Decalins, isomerization

The changes in the product concentrations are more pronounced in case of Pt-zeolites. Particularly the rate of decalin isomerization is considerably enhanced by the addition of platinum. The ratio of Iso/ROP decreases from the value of 12 after 1 h to the value of 1.4 after 9 h. The ratio of ROP/CP decreases from the values close to 3 within the first 3 h to the value of 1.3 after 9 h. This is in contrast to H-Beta-25, where the ratio ROP/CP is almost constant during the entire experiment and its values do not exceed 1.5. The same trends are... 

Antimony pentafluoride, inserted into graphite to form the first stage insertion compound, is a mild and efficient solid superacid catalyst for the isomerization of alkanes to a thermodynamic equilibrium mixture at or below room temperature. Thus an equilibrium mixture of cyclohexane and methylcyclopentane (91 9) was obtained from either of the pure hydrocarbons, and ci5-decalin isomerized almost completely to the frarw-isomer. ... 

Use ) gui to produce the cis and i/rms forms of decalin. Run a PM.f calculation of the energies of these two forms. What is the cis-lmns isomerization energy as calculated by PMIT ... 

The isomerization observed in the methylenation of c/s-a-decalones has been turned to good advantage. Mixtures of cis- and tra/is-isomers of the a-decalones (44) and (46) gave only the /ra/i -decalins (45) and (47). 

The complexity of skeletal isomerization of decalin is depicted in Figures 8A and 8B. It shows that methylbicyclo[4.3.0]nonanes (MBCN1) are the... 

Tetralin. Therefore, either trans-Decalin was formed on the surface of the coal with deuterium from the solvent or gas, or it was formed by isomerization from cis-Decalin with accompanying isotopic exchange with a deuterium source. Because the protium content of the cis-Decalins is much greater than the trans-Decalins, cis-trans isomerization is not very important. 

Fig. 15 A proposed reaction network of direct ring opening of decalin reaction over acidic zeolites. PC Protolytic cracking HeT Hydride transfer HT Hydrogen transfer I Isomerization P /i-scission DS Desorption TA Transalkylation. Adapted from ref. 47.

Kubica et al45 also investigated the effect of platinum-modified zeolites on the decalin reaction. They found that the addition of Pt enhances the catalyst activity. The initial isomerization was increased 3 times, which can be interpreted in terms of a change in the reaction initiation. In addition to initiation by a PC step over Bronsted acid sites, as proposed for H-form zeolites, a bifunctional initiation path... 

Since the theory of strainless ring put forward by Sachse required the existence of two isomeric forms and since all attempts to find them had failed the theory was not given much importance till 1918 when Mohr explained the absence of the two forms because of their rapid interconversion. This rapid interconversion can be beautifully illustrated on models where no considerable effort will be needed. Mohr also pointed out that the union of two cyclohexane rings may result in the formation of cis and trans decalins. 

Fig. 29 Formation of isomeric decalins [71 ]—[73] by cyclization of a terpenoid alcohol catalysed by antibody HA5-19A4 raised to hapten [82]. The transition state [83a] has the leaving group in the equatorial position, as favoured by the Stork-Eschenmoser...

All solvents for these solution thermolysis reactions were freshly distilled and all reactions were done in sealed glass tubes heated in a thermostatted oven. Over a wide range of solvents (DMF, naphthalene, diphenylmethane, benzene, toluene, and decalin) there was no significant variation in either isomerization rate or product composition. Reactions were done at 125°C, 155°C and 195°C and the only limitation was that DMF could not be used as the solvent in reactions at 195°C it led to substantial substrate destruction (polymer forming reactions of substrate with DMF ). Isomer compositions were ascertained both by HPLC and by NMR. 

Dealkylation, heteropoly compunds, 41 160-161, 170-174 Deamination, 27 259 Pd(NH3>/ ions, 39 142 Debye-Waller factor, 21 177 Decahydronaphthalenes conformation of, 18 17-19 isomeric, formation of in hydrogenation of naphthalenes, 18 23-20 rrans-Decalin... 

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-... 

Similarly Smith and Burwell (61) concluded that desorbed -octalin is a common intermediate in the formation of cis- and hydrogen-deficient species, possibly an allyl-77- complex (see Section III,C). 

Becanse of the high concentration of isomeric molecules (>0.1 mol dm ), this equilibrium is established instantaneously. The IP of trans-AtcaYm is 0.02 eV lower than the IP of cw-decalin (9.24 eV versus 9.26 eV). Therefore, the electron-transfer eqnilibrinm is shifted slightly to the left side. Thns, in terms of charge-transfer kinetics, the two ions behave as a single species. It shonld be worth noting that decalin has only two isomeric forms, cis and trans. On the contrary, n-nonane exists in the multitude of conformations. The rate constant of electron exchange between parent nentral molecules of nonane and its cation-radicals is much lower, namely, 2 orders lower than the diffnsion-controlled limit (Borovkov et al. 2007). 

Isomeric l,3a,4,6a- (220) and l,3a,6,6a- (91) dibenzotetraazapentalenes can be prepared from the thermal decomposition of 2-((9-azidophenyl)-2//-benzotriazole (224) and - o-azidophenyl)-2//-benzotriazole (230), respectively, in high boiling solvents such as 0-dichlorobenzene and decalin. This synthesis was improved upon when it was found that (220) and (91) can be prepared from the reactions of 2-((9-nitrophenyl)-2//-benzotriazole (226) and l-(o-nitrophenyl)-2//-benzotriazole (229), respectively, with triethyl phosphite in refluxing xylene. ... 

Perfluoro- 1,3- dimethyl- cyclohexane Perfluoro- n-octane Perfluor- decaline (cis+trans Isomere) Perfluoro- perhydro- phenan- threne... 

The nearly equal amount of cis and trans products formed from 1,5-dimethylcyclo-hexene is explained by the almost equal degree of hindrance of the homoallylic methyl group with the catalyst surface in the alternate adsorption modes.63 64 Another interesting example is the platinum-catalyzed hydrogenation of isomeric octalins.65-67 If syn addition to the double bond is assumed, in principle, both cis- and mms-decalin are expected to result from l(9)-octalin, but only the cis isomer from 9(10)-octalin. In contrast with these expectations, the isomers are produced in nearly the same ratio from both compounds. Transformation in the presence of deuterium revealed that most of the products contained three deuterium atoms. This was interpreted to prove that the very slow rate of hydrogenation of 9(10)-octalin [Eq. (11.9)] permits its isomerization to the 1(9) isomer. As a result, most of the products are formed through l(9)-octalin [Eq. (11.10)] ... 

Detailed studies have been conducted on the selectivity of hydrogenation of naphthalene.67 The reaction proceeds via tetrahydronaphthalene as an intermediate and eventually yields a mixture of the isomeric decalins ... 

Good selectivities for m-decalin are exhibited by all platinum metals except palladium that is unique in the high yield (52%) of trans-decalin 66,67 It was proved that isomeric octalins are involved in determining product selectivities66,67 (see Section 11.1.2). 

When a mixture of cis- and frares-decalins 24 (61.5 38.5) are treated with the same solid superacid at 0°C, the thermodynamic equilibrium is rapidly achieved110 [Eq. (5.48)]. In the reaction, decalin 24 serves as the solvent, substrate, and the hydride donor. When the equilibrium is reached, the hydrocarbon can be separated from the catalyst by simple filtration. Perhydroindane 25 was also isomerized under... 

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