1-Hexene isotopic distribution

Ethene, hexenes (hexene(s) here means one unidentified Isomer) and xylenes (l.e. p-3Q lene) exhibit very different and extreme Isotope distributions. This is apparent from Figures 5, 6 and 7 which all refer to data at 400 °C. 

Figure 6. Isotope distribution In "hexene" over H-ZSM-5. Conditions as In Figure 5.

The Isotopic distribution of ethene (Figure 5) hardly changes in the temperature range 350 to 450 °C, whereas that of the hexene isomer shows a marked temperature dependence. At 350 °C it is even more biased towards the aU C-species, and at 450 °C much less so. The Isotope distribution of JQrlene also shows a small temperature dependence, but the general appearance does not change. 

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...

Isotopic distributions of toluene exchanged at 110° in runs with a deuterium/toluene ratio of 5.5 appear in Table XI. Detectable activity appeared after activation at 215°, was a maximum at about 330°, and then declined. Most runs on toluene were preceded by a run with 1-hexene and deuterium at 64°. Information on the hexene runs is contained in Fig. 10 and Tables IV, V, VII, and IX. The toluene run, 250, was followed by a run with hexene and runs 240, 247, and 10 were not connected with hexene runs. 

A run with toluene seems to have no effect upon a subsequent run with hexene and hydrogen. Run 158 of Table V was followed by a run with toluene and hydrogen. Run 158 was then repeated with very little change from the results reported in Table V. The same result was obtained in a run with benzene at 80° sandwiched between two runs with cyclopentane on a microcrystalline catalyst. This was run 280. Data on runs 288 and 290 are given in Section VII, G. The isotopic distribution pattern of the benzene was almost exactly random. 

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... 

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. 

The hexenes form besides hydrogen the largest product group in the radiolysis of the paraffins. They can be formed by Reaction 1 and by disproportionation of hexyl radicals. The decrease of their G-value on deuteration is 1.5, the corresponding decrease of G( molecular hydrogen) is 1.6. This is additional proof for an isotope effect for Reaction 1. This reaction explains also the observation that the isomeric distribution of... 

In the isotope experiment, the stereochemistry of the insertion is different, depending on whether a-H or a-D agostic interaction is involved. If an isotope effect is found, agostic transition states are indicated. For example, Kraule-dat and Brintzinger [69a,b] have shown that in hydrodimerization of deuter-ated 1-hexene with methylaluminoxane (MAO)-activated zirconocene dichloride (Cp2ZrCl2) the product distribution is consistent with an a-agostic assisted insertion (Eq. 2.24). 

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