration of the cis and trans isomers reveals that the trans isomer is favored by about 2.8 kcal/mol. Note that this represents a change in configuration, not conformation. The energy difference can be analyzed by noting that the cis isomer has three more gauche butane interactions that are... 

Figure 4.17 Representations of cis- and frans-decalin. The red hydrogen atoms at the bridgehead carbons are on the same face of the rings in the cis isomer but on opposite faces in the trans isomer.

ESR spectra for, 22 294, 301 as high-energy fuels, 18 2-4 hydrogenation course of, 18 6-8 equilibria, 18 7, 8 kinetic processes, 18 6, 7 experimental procedures, 18 19, 20 apparatus and methods, 18 20 materials, 18 20 mechanism of, 18 21-45 formation of isomeric decahydro-naphthalenes, 18 23-30 deuterogena-tion of - -octalin, 18 29 routes to trans isomers, 18 26-30 selectivity to trons-decalin, 18 24, 25 olefin intermediates, 18 30-45 dihydro-and hexahydronaphthalenes, 18 32, 33 analysis of products, 18 33 oc-tahydronaphthalenes, 18 34-45 analysis of products, 18 34 deu-... 

It is worthwhile to compare the stability differences of the analogous hydrindanes and decalins. In both cases, the Gibbs standard free energy differences favor the trans isomers, by 1.3 kJ mol" in the hydrindanes and by about 10 kJ mol in the decalins (94MI3). This direction of the difference is in contrast with that found for the 1,3-heteroanalogs of cis- and trans-hydrindane. 

Probtem 9.48 Decalin, C,oH,g, has cis and trans isomers that differ in the configurations about the two shared C s as shown below. Draw their conformational structural formulas. 

Sterically induced CH bond polarizations are also reflected by the shieldings of carbon atoms in crs-decalin relative to its trans isomer [230]. In the 9-methyl derivatives, steric repulsion between the methyl- and the syn-axial 2,4-hydrogens shields the attached carbon atoms relative to the parent frans-decalin. In the cis isomer, shielding of the bridgehead carbons relative to those in the trans compound clearly reflects steric interaction of hydrogen atoms in the 2,4- und 6,8-positions. 

Decalin. Decalin was chosen to study the reactivities and selectivities of and a-(5 disubstituted cyclohexane ring as well as the influence of the adjonction of a second saturated Cf, ring. The cis- and trans-isomers were photoxidized in the same conditions. The cis-isomer was found at least 10 times more reactive with a selectivity of 81% in mild oxidation products and 19% in CO2. The following relative selectivities for the main mild oxidation products (2-decalone, with small amounts of 1-decalone and 2-decalol (decahydro-2-naphtol) were found ... 

The first precise evaluation of the anomeric effect was realized by Descotes and co-workers in 1968 (22). These authors have studied the acid catalyzed isomerization of the cis and trans bicyclic acetals 6 and 6 and found that, at equilibrium, the mixture contains 57% ci s and 43% trans at 80°C. The cis isomer is therefore more stable than the trans by 0.17 kcal/mol. The cis isomer 5 has one (stabilizing) anomeric effect whereas the trans isomer 6 has none. Steric interactions in cis acetal 5 were estimated tobel.65 kcal/mol (one gauche form of ri-butane, 0.85 kcal/mol and an OR group axial to cyclohexane, 0.8 kcal/mol). By subtracting an entropy factor (0.42 kcal/ mol at 80°C) caused by the fact that the cis acetal S exists as a mixture of two conformations (cis decalin system), they arrived at a value of 1.4 kcal/mol for the anomeric effect. 

In order to test whether the base exerts an essential influence on the subsequent reaction of the carbene ligand, we also decomposed pcnta-carbonyl[methoxy( methyl) carbene chromiumfO) purely thermally at 150°C in Decalin. Under these conditions we observed exclusively the formation of carbene dimers—as a mixture of cis and trans isomers (74)— thereby confirming the influence of the base ... 

Another example is the thermal and photochemical cis-trans isomerization of Cp2Fe2(CO)2( -CO)( -Sip-TolH).25 In this case, both cis(H) and trans isomers can be isolated at full purity by flash chromatography. Interconversion between these isomers occurs both thermally and photochemi-cally in cyclohexane-d12, and the composition in the thermal equilibrium state (cis(H) trans = 2 98 at 25°C) is extremely different from that in the photostationary state (cis(H) trans = 70 30). Kinetics of the thermal isomerization in decalin afforded the activation parameters shown in Eq. (58). The large negative activation entropies imply that this reaction also... 

The decalins recovered in the product were present in the tetralin before reaction as minor impurities. The cis- and trans-isomers were fully resolved in our chromatograms and positively identified by spiking experiments with authentic samples. Material balance calculations indicate that the total amount of decalins was essentially unchanged over the course of the reaction. Hooper et al. (10) have also reported that the amount of decalin in tetralin did not change when it was heated to 450°C with coal. However, we do observe that the ratio of the trans- to cis-isomer is greatly changed and seems to approach an equilibrium value after reaction at the highest coal concentration. 

Cis-trans isomers of decalin. In trans-decalin, the two bonds to the second ring are trans to one another, and the hydrogens on the junction are also trans. In cis-decalin, the bonds to the second ring are cis, and the junction hydrogens are also cis. 

Prior to 1960 the only perhydronaphthalenes for which physical properties were available were the cis and trans isomers of decalin. Soon thereafter, our investigation of the hydrogenation of the two monomethylnaphthalenes led to the isolation, identification, and measurement of the physical properties of all eight of the resulting isomeric monomethyldecalins (5). The 68 dimethyldecalins, obtainable by hydrogenation of the 10 dimethylnaphthalenes, will be described in this contribution... 

Two kinds of mechanisms have been proposed for formation of ran -decalin. One suggestion is that trans isomers may be formed by direct trans addition of hydrogen at the two bridgehead positions. The other mechanism involves cis addition in a more complicated process that involves turning over of some sort of intermediate, with or without intervening desorption, following saturation of one of the bridgehead positions. Both routes have had support. 

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