Hydrogen/deuterium surface pool

Is the shifting hydrogen or deuterium isolated or protected from the surface hydrogen-deuterium pool And how fast does the hydrogen-deuterium pool equilibrate over the surface To partly answer these questions we consider apopinene. 

Deuterium exchange within saturated products occurs by dissociative adsorption followed by multiple stepwise migrations as described in assumption 15 followed by the addition of deuterium and/or hydrogen from the equilibrated surface hydrogen-deuterium pool. 

As inspection of Table VII shows, hexane made by reaction between 1-hexene and deuterium on chromias activated at lower temperatures is the product of at least two different surface pools of hydrogen and deuterium, one of low (D), one of high (D). Let us designate by Nt the fraction of molecules in which i atoms of hydrogen in hexane have been equilibrated with a surface pool D/H. Nq and Ni are necessarily zero since two H, D atoms must be added to hexene. Consider the runs at activation temperatures of 215 and 275°. Since Do + Di + D2 is about 70%, N2 must be large. Since Do is substantial, both added H, D atoms must involve pools in which (H) is substantial, i.e., in which (D) is low. 

Process (6). This proce.ss might be supposed nonexistent and all 2-hexcne-do to have been equilibrated with a surface hydrogen-deuterium pool of low (D ). This would require (D ) steadily to decrease... 

The second approach is that developed to interpret the products of the reactions of octalins with deuterium [144] and is equally applicable to the reactions of mono- or di-unsaturated hydrocarbons with deuterium. Smith and Burwell [144] pointed out that, whereas the experimental deuterohydrocarbon distributions are obtained in terms of the number of deuterium atoms in the product hydrocarbon, the quantities of fundamental importance to the discussion of the mechanisms of catalytic reactions are the fractions of the hydrocarbon sample which have equilibrated with the surface deuterium—hydrogen pool. Thus, for example, in the reaction of buta-1 3-diene with deuterium, the product butenes consist of a series of species, butene-(/i, d)2, -(h, d)3,..., -(h, d)n in which 2,3. .., n positions... 

Simple addition hydrogenation on sites of low (D), where (D) is the fraction of deuterium in the surface deuterium-hydrogen pool. 

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