Hexane isotopic distributions

Table VII presents the results of some of the experiments in which hexene was partially hydrogenated with deuterium, the products separated by gas chromatography, and the isotopic distribution of the hexane determined mass spectrographically on a Consolidated 21-130 instrument furnished this department under a matching grant from the National Science Foundation. An ionizing voltage of 15 V was used. In correcting for contributions of hexyl carbonium ions, it was assumed...

We had previously determined isotopic distribution patterns for alkanes derived from the deuterogenation of several olefins on an amorphous catalyst activated to 300° in hydrogen followed by activation in nitrogen to 470° (52). For reactions at about 60°, the patterns for the alkanes from j)ropylene, 1-butene, cyclopentene, and 1-hexene closely resemble those obtained for hexane from 1-hexene on amorphous catalysts in the present work that for pentane from 2-pentene resembles that for hexane from lower selectivity for alkane-d2. We consider it important that the previous work showed that ethylene led to no ethane containing more than two deuterium atoms. In the previous investigation, the effect of the temperature of... 

Phenyltin trihydride (PhSnH ). Again using the above procedure, reaction of l.Og of phenyltin trichloride (Research Chem.) and 0.60g of lithium aluminium hydride provided a hexane solution which was concentrated under nitrogen to a liquid (bp 35°C at 2.5 Torr). A portion was quickly weighed, dissolved in hexane at the g/ y1 level, and immediately diluted to a 1.0 ng/yl working standard. The neat product rapidly decomposed to a coloured, insoluble material however, the yg/ yl hexane solution gave (GC-MS) a single peak with m/e 197 (PhSn) and 120 (Sn) with correct isotopic distributions and a IR spectrum with Sn-H at 1892 cm (lit. 1880 cm ). 

The radiolysis of the protiated and the deuterated form of n-hexane and mixtures thereof has been examined as a function of temperature and at one N20-concentration. A strong isotope effect can be observed for fragmentation giving hexene and hydrogen by a unimolecular process, whereas the other product-distribution is not much affected by deuteration. N20 does not decrease the primary formation of C6Dt 3-radicals in mixtures. A novel reaction type is proposed for these systems giving hexene and water in a unimolecular step. 

Such a distribution is shown in Figure 3 for both hexanes. The figures give the approximate G-values for a particular bond, when the disproportionation is neglected. Under the condition that the dispropor-tionation/combination ratio does not change on deuteration, they can be compared for a possible isotope effect of the fragmentation yielding radicals. The probability is the same for the split of a C-H bond—e.g., 0.8 for the sum of the four C-H bonds in position 2 of hexane—but a small inverse isotope effect is observed for C-C scission. Because of the above mentioned assumptions we are unable to decide if this corresponds to reality, however such an effect would be predicted on the basis of quasi-equilibrium theory. 

In previous articles we hypothesized the existence of a high temperature back reaction of stabilized organic products with thermally activated sulfur such as S radical) (Aizenshtat et al, 1995 Krein and Aizenshtat, 1995). To experimentally evaluate this possibility we reacted, under autoclave inert conditions at 300°C, a mixture of hydrocarbons with elemental sulfur. The products and their GC/MS identification were presented in Stoler (1990). A similar experiment was performed without detailed analysis of the products distribution by Baker and Reed (1929). Most of the material polymerizes. Only 15-20% could be extracted by organic solvents (e.g. hexane or methylene chloride). The sulfur isotopes data for all products show that no isotopic discrimination occurred in this experiment (Stoler et al, 2003). All sulfur-containing isolated and identified compounds produced are thiophenes with the structure ... 

Analysis of natural abundance deuterium distribution in organic molecules, an important step in the study of kinetic isotope effects associated with enzyme-catalyzed reactions, by the use of chiral anisotropic media has been explored. An aspect of this analysis is the discrimination of the enantiotopic deuterons in prochiral molecules and the quantification of isotopic fractionation on methylene prostereogenic sites. Towards this an approach has been presented which is based on the use of natural abundance 2-dimensional NMR experiments on solutes oriented by chiral liquid crystalline solvents and the separation of the deuterium signals based on the quadrupolar interaction. The case of 1,1 -bis(phenylthio)hexane derived by cleavage from methyl linoleate of safflower has been used to illustrate the method with (D/H)pro-R and (D/H)pro-S measured at the same methylene position of a fatty acid chain. Enantiomers of water soluble materials can be observed using deuterium NMR spectroscopy in the lyotropic mesophase formed by glucopon/hexanol/buffered water. ... 

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